Glossary of Automotive Terms – P

Letter P – Dictionary of Automotive Terms

  1. A tire designation for Passenger, as used in rating tires such as P185R13.
  2. A tire designation for speeds up to 150 kph (95 mph) as in P195PR78 (the first P is passenger, but the second P is the Speed rating.
  3. The designation for park on the gear selector of an automatic transmission.

  1. Abbreviation for Pressure Air (Honda)
  2. Abbreviation for Power antenna.
An abbreviation for Power-assisted
Abbreviation for Pickup and delivery
Pace car
A vehicle which leads the pack of racers during the first part of the race (usually one lap) so that the racers can warm up their engines, etc. The pace car never runs the actual race. They also lead during parade, pace lap, caution periods, and restarts.
Pace lap
The warm-up part of the race before the actual race begins.
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An automobile manufactured by AMC

Package units
Complete refrigerating system including compressor, condenser, and evaporator located in refrigerated space.
PackardClick image for books on

A vehicle brand of which several models with required application are classic cars:

  • 1925-34 all sixes and eights
  • all 12-cyl. models
  • 1935 Models 1200-1208
  • 1936 Models 1400-1408
  • 1937 Models 1500-1508
  • 1938 Models 1603-1608
  • 1939 Models 1703-1708
  • 1940 Models 1803-1808
  • 1941 Models 1903-1908
  • 1942 Models 2004-2008 plus 2023
  • 1946-47 Models 2106 and 2126
  • all Darrin-bodied models

The following models are milestone cars:

  • 1953-56 Caribbean models
  • 1946-50 Clipper and Custom Eight
  • 1954 Pacific sedan and convertible
  • 1954 Panther Daytona
  • 1951-56 Patrician 400
A cylindrical recess that accommodates a number of rings of packing around the shaft or shaft sleeve of a pump. Pumps used for high-temperature fluids are provided with jacketed, water-cooled packed glands. Also called stuffing box.
Sealing device consisting of soft material or one or more mating soft elements. Reshaped by manually adjustable compression to obtain or maintain a leak-proof seal.

Pack muffler
Abbreviation for Program Associated Data.
A common term for a brake shoe used in disc brakes

Abbreviation for Petroleum Administration for Defense Districts
Padding disc
An insert in the crankcase area designed to reduce the internal volume of the crankcase and thus to increase the precompression ratio; this helps to increase the output of a two-stroke engine
Paddling the lead
The act of filling repair areas by smoothing the body lead layer until a smooth surface is achieved
Pad retainer
A pin which locates the brake pad in a disc brake
Pad retainer pin
A pin which locates the brake pad in a disc brake
Pad Sets
Pad wear indicator
Mechanical or electrical devices which warn the driver when the lining material on the brake pads has worn to the point that they should be replaced.

Abbreviation for Pulse Air Feeder System (Chrysler)
Pagoda roof
An unusual roof design, introduced on the Mercedes-Benz SL Hardtop, which was slightly lower in the center than at the sides
Pagoda-style roof
An unusual roof design, introduced on the Mercedes-Benz SL Hardtop, which was slightly lower in the center than at the sides
  1. Abbreviation for Polycyclic aromatic hydrocarbons
  2. Abbreviation for polyaluminum hydroxide
  3. Abbreviation for Polynuclear Aromatic Hydrocarbons
Paid value
  1. A liquid or paste consisting of a suspension of a Pigment in oil or water, etc. When spread over a surface, it dries to form a hard, thin covering colored by the pigment. The primary purpose of paint is to help in the preventing of rusting. A secondary purpose is to provide a variety of color.
  2. The act of spray painting a surface.
Paint booth
A closed area where coats of paint are applied
Paint chip book
A Color chart
Paint color matching
The process of determining the correct paint shade with the aid of color charts and special mixing devices and through spectral analysis
Paint film
The actual thickness of the paint on a surface.
Paint gun
Painting line
The route taken by the bodywork of a newly manufactured vehicle on its way through the paint shop
Painting robot
A robot used for paint application
Paint refinishing
The various steps involved in repainting a secondhand car
Paint shop
  1. The production stage in an automobile manufacturing plant during which the bodywork is treated with paint.
  2. A separate paint repair shop, usually near a body repair shop (i.e., for damaged vehicles)
Paint stripper
A liquid paint remover
Paint system
The sum of all coats of paint on a work
The overall result of painting; the paint coating or finish
Abbreviation for Pulsed Secondary Air Injection
PAIR system
A white, ductile, malleable, noble metal of the platinum family; atomic number 46, atomic weight 106.4; resembles platinum and together with other platinum metals is used as a catalyst in automotive exhaust converters. Compare Platinum metals
A portable platform (usually made of wood or rarely plastic) on which goods can be placed. It is constructed with spaces between the top and bottom layers so that the prongs of a forklift can be inserted to lift the pallet with its goods in order to move, stack, and store them.

Palletized construction
The process of building a vehicle where the workers assemble a complete chassis at a comfortable workbench height, in a well-lighted area, away from the main line — not underneath a moving body. Working conditions and product quality are vastly improved.
Palm spinner
Palm spinnerPalm spinner

A device which is attached to a steering wheel to allow disabled people to insert a hand into its bracket in order to steer a vehicle.

A thin stamped cover that is bolted to the bottom of the crankcase, it forms a sump for the engine oil and keeps dirt, etc. from entering the engine.

Panama Chock
A steel casting used for line handling: from one vessel to another vessel or to the dock. Developed for use in the Panama canal.
A water-borne vessel (i.e., ship) designed small enough for passage through the Panama Canal
Pancake engine
An engine in which the cylinders are on a horizontal plane, this reduces the overall height and enables them to be used in spots where vertical height is restricted.

Pan drain plug
A sheet of window glass
  1. A flat piece of metal that is stamped to create a body component such as a door panel.
  2. A plastic molding; e.g., interior trim of doors.
Panel beater
  1. A person who beats out the dented bodywork of a damaged vehicle.
  2. A Panel hammer
Panel beating
Beating out the dents in damaged bodywork.

Panel bonding
A new repair process using a special adhesive to glue body panels in place instead of spot-welding them
Panel contour
The normal shape of a new, undented body panel as produced by the factory
Panel cutter
An air-operated tool used to cut out old panels. It is a relatively coarse tool and is thus suited mainly for cutting sheet metal in areas where minor distortion along the cutting lines does not matter.

Panel Deck Pallet
A pallet constructed with composite or structural panel top deck.
Panel file
Panel flanger

Panel hammer
A special hammer for metalworking that has two different fly-shaped heads for different purposes, e.g., cross-pein and shrinking hammer.

  1. A combination of separate sheet metal panels to form a complete assembly, e.g., the outer panels of the body or even the panels surrounding the engine
  2. A plastic molding; e.g., interior trim of doors.
Panel picking
The act of straightening very fine indentations or marks of very small diameter on a panel surface with a pick hammer
Panel puller
Dent PullerSlide Hammer Dent Puller

A tool with a slide hammer and hook or self-threading screw tip to pull dented doors, fenders, and other sheet metal panels back into place. After drilling a hole in the deepest part of the dent, the hook or screw tip is inserted to pull out the dent by means of slide hammer impact. Also called Knocker

Panel release tool
Panel repair
A type of repainting job involving an entire panel but not the entire vehicle
Pan gasket
Pan guard
A vehicle brand of which the Dyna for 1946-67 models are milestone cars.
Panhard rod
A rod or linkage on the axle which runs from side to side. Usually one end is attached to the body and the other end is connected to the axle. Also called a track bar.
Panhard rod mounting box
Box section used to mount the Panhard rod of the rear axle
Harley-Davidson’s second generation overhead-valve Big Twin, introduced in 1948.
Pan head
A type of screw with a dome shaped head. Flat top surface rounded into cylindrical sides, and a flat bearing surface. The recessed pan head has a rounded top surface blending into cylindrical sides and a flat bearing surface.
A luggage bag used in pairs and fastened alongside one or both wheels of a motorcycle or bicycle.


Luggage bags used in pairs and fastened alongside one or both wheels of a motorcycle or bicycle.

Panoramic windshield
A windshield style popular in the 1950s and ’60s that featured recessed screen pillars, giving a wide, unobstructed view of the road; entry for the front passengers was awkward, since the screen pillar comers projected into the door opening
P. ant
Abbreviation for Power antenna.
A British term for a large van or truck, especially one for moving furniture
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A model of automobile manufactured in Italy

The pulsation in and out of the bow and stern plating as the ship alternately rises and plunges deep into the water
Panting frame
The frames in the forward and after portions of the hull framing to strengthen against shell Panting
Paper air cleaner
An Air cleaner that makes use of special paper through which the air to the carburetor is drawn.
Abbreviation for a parabolic aluminized reflector lamp
Parabolic dish
A high-temperature (above 82°C) solar thermal concentrator, generally bowl-shaped, with two-axis tracking.

Parabolic reflector
An old headlight reflector in the shape of a parabola, now replaced by ellipsoidal reflectors
Parabolic spring
A leaf spring tapered in the shape of a parabola. Also called tapered leaf spring
Parabolic trough
A high-temperature (above 82°C) solar thermal concentrator with the capacity for tracking the sun using one axis of rotation.

  1. A British term for Kerosene a solvent for removing grease
  2. A light-colored, wax-free oil obtained by pressing paraffin distillate.
  3. The wax removed from paraffin distillates by chilling and pressing. When separating from solutions, it is a colorless, more or less translucent, crystalline mass, without odor and taste, slightly greasy to touch, and consisting of a mixture of solid hydrocarbons in which the paraffin series predominates.
Paraffinic hydrocarbons
Straight-chain hydrocarbon compounds with the general formula CnH2n+2.
Group of saturated aliphatic hydrocarbons, including Methane, ethane, Propane and Butane and noted by the suffix -ane.
  1. The same distance apart at every point.
  2. Two or more electrical components each receiving the same voltage resistors connected in parallel. Opposite to Series.
  3. To connect in parallel
Parallel action locking pliers
A locking pliers with parallel action jaws, e.g., for pinching off hoses when servicing cooling systems
Parallel circuit
  1. An electrical circuit with two or more resistance units so wired as to permit current to flow through both units at the same time. Unlike the Series circuit, the current in the parallel circuit does not have to pass through one unit to reach the other. A method or pattern of connecting units in an electrical circuit so that they are connected negative-to-negative and positive-to-positive. In a parallel circuit, current can flow independently through several components at the same time.
  2. Arrangement of electrical devices in which the current divides and travels through two or more paths and then returns through a common path.
Parallel connection
A way of joining photovoltaic cells or batteries by connecting positive leads to positive leads to keep the voltage output the same, but increase the amperage. Some 12-volt vehicles running two batteries to give more winter starting power must connect the batteries in parallel. If they were Connected in series the output would be 24 volts and fuses would blow or components would burn out.
The same thickness of brake discs all the way around. The relationship between one friction surface of a brake disc and the other.

Parallel key
Parallel middle body
The amidships portion of a ship in which the contour of the underwater hull form is unchanged
Parallelogram steering
Parallelogram steering linkage
Parallelogram steering linkageParallelogram steering linkage

A Steering system using two short Tie rods connected to the steering arms and to a long center link. The link is supported on one end on an idler arm and the other end is attached directly to the pitman arm. The arrangement forms a parallelogram shape.

Parallelogram steering system
Parallelogram suspension
Parallel parking
The action of bringing a vehicle to a stop behind another vehicle (or between two vehicles) so that your front bumper is right behind the rear bumper of the vehicle in front of you. The technique of parallel parking involves driving beside the other vehicle and then backing up while turning the steering first to the right and then at the correct time turning it to the left. It is one of the testing requirements for obtaining a license.
Parallel trailing link suspension
A front suspension layout used primarily by Volkswagen on rear-engined cars
Parallel twin
A type of engine usually found on two-cylinder motorcycles where the cylinders are beside each other and on the same side of the crankshaft. An Opposed twin has two cylinders that are on either side of the crankshaft.
Parallel-twin engine
A two-cylinder engine with its cylinder placed side-by-side in an upright position
Parallel valves
The intake and exhaust valves with parallel valve stems
Concrete rails on a bridge.
Parent panel
The panel left in place on the car to which a new panel is welded after all the rusted metal has been cut out
A short length of glass

  1. One of the positions of the gear selector for an automatic gearbox; when engaged (after the vehicle has come to a complete standstill) the driving wheels are locked.
  2. To leave a vehicle in a particular place.
  3. A Parkade.
A place where vehicles can be parked on one of several levels.

Park and Ride
Provision of long stay parking areas at the edge of a built up area which are linked by frequent bus (or other public transport) services to the City center and potentially other locations.
Park Avenue
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Park Avenue

A model of automobile manufactured by the Buick division of General Motors from 1991-2005

Park brake
Park brake extension
Park brake extensionPark brake extension

A device which is attached to the parking brake to help disable people to operate the parking brake more easily.

Parkbrake warning light
A light on the instrument panel that illuminates when the parkbrake is applied; on most new cars it has been superseded by a multifunction brake warning light
The action of placing a vehicle at a full stop out of the flow of traffic.

Parking brake
  1. Hand or foot operated brake which prevents vehicle movement while parked by locking rear wheels, or transmission Output shaft. One type applies the rear brake shoes by mechanical means and the other type applies a brake band to a Brake drum installed in the Drivetrain.
  2. The secondary brake system used to hold a stationary vehicle from moving. The system is applied with a hand or foot lever, and operates on only two wheels.
  3. The mechanically actuated portion of a drum brake or disc brake caliper, used to prevent the vehicle from rolling when it is parked, applied by a lever, pedal, or rod
Parking-brake cable
Cables that transmit brake actuating force in the parking-brake system.
Parking brake console
The reinforcing member incorporated in the center tunnel area of the floorpan to provide the mounting support for the handbrake
Parking-brake equalizer
A device to equalize pull between the parking-brake actuator and two wheels.
Parking brake lever
  1. A lever inside the drum brake which spreads the brake shoes outward; the long end is connected to the parking brake cable, the opposite end to one brake shoe and to a push bar which acts on the other shoe.
  2. A lever inside the passenger compartment attached to the end of the parking brake rod and which activates the parking brake cable.
Parking brake lever strut
A push bar between the shoes in a drum brake
Parking brake pedal
Foot-operated pedal for the parking brake
Parking brake warning switch assembly
A unit used to actuate a warning device indicating the parking brake application mechanism is not in the fully released position.
Parking disc
A marker displayed on the inside of a parked car showing time of arrival or latest permitted time of departure in a British parking lot
Parking distance sensor
A device which indicates to the driver how close the car is to the curb and/or to objects in front or behind. The early form of detector was a flexible antenna which protruded from the side of the car and attached to the wheel well. When the vehicle was too close to the curb, it scraped along its edge making a loud scratching noise warning the driver. The current model is an electronic sensing device which detects the distance the car is from a particular object (i.e., parked car, tree, garage door, person) and relays that information on a screen located on the dash. Some types relay the information through a vocal output.
Parking heater
An air heating system which operates independently of the engine
Parking interlock
Parking lamp
An energy-saving vehicle illumination mode on British cars for long-term roadside parking; includes only one front sidelight and one taillight; the parking light can be switched to illuminate the left side or the right side
Parking light
An energy-saving vehicle illumination mode on British cars for long-term roadside parking; includes only one front sidelight and one taillight; the parking light can be switched to illuminate the left side or the right side
Parking lock
(PL) A lock gear and pawl that lock the transmission mechanically
Parking lot
A ground level, outdoor area where vehicles can be left temporarily.
Parking lot stencil
A printing device which is placed on the ground so that information like handicap parking signs can be made.
Parking meter
A coin-operated timing device that indicates how long a vehicle may legally remain parked
Parking space
A parking place reserved for a particular vehicle
Parking ticket
A written fine for a parking offence, especially where a vehicle has exceeded the time limit for parking
Park light
A low intensity light which is often incorporated into the front signal lights. The park lights are to be illuminated when the vehicle is still running, but pulled off the road. However, many people drive with them on — an action which is illegal in some parts of North America.
Park safety switch
A switch which allows the starter to be engaged only when the automatic shift lever is in either park or neutral
A component of a vehicle.

Partial flow filter
A Bypass filter
Partial oxidation
Fuel reforming reaction where the fuel is partially oxidized to carbon monoxide and hydrogen rather than fully oxidized to carbon dioxide and water. This is accomplished by injecting air with the fuel stream prior to the reformer. The advantage of partial oxidation over steam reforming of the fuel is that it is an exothermic reaction rather than an endothermic reaction and therefore generates its own heat.
Partial oxidation burner
Heat source for the partial oxidation reactor.
Partial pressures
Condition where two or more gases occupy a space and each one creates part of the total pressure.
Partial respray
A respraying of only part of the bodywork, opposite to Full respray or Complete respray
A small, discrete mass of solid or liquid matter that remains individually dispersed in gas or liquid emissions. Particulates take the form of aerosol, dust, fume, mist, smoke, or spray. Each of these forms has different properties.

Particulate catalyst
A Pellet catalyst
Particulate emission
An emission of solid particles of carbon and unburnt hydrocarbons from the exhaust system
Particulate emission limit
The weight of particulate emissions in the exhaust of diesel engines, specified in grams per mile
Particulate filter
Particulate ignition temperature
In diesel filtration tests, the exhaust gas temperature at which there is an equilibrium between particulate burn-off and deposit build-up
Particulate matter

  1. Suspended solids of carbon and unburnt hydrocarbons from the exhaust system
  2. A generic term for a broad class of chemically and physically diverse substances that exist as discrete particles (liquid droplets or solids) over a wide range of sizes. A NAAQS pollutant.
  3. Particles formed by incomplete combustion of fuel. Compression ignition (diesel) engines generate significantly higher PM emissions than spark ignited engines. The particles are composed of elemental carbon, heavy hydrocarbons (SOF), and hydrated sulfuric acid (sulfate particulates).
  1. (PM) Suspended solids of carbon and unburnt hydrocarbons from the exhaust system
  2. Small pieces (particles) of matter; dust is a common particulate.
Particulate Trap
Diesel vehicle emission control device that traps and incinerates diesel particulate emissions after they are exhausted from the engine but before they are expelled into the atmosphere.
The throttle opening between idle and fully open
Part-load enrichment
Extra fuel injected during throttle opening to enrich the mixture during transition. Usually occurs during closed-loop operation
Part-load operation
The operation of systems and components under conditions below full load
Business owned by at least two people
Partnership for a New Generation of Vehicles
(PNGV) established in 1993, this partnership, between the United States Federal Government and the Automotive industry, was founded to establish global technical leadership in the development and production of affordable, fuel-efficient, low emission vehicles that meet today’s performance standards.
Part number
(p/n, PN) A reference number attributed to a particular part. Each company uses its own system of numbering the parts.
Part out
To dismantle a vehicle and sell the parts. British term is break up
Part panel
Parts car
A vehicle that has been damaged beyond repair or Restoration, or that has deteriorated badly. It is useful only as a source of parts. It may be Driveable though unsafe, but it usually is not in driveable condition.
Parts catalog
A directory listing available parts for a particular product
Parts per million
(ppm) Unit of concentration of one element in another.
Parts store
Part Throttle
Part-throttle operation
Driving without using full throttle
Part-time four-wheel drive
A manually selectable four-wheel drive
  1. Abbreviation for Power-assisted steering
  2. Abbreviation for Passive Anti-Theft System
Pascal (pa)
SI measurement of pressure, it equals one newton per square metre.

Pascal’s law
A principle which states that when pressure is exerted on a confined liquid, it is transmitted undiminished. The law is particularly valid for hydraulic systems. Discovered by Blaise Pascal (1623-1662)
PA sensor
Abbreviation for Atmospheric pressure sensor
  1. The act of overtaking a vehicle which is traveling in the same direction you are.
  2. The act of going past a vehicle which is traveling is the opposite direction from you.
  3. Weld metal created by one progression along the weld.
  4. Abbreviation for Personalized Automotive Security System

Passenger capacity
The maximum number of people that a vehicle can carry.
Passenger car
A four-wheeled motor car powered by an engine and designed for passengers and/or their luggage.

Passenger car wheel
A one-piece wheel made of sheet steel. The rim and disc are welded together or made of light-alloy (cast or forged), and designed for tubeless tires. Rims for passenger cars are almost exclusively designed as 5° drop center rims incorporating a safety bead seat (double hump and combination hump are most common; flat hump designs are less common) and a J-flange. The B-flange type is reduced in height and used on passenger cars with small rim diameter and rim width
Passenger cell
That part of the vehicle in which the driver and passengers sit
Passenger compartment
That part of the vehicle in which the driver and passengers sit
Passenger-miles traveled
The total distance traveled by all passengers. It is calculated as the product of the occupancy rate in vehicles and the vehicle miles traveled.
Passenger ship
A ship authorized to carry more than twelve passengers.
Passenger-side air bag
An air bag restraint system designed to protect the front passenger; introduced on some cars in the early 1990s, it usually occupies the space normally provided for a glove compartment
Passenger vehicle
Four wheeled motor vehicle that also includes mini-vans and sport utility vehicles.
  1. The action of overtaking another vehicle going in the same direction you are.
  2. The action of going past another vehicle which is going in the opposite direction you are.
Passing gear
An automatic transmission gear that shifts a vehicle into a lower gear for a short burst of extra power to pass other cars on the highway. The gear is engaged by sharply depressing the gas pedal. When the pedal is released, the vehicle returns to normal to normal driving gear.

Passing lane
The outside lane (far left lane in North America, etc. or the far right lane in Britain, Australia, etc.). Also called the fast lane
  1. To reduce the reactivity of a chemically active metal surface by electrochemical polarization or by immersion in a passivating solution
  2. A process of surface treatment for neutralizing stainless steels. An oxydizing solution, such as nitric acid is applied to the surface. This strengthens the normal protective film which helps in resisting corrosion. It also removes any foreign substance which might cause local corrosion.
  1. Technical definition: a process of dipping a metal object into a nitric acid solution to rapidly form a chromium oxide on the surface of the material, creating a passive film that protects stainless from further oxidation called a passive film. The purpose of passivating is to remove both grease left from manufacturing and traces of steel particles which may have rubbed off manufacturing tools onto the object. Contrasts with commercial definition of cleaning.
  2. Commercial definition: cleaning. A wide range of cleaning methods using different mixtures containing nitric, phosphoric and other acids or simply exposing cleaned stainless objects to air for a period of time will result in a ‘passivated’ condition. For metal objects that have been properly cleaned, it is impossible to determine the method of cleaning or passivation that was used.
Passive film
The major characteristic of stainless steel is its ability to form a thin layer of protection, called a ‘passive film,’ on its outside surface. This film results from a continual process of low-level oxidation, so oxygen from the atmosphere is needed for the passive film to exist. Once formed, it prevents further oxidation or corrosion from occurring. Even if chipped or scratched, a new passive film on stainless will form.
Passive restraint system
Passive safety
Any device which automatically provides protection for the occupants of a vehicle such as the bumpers, seat belt, padded instrument panel, Laminated windshield, head restraints, collapsible steering column, air bags, etc. In contrast with Active safety.
Passive safety features
Items in a vehicle which do not require action on the part of the driver to avoid a hazard, e.g., crumple zones, bumpers, side impact beams, and roll-over bars.

Passive solar heating
A solar heating system that uses no external mechanical power, such as pumps or blowers, to move the collected solar heat.
Passive state
A state for the fuel cell internal components normally entered when the power plant is purged with steam, air or nitrogen, or per the manufacturer’s instructions when the power plant is turned off or prior to when the power plant is turned on (initialization).
Honda PassportClick image for books on
Honda Passport

A model of automobile manufactured by Honda

  1. To repair a component.
  2. The added part used to repair a component, e.g., a rubber disc glued to a tube to cover a nail hole.
  3. The footprint of a tire in its contact with the ground.
Patch cutting method
A silvicultural system in which all merchantable trees are harvested over a specified area at one time.
  1. A repair method for welding up local corrosion damage by using smaller panels made up from sheet metal.
  2. A repair method for gluing a rubber patch to a tube which has a hole in it.
Patch panel
A small sheet metal panel that is usually made up specially to repair minor rust holes
PathfinderClick image for books on

A model of SUV manufactured by Nissan in Japan

Pattern Nuts
Special nuts usually furnished in plain or chamfered face unless otherwise specified, and threads are unified Coarse or unified Fine, Class 2B. (also small and extra small)
Pattern panel
A body panel made by somebody other than the original manufacturer, usually for repair purposes; this also includes panels remanufactured after the factory has discontinued making and supplying those parts.
Pattern percentage
Pattern snips
Pavement markers
Three-dimensional markers, reflectorized or non-reflectorized, epoxied onto pavement.
Pavement markings
Traffic markings such as lines, arrows, bicycle symbols, and words like ‘only’ and ‘school’.
  1. A bar, pin, or Stud that can be moved, pivoted, or slid into engagement with teeth cut on another part, such as the parking pawl on the automatic transmission that can be slid into contact with teeth on another part to lock the rear wheels.
  2. A catch at the bottom of a lever which connects with a toothed rack to hold the lever in position (e.g., with a handbrake lever or in ratchets).
  3. An arm pivoted so that its free end can fit into a notch, slot, or groove at certain times in order to hold a part stationary
  1. The actual weight of cargo being carried, including packaging, etc. (GVW — Unladen weight = payload).
  2. The revenue-earning cargo of a commercial vehicle.


  1. Abbreviation for Power brakes
  2. Abbreviation for Pushbutton as in PB radio.
  1. Abbreviation for Pitch circle
  2. Abbreviation for Polycarbonate
  3. Abbreviation for Pressure Control
  1. Abbreviation for Printed circuit board
  2. Abbreviation for Polychlorinated biphenyl. Difficult to remediate chemical used in old-style transformers. Concentrated PCBs used to be referred to as 1268.
Abbreviation for Pitch circle diameter
  1. Abbreviation for Program comparison and identification
  2. Abbreviation for Programmable Communications Interface
Abbreviation for Powertrain Control Module A computer that controls the operation of the engine’s fuel, ignition, and emission-control systems as well as the transmission on vehicles with automatic transmission.
Abbreviation for Powertrain control module
Abbreviation for Pressure Control Solenoid
Abbreviation for Positive crankcase ventilation.
PCV system
Abbreviation for Positive crankcase ventilation system. A system which prevents crankcase vapors from being discharged directly into the atmosphere.

Abbreviation for Positive crankcase ventilation valve
PCV valve
(PCVV) Part of the Positive crankcase ventilation system, which reroutes crankcase Blowby to the intake manifold and back to the engine, where it is reburned in the cylinders as part of the fuel-air mixture. This cuts emission pollution and improve fuel economy because unburned fuel in the Blowby is consumed the second time around. It also keeps the Blowby and water vapor from fouling the oil in the crankcase, thus reducing the formation of engine Sludge.
Abbreviation for Pickup and delivery


Abbreviation for Personal Digital Assistant.
Abbreviation for power disc brakes.
Abbreviation for power door locks.
Abbreviation for power deck lid release.
Abbreviation for power deck release.
  1. Abbreviation for Power Enrichment
  2. Abbreviation for Polyethylene
  3. Abbreviation for Polyellipsoidal
A condition, usually in the cushion rubber, resulting from local material starvation and excessive flow from adjacent areas.
Peak inverse voltage
Amount of voltage a diode can take in reverse direction without being damaged
Peak power
The point of maximum torque
Peak pressure period
The phase of diesel combustion lasting from about five degrees before top dead center to about 10 degrees after top dead center, the majority of diesel fuel burns during this period
Peak revs
The point of maximum engine speed
An engine that is able to deliver useful power only at high revs and needs frequent shifting. Compare Flexible
A small motorcycle fuel tank which holds about five litres (one gallon) usually found on a Chopper.
Abbreviation for Power Enrichment Control Valve
A lever operated by the foot. It is distinguished from a footplate. A footplate allows you to rest your foot, but no action takes place. However, when you place your foot on a pedal, some action could take place.

Pedal clearance
The distance between the pedal and the floor, when the pedal is fully depressed; reference points may vary
Pedal cleats
An attaching bracket secured to the sole of a cycling shoe. The cleat locks into the body of the pedal holding the foot securely. Cleats are supplied by the pedal manufacturer.
Pedals, clipless
Pedal float
The amount that the pedal cleat can spin while still clipped into a Clipless pedal
Pedal free play
The distance a pedal moves until a slight resistance is felt.

Pedal free travel
Pedal, platform
Pedal play
Pedal pulsation
The vibration of the brake pedal when depressed, caused by a defective disc or drum (or when ABS is activated)
Pedal ratio
On a brake pedal, the ratio of foot pedal travel to pedal pushrod travel.
Pedal reserve
The amount of brake pedal travel still available when the brakes are applied.
Pedal, toe clip
Pedal to the metal
To fully apply the accelerator for a fast take-off.
Pedal travel
The total stroke of a pedal, i.e., the distance the pedal moves

Peddle Run
A truck route with frequent delivery stops
Pedestal pivot
A semi-cylindrical (half-round) pivot used with pivot guided rocker arms. A pedestal pivot restricts the rocker arm so it pivots around one axis or in a single plane-the plane of the valve stem and pushrod
Pedestrian refuge
Island for pedestrians located in the carriageway.
  1. The action of rapid acceleration so that the tires slip on the road surface (i.e., the wheels are turning, but the vehicle is not moving very much) which may result in a strip of rubber on the road surface.
  2. The action of paint coming off.
A method of separating a bond of two flexible materials or a flexible and a rigid material that have been bonded with an adhesive. The flexible material is pulled from the mating surface at a 90 or 180 degree angle to the plane in which it is adhered. The stress is concentrated along the line of immediate separation. Strengths are expressed in pounds per inch width (piw)

Peel rubber
Rear wheels slipping on the highway during acceleration. Also called Burn rubber.
Also spelled pein

  1. To flatten out the end of a Rivet, etc., by pounding with the round end of a hammer.
  2. The ball-shaped, or narrow wedge-shaped end of a hammer head opposite the flattened striking face.
Peen hammer
Also spelled pein hammer. A body hammer with a peen of triangular section with a fairly sharply shaped end.

  1. The flattening or shaping with a peen hammer.
  2. The stretching of metal by hammering or rolling the surface.
A vehicle brand of which the following models are classic cars:

  • 1925 Series 67
  • 1926-28 Series 69
  • 1930-31 Custom 8
  • 1932 Deluxe Custom 8
Abbreviation for Proton exchange membrane fuel cell
  1. Studs or nipples which may be used for alignment of parts or the placement of a part.
  2. Footpegs, often called pegs, are where the motorcycle rider’s feet rest. Some motorcycles have floorboards instead of pegs. With pegs, the rider usually rests the balls of his feet on the peg, whereas a floorboard is large enough to accommodate the whole foot.
A vehicle brand of which all models from 1951-58 are milestone cars.
PE headlight
A headlight with a gas discharge lamp and a polyellipsoidal reflector
Also spelled peen

  1. To flatten out the end of a Rivet, etc., by pounding with the round end of a hammer.
  2. The ball-shaped, or narrow wedge-shaped end of a hammer head opposite the flattened striking face
Pein hammer
Also spelled peen hammer. A body hammer with a pein of triangular section with a fairly sharply shaped end. Compare Ball pein hammer
The flattening or shaping with a pein hammer
Pellet catalyst
Pellet-type catalytic converter
The first type of automotive catalytic converter, introduced in the USA in 1975. It consisted basically of a sheet steel catalyst container surrounded by thermal insulation and a sheet steel outer shell. The catalyst container was fitted with one or two beds of ceramic pebbles (pellets) coated with a catalyst. This type of catalytic converter suffered from poor service life due to vibration-induced attrition of the catalytic coating; this also produced additional particulate emissions and the pellet bed caused high exhaust back pressure, resulting in poor engine performance. Pellet-type catalytic converters have been superseded by monolithic converters
Peltier effect
When direct current is passed through two adjacent metals, one junction will become cooler and the other will become warmer. This principle is the basis of thermoelectric refrigeration.
Abbreviation for Proton exchange membrane
Abbreviation for Proton exchange membrane fuel cell
Pencil-type glow plug
Pencil-type injector
An early GM injection nozzle
Pendulum impact test
The standard test methods are the Izod and Charpy tests; the specimens have a standard notch machined in them, and the impact energy absorbed in breaking the specimen is recorded
Penetrating oil
A special oil with very thin Viscosity that is used to free rusted parts (esp. nuts and bolts) so that they can be removed.
The extent that the fusion goes into the base metal as measured from the surface of the base metal.
An early bicycle which had a large front wheel (which was both the driving wheel and the steering wheel) and a smaller rear wheel. Its name comes from two British coins — the large penny and the small farthing.
A closed-cup test for flash points of oil.
(C5H12) A low boiling paraffin hydrocarbon.
Pentanes plus
A mixture of hydrocarbons, mostly pentanes and heavier, extracted from natural gas. Includes Isopentane, natural gasoline, and plant condensate.
Pent crown piston
A piston design with a sloping, pent-roof shaped piston crown to improve the flow of the fuel/air mixture and to increase engine compression
A combustion chamber whose upper surface resembles a shallow peaked roof. Usually used with four valves per cylinder.
Pent-roof combustion chamber
A combustion chamber whose top is angled like a roof
Abbreviation for Pavement Excavation and Repair. Pavement patching.
A condition in which the fuel actually boils due to excess heat. Percolation prevents proper atomization of the fuel causing rough running.

Percussion welding
The type of resistance welding in which the heating comes from an arc produced by an electrical discharge and instantaneous pressure applied during or immediately following the heating.

Perfect scavenging
The scavenging parameter of two stroke engines. In an ideal scavenging process, the fresh mixture is considered to push the combustion products out of the cylinder without mixing or exchanging heat. This process continues until all burnt gases have been expelled and the cylinder is completely filled with a fresh mixture
(PFCs) A group of man-made chemicals composed of one or two carbon atoms and four to six fluorine atoms, containing no chlorine. PFCs have no commercial uses and are emitted as a byproduct of aluminum smelting and semiconductor manufacturing. PFCs have very high 100-year Global Warming Potentials and are very long-lived in the atmosphere.
A compound (CF4) emitted as a byproduct of aluminum smelting.
  1. The general way a vehicle, machine, or material is able to accomplish its purpose.
  2. The ability of a vehicle to accelerate and reach top speed.
Performance characteristics of materials
The specific values for materials, obtained by standard test methods and available for the selection of appropriate materials
Performance handling system
A suspension system that can be improved by adding appropriate front and rear anti-roll bars, nitrogen-filled gas shock absorbers, and special springs
Performance ratings
Performance test
Performance tester
Performance tuning
The act of improving a vehicle’s performance in general or engine performance in particular, such as upgraded suspension, higher engine output and/or torque, or drag-reducing measures, such as the addition of spoilers
Perimeter frame
Sometimes called a Space Frame. A steel frame making up the chassis of a vehicle. The engine, transmission, body panels, and interior are all attached to the frame. Most cars today do not use a frame but are instead made with unibody construction.
Perimeter hot gas tube system
System that has a tube located on the surface of the outer portion of the cabinet to prevent condensation from forming.
Period of roll
The time occupied in performing one complete roll of a ship as from starboard to port and back to starboard
The outside edge or circumference.
Peristaltic pump
A type of positive displacement pump.
Permanent four-wheel drive
A British term for Full-time four-wheel drive. A permanently engaged four-wheel drive (with lockable or limited-slip differentials).
Permanent magnet
  1. The permanent magnet does not need electricity to function and will retain its magnetism over a period of years.
  2. Material which has its molecules aligned and has its own magnetic field; bar of metal which has been permanently magnetized.
The ease with which fluid flows through a porous medium.

Perpetual motion
A situation where a device will turn forever because there is no friction between the moving part and the stationary part. Although friction can be greatly reduced, it can never be eliminated. Thus a perpetual motion machine is impossible.
Perpetual motion machine
A device which will turn forever because there is no friction between the moving part and the stationary part. Although friction can be greatly reduced, it can never be eliminated.
Personalized license
A license plate chosen (at a cost) by a vehicle’s owner, rather than one allocated by the agency giving out the license. The letters and numbers may spell out a person’s name or occupation or even some cryptic reference. Also called vanity plate.
Personal license
A license plate chosen (at a cost) by a vehicle’s owner, rather than one allocated by the agency giving out the license. The letters and numbers may spell out a person’s name or occupation or even some cryptic reference.
Person trip
A trip by one or more persons in any mode of transportation. Each person is considered as making one person trip. For example, four people traveling together in one auto make four person trips.
A small valve or tap which is used to control the flow of liquid. You may find one at the bottom of a radiator to permit draining the radiator. A petcock may also be found on the line coming from the fuel tank in small engines and motorcycles. It allows you to cut the flow of gasoline going to the carburetor. On some motorcycles, the position of the petcock lever may permit draining the last part of the fuel tank as a reserve position. In units where the carburetor is fed by gravity feed from a fuel tank, turning off the petcock when the unit is not in operation may prevent gasoline from leaking past the carburetor’s Needle and seat and into the crankcase to dilute the oil.

An intermediate chemical derived from petroleum, hydrocarbon liquids or natural gas, such as: Ethylene, Propylene, Benzene, Toluene, and Xylene. Also includes organic chemicals, cyclic intermediates, plastics and resins, synthetic fibers, elastomers, organic dyes, organic pigments, detergents, surface active agents, carbon black, and ammonia.
Petrochemical feedstock
Chemical feedstocks derived from petroleum principally for the manufacture of chemicals, synthetic rubber, and a variety of plastics.
Petroil lubrication
A lubrication method for two-stroke engines where the oil is added to the fuel and lubricates the moving engine parts as the air/fuel mixture passes through the crankcase
A British term for gasoline.

  1. Raw material from which gasoline, Kerosene, lubricating oils, Propane, diesel fuel, etc. are refined. Consists primarily of hydrogen and carbon; but also contains other elements. Its source is decomposed organic matter which has been buried. Some used to think that the action of ice ages moved soil over great forests of tropical vegetation. The current suggestion is that great bodies of water flooded tropical vegetation in a cataclysmic event.
  2. A broadly defined class of liquid hydrocarbon mixtures including crude oil, natural gas liquids, natural gas, lease condensate, unfinished oils, refined products obtained from the processing of crude oil, and natural gas plant liquids. Volumes of finished petroleum products include nonhydrocarbon compounds, such as additives and detergents, after they have been blended into the products.
Petroleum Administration for Defense District
(PADD) A geographic aggregation of the 50 States and the District of Columbia into five Districts, with PADD I further split into three subdistricts. The PADDs include the States listed below:
Petroleum Council
Petroleum Exporting Countries
Petroleum Fuel
gasoline and Diesel fuel
Petroleum Gallon
Petroleum Gas
Petroleum jelly
A whitish jelly-like substance obtained from petroleum, used as a lubricant and as a protection against corrosion. A semi-solid oily product produced from de-waxing lubricating oil basestocks.
Petroleum products
Petroleum products are obtained from the processing of crude oil (including lease condensate), natural gas, and other hydrocarbon compounds. Petroleum products include unfinished oils, liquefied petroleum gases, Pentanes plus, aviation gasoline, motor gasoline, naphtha-type jet fuel, kerosene-type jet fuel, Kerosene, distillate fuel oil, residual fuel oil, Petrochemical feedstocks, special naphthas, lubricants, waxes, petroleum coke, asphalt, road oil, Still gas, and miscellaneous products.

Petroleum Institute
Petroleum refinery
An installation that manufactures finished petroleum products from crude oil, unfinished oils, natural gas liquids, other hydrocarbons, and alcohol.
Petroleum Supply
A set of categories used to account for how crude oil and petroleum products are transferred, distributed, or placed into the supply stream. The categories include field production, refinery production, and imports. Net receipts are also included on a Petroleum Administration for Defense (PAD) District basis to account for shipments of crude oil and petroleum products across districts.
Petrol pump
A British term for Gas pump. A pump which dispenses gasoline at a gas station
Petrol station
A British term for a Gas station or service station
Petrol tanker
A British term for a Tanker truck — a specially equipped truck for transporting gasoline and other fuels
PeugeotClick image for books on

A vehicle brand of which the 1925-1948 models, with required application, are classic cars. Also includes 405 (1987-current) and 505 (1979-91)

Abbreviation for Purge Flow Sensor
Abbreviation for perfluorocarbons
Abbreviation for Pressure Feedback EGR Sensor
Abbreviation for Port fuel injection (GM)
Abbreviation for Powerglide automatic transmission.
Abbreviation for Programmed Fuel Injection Honda’s fuel injection system for the Accord, Civic, Civic CRX, and Prelude models
Abbreviation for Programmed ignition system
P grit numbers
A standard system of grit numbers applied to sandpapers to ensure identical properties in products made by different manufacturers
  1. Measurement of the free hydrogen ion concentration in an aqueous solution. A pH of 7 is neutral. Acid substances have lower pH. Basic substances have higher pH.
  2. Mathematically, pH is the logarithm (base 10) of the reciprocal of the hydrogen ion concentration. The pH may range from 0 to 14, where 0 is most acidic, 14 most basic, and 7 is neutral. Natural waters usually have a pH between 6.5 and 8.5.
An open-type body with two cross seats, it usually accommodates five passengers. A folding windshield, folding weatherproof fabric top and removable side curtains are usually standard equipment. The four-seater was called a double phaeton, and the six-seater or seven-seater was called a triple phaeton.

  1. Distinct functional operation during a cycle.
  2. The space relationship of windings and changing values of the recurring cycles of AC
Phase Control
Phase displacement
The mechanical and electrical angle by which phases in a polyphase motor or main and capacitor (or starting) windings in an induction motor are displaced from one another
Phase Electrical
Phase-locked loop circuitry
Phase loss monitor
Motor protection device for polyphase motors that measures current flow to detect phase loss.
Phase pressure forming
Phase Separation
The phenomenon of a separation of a liquid or vapor into two or more physically distinct and mechanically separable portions or layers.
Phase Shift Keying
An organic compound that is an alcohol derivative of Benzene.
A wheel cylinder or caliper piston made of plastic (phenolic) material rather than metal.
Phenolic spacer
A carburetor base gasket made from a thermosetting resin used specifically for heat insulation between the carburetor and the intake manifold
The basis of symptoms
Term sometimes used to denote the sensing element on a thermostatic expansion valve.
Phillips head screw
A screw having a fairly deep cross slot instead of the single slot as used in conventional screws.
Phillips Recessed Head
A type of screw drive having a cross recess with a wide center opening, steep walls and a blunt conical bottom. Permits easy and rapid entrance of the 4-winged driver.
Phillips screw
A common type of cross-head screw
Phillips screwdriver
Phillips ScrewdriverPhillips Screwdriver Tip

A screwdriver with a blunted pointed tip that is shaped to fit the crossed slots in the heads of Phillips screws. It is distinguished from a Reed and Prince screwdriver which has a pointed tip.

Phosphate coating
A special conversion coating produced by phosphating. It is applied to camshafts which promotes oil retention.

Phosphate section
A section in a painting line in which Phosphate treatment is performed
Phosphate treatment
A treatment of metals with a phosphating solution to produce a phosphate conversion coating on the surface
Phosphating solution
A solution of phosphoric acid, often enriched with zinc, used during the bodywork production process for cleaning and rust prevention
Bearing material composed of tin, Lead, and copper.
Phosphoric acid fuel cell
(PAFC) A type of fuel cell in which the electrolyte consists of concentrated phosphoric acid (H3PO4) and protons (H+) are transported from the anode to the cathode. The operating temperature range is generally 160220°C.
A non-metallic substance that lowers the rate of oxidation, thereby helping resist corrosion.
Relates to branch of chemistry where radiant energy (sunlight) produces various chemical changes.
A light-emitting or light-sensitive diode commonly used in sensing or switching circuits.
Physical action wherein an electrical flow is generated by light waves.
Particle of electromagnetic energy found in solar radiation.
Method by which the molecular formation of an element changes due to light.
The manufacture by plants of carbohydrates and oxygen from carbon dioxide and water in the presence of chlorophyll, with sunlight as the energy source. Carbon is sequestered and oxygen and water vapor are released in the process. While plants can handle carbon dioxide in a beneficial way, they cannot process carbon monoxide as emitted from vehicle exhausts.
Photovoltaic cell
(PVC) An electronic device consisting of layers of semiconductor materials fabricated to form a junction (adjacent layers of materials with different electronic characteristics) and electrical contacts and being capable of converting incident light directly into electricity (direct current).

Photovoltaic module
An integrated assembly of interconnected photovoltaic cells designed to deliver a selected level of working voltage and current at its output terminals, packaged for protection against environmental degradation, and suited for incorporation in photovoltaic power systems.
PH value
A measure of the concentration of hydrogen ions in a solution, which shows the strength of acid or alkaline. The pH value of an aqueous solution is a number describing its acidity or alkalinity. The pH of a neutral solution is 7.0 at 25°C
Physical Properties
The characteristics of a substance which distinguishes it from another substance, such as color, density, electrical conductivity, magnetism, co-efficient of thermal expansion, etc.
Abbreviation for Product Information Bulletin. General information on a product.
Pick and finishing hammer
Pick and finishing hammerPick and finishing hammer

A widely used type of body hammer with a pointed end on one side and a shallow domed end for finishing on the other side

Picker set
Pick hammer
A hammer with a round head for conventional planishing and a small pick-shaped head for working away in sharp or tight corners. It should not be confused with a Bullet-point pick hammer, which has a more blunt pick, nor with a Pein hammer
Pickle park
Trucker slang for a rest area as in ‘I don’t often park overnight in the pickle parks.’
Pickle park pinger
Trucker slang for a CB with a roger-beep as in ‘I don’t care much for them pickle park pingers.’
The removal of oxide or mill scale from the surface of a metal by immersion, usually in an acidic or alkaline solution
Pickling attack
The initial chemical reaction between phosphating solutions and metal surfaces in phosphate treatment
Trucker slang for pick-up truck, light truck as in ‘Watch out for that pickum-up truck broke down in the right lane.’
  1. A utility truck with a closed cab and an open box. In Australia it is called a utility or ute.
  2. The transfer of material, as between bearing and shaft, caused by friction and heat due to lack of oil; can lead to seizure.
  3. A Pick-up coil
  4. A yoke — a triangular metal piece used to connect the main brake cable with the stirrup cable in a bicycle’s centerpull brake system
  1. A utility truck with a closed cab and an open box. In Australia it is called a utility or ‘ute.’
  2. The transfer of material, as between bearing and shaft, caused by friction and heat due to lack of oil; can lead to seizure.
  3. A Pick-up coil or yoke.
Pick-up assembly
Pickup camper
Pickup coil
Pick-up coil
The coil in which voltage is induced in an Electronic ignition. Inputs signal to the electronic control unit to open the primary circuit. Consists of a fine wire coil mounted around a permanent magnet. As the reluctor’s ferrous tooth passes through the magnetic field, an alternating current is produced, signaling the electronic control unit. Can operate on the principle of metal detecting, magnetic induction, or Hall Effect. It is also referred to as a stator or sensor.
Pick-up ignition
Pick-up ignition system
Pick-up module
A trigger-activated device which sends a signal to the ignition unit of an electronic ignition system
Pick-up pipe
Pick-up screen
Pick-up tool
A tool with a flexible or rigid shaft and a claw type pick-up end; used to retrieve small objects from hard-to-reach areas.

Pickup Truck
Picture machine
Trucker slang for a radar as in ‘Watch out for the picture machine at the corner of 9th and Wilcox.’
Picture taker
Trucker slang for police with radar as in ‘There’s a picture taker at the 27 mile marker.’
Abbreviation for Parameter Identification Location
Abbreviation for Parameter Identification Supported
Pien hammer
A vehicle brand of which the following models are classic cars:

  • 1921 Series 32
  • 1922 and up Series 33
  • All models from 1925
Pierced steel planking

(PSP) A sheet of steel about 30cm wide and about one metre long with a series of holes and ridges. When placed under the driving wheels of a vehicle that is stuck in sand or snow, it helps to give traction.

  1. Property of quartz crystal that causes it to vibrate when a high frequency (500 kHz or higher) voltage is applied. Concept is used to atomize water in a humidifier.
  2. Having the ability to generate a voltage when mechanical stress is applied, as in a piezoelectric crystal.
Piezoelectric ignition
A system of Ignition that employs the use of a small section of Ceramic-like material. When this material is compressed, even a very tiny amount it emits a high voltage that will fire the plugs this system does not need a Coil, points or condenser.
  1. A semitrailer built with reinforcements to withstand transport by a railroad
  2. The way empty log trailers are carried on the bed of a tractor such that no axles touch the ground. Also may refer to other kinds of vehicles carried on the rear of a power unit in a manner that axles do touch the road.
Piggyback cargo
Truck carrying motor vehicles piggyback-style on a power unit. The trucks being carried have their front axles off the ground resting on the vehicle in front. Several vehicles may be hitched together in this way. This category is also used for wreckers towing a vehicle. Piggyback also refers to the way empty log trailers are carried on the bed of a tractor such that no axles touch the ground. Also may refer to other kinds of vehicles carried on the rear of a power unit in a manner that axles do touch the road.
Pig iron
Produced in blast furnaces, pig iron is the raw material for practically all iron and steel products; contains about 3-5 percent carbon

Finely ground powders in the paint that give it its color.
A cable used to transmit electrical power from the tractor to the trailer. So named because it is coiled like a pig’s tail.

A broad highway designed for high-speed traffic

This is a steel or concrete bar which is driven into the ground to form part of the foundations for a building.

Pile caps
The structure built on top of piling to support the bridge beams.
Pile Voltage Transformer
  1. The build-up of metal on a contact breaker point. The opposite is Pitting
  2. A heavy beam of timber, concrete, or steel driven into the earth as a foundation or support for a structure.
A jet in the fuel-return line which establishes the mixture
A shaft or upright member or support holding up the roof. Also called a Post. The A-post holds up the windshield. The B-post is behind the front door about in the middle of the side of the roof. The C-post holds up the rear window. In station wagons, another post is placed between the B-post and the last post so that it becomes the C-post and the last post is the D-post.

Pillared hardtop
Pillar jack
Pillar light
A courtesy light mounted on the central pillar within the passenger compartment
Pillar reinforcement
Pillar switch
Pillion pad
A backrest pad which is mounted behind the seat on a motorcycle.
  1. A small fuel flame used to ignite the fuel at the main burner.
  2. When you want to drill a large hole into a piece of metal, the drill will have difficulty making the cut properly. So if you drill a small hole first, the larger hole will be easier to make. The small hole is a pilot hole or a pilot bore.
  3. If you are mating two pieces of metal (like the cylinder head to the cylinder) with a gasket in between, it can be difficult to line things up properly. So a temporary rod or stud is inserted to make it easier. Once it is lined up, the rod or stud is removed. The rod or stud is a pilot.
  4. A person who operates an airplane.
Pilot bore

Pilot bearing
A small bearing in the center of the flywheel end of the crankshaft, which carries the forward end of the clutch shaft. The British term is spigot bearing.

Pilot car
A car specifically marked to lead traffic through a construction or work zone.
Pilot circuit
Secondary circuit used to control a main circuit or a device in the main circuit.
Pilot hole
When using a large drill bit, it is sometimes hard for the drill to cut through the metal and do it evenly in a straight line. A pilot hole is first made with a small bit. Then, when you use the large bit, the drilling is much easier.
Pilot house
The enclosed space on the navigating bridge from which a ship is controlled when under way.
Pilot jet
A jet in the idling circuit of a fixed jet carburetor which measures and admits fuel
Pilot operated absolute
Pilot operated absolute valve
(POA) A suction throttling device used on some GM and Ford air conditioner system.
Pilot point
Similar to a ‘B’ point, a pilot point is a small (perhaps 1/8′ to 1/4′) unthreaded blunt portion at the end of a sheet metal or drive screw.
Pilot Program
Pilot shaft
A dummy shaft that is placed in a mechanism as a means of aligning the parts. It is then removed and the regular shaft installed.
Pilot valve
A small valve used to control action of a larger valve
A small cylinder used for fastening something or as a pivot.

Pin boss
Pinch-off pliers
Pinch Point
  1. A sharp conical point, usually of 45 degrees included angle, formed by a pinching operation.
  2. Traffic calming measure where sections of the road are narrowed to reduce speed
Pin circlip
Pin Clip
Pin Cotter
Pin end

A metallic rattling sound produced by the engine during heavy acceleration when the ignition timing is too far advanced for the grade of fuel being burned. The noise is caused by vibrations in the cylinder walls, head, and piston. When an engine pings, the normal, controlled even spread of the Flame front is disrupted by the spontaneous combustion of pockets of fuel. Their collision sets off the pressure waves that result in the pinging sound. Pinging can be caused by bad timing, inadequate octane rating, incorrect fuel-air mixture, a Hot spot in the combustion chamber caused by a glowing piece of carbon, or an overheat condition. Also called knocking.

Tiny bubbles in the paint finish that are often grouped together. It is caused by trapped solvents, moisture or air released from the film. Compare Solvent pop
A small, tapered gear which meshes with a larger gear or rack. It is found in two primary places in an automobile the Differential pinion and the Rack and pinion steering.

Pinion carrier
That part of the rear axle assembly that supports and contains the Pinion gear shaft.
Pinion gear
Pinion gearPinion gear

The smaller of two meshing gears. A pinion gear is used in a starter motor to engage the Flywheel ring gear and also rides along the surface of the Steering rack (a rod with grooves cut in it to mesh with the gear)

Pinion gearbox
Pinion shaft
Pinion shaftPinion shaft

A short drive shaft in the rear axle connecting the prop shaft to the crown wheel via the final drive pinion

Pinion steering
A British term for pinging
Pin kit
Pin lock
Pin lockPin lock

A pin with a hole at one end through which a Hair pin cotter is thrust to secure it in place.

Pinned piston ring
A steel pin, set into the piston, is placed in the space between the ends of the ring. The ring is thus kept from moving around in the groove.
Pinned ring
A steel pin, set into the piston, is placed in the space between the ends of the ring. The ring is thus kept from moving around in the groove.
Procedure for repairing cracks in the combustion chamber using threaded pins
Pin punch
A tool with a parallel shaft for use with a hammer to drive out pins, shafts, rivets, etc. Compare Drift punch
Pin slider caliper disc brake
A disc brake design with a sliding caliper. The major components are caliper (a casting with one cylinder and piston), caliper frame (casting), guide pins, Teflon or rubber sleeves/bushings. The caliper floats on the sleeves over the guide pins. The guide pins are threaded or riveted to the caliper frame. The caliper frame is bolted to the suspension
Pin spanner
A wrench with pins on forked ends, used to turn an Adjustable cup on a bottom bracket of a bicycle.
Pin Spring And Retainer
A thin, precisely contoured lines along certain body features; they may extend along the whole car and finish off in elaborate, bouquet-like designs. Striping usually refers to simple decorative lines, e.g., on motorcycle tanks, while pinstriping mostly refers to custom work, i.e., more elaborate and sharply curved lines
A thin, precisely contoured lines along certain body features; they may extend along the whole car and finish off in elaborate, bouquet-like designs. Striping usually refers to simple decorative lines, e.g., on motorcycle tanks, while pinstriping mostly refers to custom work, i.e., more elaborate and sharply curved lines
Pinstriping tool
A painting tool used to apply thin, precise lines on the body, e.g., on motorcycle tanks and to enhance car body contours.
Pintaux nozzle
A pintle-type diesel fuel injector nozzle with a hole in the side through which a very small amount of fuel is sprayed when the needle valve is partly opened at low pressure, before the main hole comes into use
  1. The needle of the injection valve in a diesel fuel injector.
  2. A vertical bolt or pin in a towing bracket, to which the towbar is attached.
  3. The top of some types of valves
  4. The pins or bolts that hinge the rudder to the gudgeons on the rudder post or sternpost
Pintle Hook
A coupling device used in a double trailer, triple trailer, and truck-trailer combinations. It has a curved, fixed towing horn and an upper latch that opens to accept the drawbar eye of a trailer or dolly.
Pintle nozzle
An injector nozzle containing the Pintle
Pin wrench
A wrench with a pin that can be fitted into a hole in a nut to exert extra pressure
Pioneer roads
Temporary access ways used to facilitate construction equipment access when building permanent roads.
Abbreviation for Profile ignition pickup
A tube used to transfer liquid or gas. Rigid conduit of iron, steel, copper, brass, aluminum, or plastic.

Pipe Caps
A cap that threads onto a pipe (like a nut) to seal one end.
Pipe Fitting
Any form of connecting parts which join together pieces of pipe.
Pipe Gas Forced-air
Pipe Plug
A short piece of threaded pipe, slotted, square head or socket, used to close up one end of a pipe fitting
Pipe Thread
American Standard pipe threads are tapered 1 inch in 16, or 3/4 inch per foot. They are 60 degree threads, of National form with flat or rounded top and bottom.

A system of Pipes
Pipe wrench

An Adjustable wrench with serrated jaws. The most common type of pipe wrench is the so-called Stilison wrench. Also called a monkey wrench.

  1. A system of Pipes.
  2. A rubber or plastic strip inserted between two removable panels, i.e., between a bolt-on fender and the body, to cover up the joint and to prevent water getting in; with the piping inserted, only the round bead along the upper edge of the piping is visible
  3. A seam in upholstery where the edge of the material is folded over a cord
Pip mark
A little dot or indentation which indicates the top side of compression ring
Piquet, Nelson
A three-time, World Driving Champion from Brazil and is considered one of the all-time great Formula One drivers
pistonClick image to supersize

A round or cylindrical plug, which closed at one end and open at the other. It slides up and down in the cylinder. It is attached to the Connecting rod and when the fuel charge is fired, will transfer the force of the explosion to the Connecting rod then to the crankshaft.

Piston bore
The diameter of the hole in the cylinder block in which the piston moves back and forth between top dead center (TDC) and bottom dead center (BDC)
Piston boss
The built-up area around the Piston pin hole.


Piston Caliper
Piston charging pump
  1. The function of the piston of the two-stroke engine to pre-compress the fresh charge induced into the crankcase.
  2. A separate piston used in earlier two-stroke engine designs to provide a supercharging effect
Piston clearance
The distance between the piston and the cylinder wall.
Piston collapse
A reduction in the diameter of the Piston skirt caused by heat and constant impact stresses.

Piston compression ring
A ring which surrounds the piston and fits in a grove in the piston. It is designed to seal the burning fuel charge above the piston. Generally there are two compression rings per piston and they are located in the two top Ring grooves. They also help to transfer heat from the piston into the cylinder walls and subsequently to the Water jacket surrounding the cylinder.

Piston compressor
A compressor in an air-conditioning system with one or more pistons arranged in either an in-line, axial, radial, or V-configuration
Piston crown
Piston crownPiston crown

The very top of the piston. The piston crown transmits the pressure created during the ignition of the air/fuel mixture to the piston pin, then to the connecting rod, and from there to the crankshaft. The diameter of the piston crown is slightly smaller than the piston skirt. Also called Piston dome.

Piston-crown combustion chamber
Piston-crown Combustion ChamberClick image to supersize
Piston-crown Combustion Chamber

The volume in the cylinder above the piston on the compression stroke that is used in diesel truck engines and in some European gasoline automobile engines. The advantage in simply machining a flat surface on the cylinder head is offset by the added cost of machining the bowl in each piston and by increased piston weight.

Piston damper
A small damper piston in an SU or Stromberg carburetor which reduces the movement of the large air piston in the venturi
Piston diaphragm
A flexible membrane which displaces under pressure, imparting movement to the piston in a Stromberg carburetor
Piston displacement
  1. Amount (volume) of air displaced by a piston when moved through the full length of its stroke.
  2. Sum of the volumes swept by an engine’s pistons as they travel up and down in their cylinders. Based upon bore (diameter of cylinder) and stroke (distance traveled by piston). Expressed in litres or cubic inches.
  3. Volume obtained by multiplying area of cylinder bore by length of piston stroke.
Piston dome
The top surface of a piston. It is often shaped for better combustion and to prevent a valve from contacting the surface.

Piston engine
A form of internal combustion engine. It is a heat engine in which the expansion of gas causes (by the explosion or a fuel and air mixture or the introduction of steam) a piston inside a cylinder to move and turn a crank shaft.
Piston expansion
Because pistons are usually made of aluminum and the cylinder walls are made of iron, the piston will expand more rapidly than the cylinder when they get hot. Some type of compensation needs to be made for this expansion or the piston will seize in the cylinder.

Piston extension screw
A stroke limiting screw between the primary piston and secondary piston stop
Piston head
That portion of the piston above the top ring.

Piston land
That portion of the piston which is between the Ring grooves.
Piston lands
That portion of the piston which is between the Ring grooves.
Piston lifter
A pin in the base of the piston chamber in an SU or Stromberg carburetor, used to check the strength of the mixture and the free movement of the piston
Piston material
The materials from which pistons are made are grey cast or light alloys; most light alloys consist of an aluminum-silicon alloy
Piston pin
Piston pinPiston pin

A steel pin that is passed through the piston, it is used as a base upon which to fasten the upper end of the Connecting rod. It is round and may be hollow. Also called wrist pin or gudgeon pin.

Piston pin boss
Piston pin circlip
A Circlip which is used on either end of the piston pin to hold the pin in place. Also called snap ring.
Piston pin end
The small end of the connecting rod through which the piston pin is inserted
Piston Pump
Piston ring
A metal, split ring installed in the groove on the outside wall of the piston. The ring contacts the sides of the Ring groove and also rubs against the cylinder wall thus sealing the space between the piston and the wall. Poor rings can cause poor compression and severe Blowby. Often seen as blue smoke out the exhaust pipe.

Piston ring, chrome
Piston ring clamp
A special automotive tool used for installing pistons. The clamp is slipped over the piston and when tightened, compresses the piston rings into the piston grooves. With the piston rings compressed, the piston can be installed into the cylinder by light tapping
Piston ring end gap
The distance left between the ends of the ring when installed in the cylinder.
Piston ring expander
A spring device placed under a piston ring to hold it snugly against the cylinder wall.


Piston ring flutter
The oscillations of a piston ring which mainly occur at high engine speed and thus can cause breakage
Piston ring gap
Piston ring groove
One of the channels into which the piston rings reside.
Piston ring groove cleaner
A special automotive tool to remove carbon and varnishes from piston grooves before installing piston rings
Piston ring job
Reconditioning the cylinder and installing new rings.
Piston ring, oil control
Piston ring, pinned
Piston ring pliers
A pliers-like special automotive tool used to spread and slip piston rings over a piston for removal and installation
Piston ring ridge
That portion of the cylinder above the top limit of ring travel. In a worn cylinder, this area is of a smaller diameter than the remainder of the cylinder and will leave a ledge or Ridge that must be removed.
Piston ring side clearance
The space between the sides of the ring and the ring Lands.
Piston ring stop
A pin pressed into the ring grooves of a two-stroke engine in order to prevent the rings from rotating, which would allow the open ends to become jammed in the ports
Piston rocking
Piston rod
A shock absorber rod which operates the piston in a telescopic damper
Piston seal
A fluid seal on a disc brake caliper piston
Piston seizure
A sudden stalling of the engine, caused by the piston becoming stuck in the bore; this is often caused by overheating or lack of lubrication and often leaves severe score marks in the cylinders and on the skirt of the piston.
Piston skirt
Piston skirtPiston skirt

The portion of the piston below the rings and Bosses. It absorbs the thrust caused by the crankshaft as it makes contact with the cylinder wall. (Some engines have an Oil ring in the skirt area, though not common.)

Piston skirt expander
A spring device placed inside the Piston skirt to produce an outward pressure which increases the diameter of the skirt.
Piston skirt expanding
Enlarging the diameter of the Piston skirt by inserting an Expander, by Knurling the outer skirt surface, or by Peening the inside of the piston.
Piston slap
The condition caused by too much Clearance between the piston and the cylinder walls. The piston rattles or slaps against the wall of the cylinder. It makes a hollow, muffled, bell-like sound. Also called piston rocking.
Piston speed
The speed of the piston for a given engine rpm
Piston spring
A coil spring in an SU carburetor which counteracts the upward movement of the piston
Piston stops
Tabs, or protrusions, on a backing plate positioned to prevent the wheel cylinder pistons from leaving the wheel cylinder.
Piston thrust
The pushing action of the piston which occurs at the sides of the piston 90° away from the piston pin as it pushes against the cylinder wall.
Piston Tool
Piston top
Piston-type compressor
A compressor in an air-conditioning system with one or more pistons arranged in either an in-line, axial, radial, or V-configuration
Piston-valve engine
A two-stroke engine that relies on the ports in the cylinder walls to control admission and exhaust of the air/fuel mixture; it is not equipped with other control elements such as rotary valves
  1. Area at a race track for fueling, tire changing, making mechanical repairs, etc.
  2. Small craters in the surface of metal.
  1. The back and forth rocking motion of a vehicle which compresses the front springs and extends the rear springs so that the nose of the vehicle is down while the tail is up. Then the action reverses so that the nose is up and the tail is down (i.e., dive and Squat).
  2. The distance between two adjacent threads on a bolt or screw measured at the outside diameter of the threads.
  3. The distance, measured parallel to its axis, between corresponding points on adjacent thread forms in the same axial plane and on the same side of the axis.
  4. The distance between a point on one gear tooth and the same point on the next gear tooth.
  5. The quality of sound with respect to the frequency of vibration of the sound waves.
  6. The angle at which something is tilted.
  7. In Britain, a parking space or site for a trailer, camper, etc.
Pitch circle
(PC) the circumference on which the centers of the wheel bolt holes are located
Pitch circle diameter
(PCD) The diameter of the stud holes/bolt holes for fixing the wheel to the hub. The pitch circle (PC) is usually shown as a double number, e.g., 5-5.5. The first number indicates the number of holes, and the second, the diameter of the PC
Pitch control
Pitch diameter
On a straight thread the diameter of the coaxial cylinder the surface of which would pass through the thread profiles at such points as to make the width of the groove equal to one-half of the basic pitch. Approximately half way between the major and minor diameters.
Pitch gauge
Pitch Line
A generator of the cylinder or cone of a screw thread specified in the definition of pitch diameter.
Pitch Pulley
Pitch stator
Pitman arm
A short lever arm Splined to the Steering gear Cross shaft, the pitman arm transmits the steering force from the Cross shaft to the Steering linkage system. In this way rotary motion of the steering wheel is turned to lateral movement of the arm. The British term is drop arm.


Pitman shaft
Pitot tube
A tube for measuring the pressure and velocity of a fluid flow; in some CVTs, used in conjunction with a valve arrangement to control ratio changes
Pit road
The paved roadway that leads into the pit area from the racetrack.
  1. Area at a race track for fueling, tire changing, making mechanical repairs, etc.
  2. Cavities extending from the surface into the metal as a result of pitting corrosion or rust.
Pit stop
  1. A stop at the pits by racer, for fuel, tires, repairs, etc.
  2. Colloquial term for going to the toilet.
Leather A high quality, natural, supple, and quick drying leather
Pittards leather
A high quality, natural, supple, and quick drying leather
Eroded Contact breaker points
Surface damage to a metal in the form of pits or holes. The opposite is Piling
Pitting corrosion
  1. A corrosion process resulting in Pits
  2. Deep corrosion in localized spots on an object–even stainless steel. Dirt or grease on certain portions of the object may block oxygen from that surface, thus impeding the passive film which protects stainless from corrosion.
Pitting factor
The ratio of the depth of the deepest pit to the average penetration as calculated from weight loss
Abbreviation for Peak Inverse Voltage
A pin or shaft about which a part moves. The place at which a lever swivels. A lever cannot work without a pivot.

Pivot axis
Pivot bolt
A bolt on which the arms of caliper brakes pivot and which also serves as the means for mounting the brakes on the bike frame. Also called Mounting bolt.
Pivot pin

Pivot ring
Pivot swing axle
Common abbreviation for pickup truck
Abbreviation for Passive Keyless Entry
Abbreviation for Parking lock
Abbreviation for Public Liability and Property Damage as a form of basic Car insurance
Place in service
A vehicle is placed in service if that vehicle is new to the fleet and has not previously been in service for the fleet. These vehicles can be acquired as additional vehicles (increases the size of the company fleet), or as replacement vehicles to replace vehicles that are being retired from service (does not increase the size of the company fleet).
Plain bearing
A cylindrical sleeve friction bearing; most commonly used type of bearing.

Plain carbon steel
Plain disc wheel
A type of wheel without holes or slots in the wheel disc
Plain gage tubing
Plain gauge tubing
Tubing whose thickness remains constant over its entire length.
Plain Sheared Point
The end of a metal object cut approximately flat and square to the axis, without chamfer.
Plain wrapper
Trucker slang for an unmarked police car as in ‘Plain wrapper sitting at the 57 taking pictures.’
Planar cells
A flat surface.

Planer Head Bolt
A bolt having a large, low square head, designed for insertion in T-slots of planer, shaper, or milling machine tables.
Plane sailing
A method of navigation which ignores the earth’s curvature, treating its surface as a plane. Colloquially it indicates travel or procedure without difficulty or obstruction.
Planetary albedo
The fraction of incident solar radiation that is reflected by the Earth-atmosphere system and returned to space, mostly by backscatter from clouds in the atmosphere.
Planetary gear
A gear used in some starters as an intermediate transmission

Planetary gear differential
A planetary gear set used as a differential with asymmetric torque distribution, as used in 4WD vehicles
Planetary gears
Planetary gearset
  1. A Gearing unit consisting of a Ring gear with internal teeth, a sun or central Pinion gear with external teeth, and a series of Planet gears that mesh with both the ring and the Sun gear. Frequently used in Overdrives and automatic transmission. Also called Epicyclic gearbox.
  2. A central externally toothed sun gear, an internally toothed outer ring gear, and several intermediate planet gears which are evenly spaced and supported by a planet carrier; they are in constant mesh with the sun gear and the internal gear
Planetary gear set
Planetary-gear system
A gearset used in automatic transmissions that features a central gear, called a sun gear, surrounded by two or more smaller planetary gears that mesh with a ring gear.
Planetary set
Planetary transmission
A form of gear used by Benz in which small Pinions revolve around a central or Sun gear and mesh with an outer Ring gear called the annulus. Type used in the Ford Model T. Also called Epicyclic gearbox and ‘sun-and-planet gears’.
Planet carrier
That part of a Planetary gearset upon which the Planet gears are affixed. The planet gears are free to turn on hardened pins set into the carrier. The planet carrier revolves around the central axis of a planetary gear set and supports the planet gears
Planet gear
Planet gears
Those gears in a Planetary gearset that are in mesh with both the ring and the Sun gear. They are referred to as planet gears in that they orbit or move around the central or Sun gear.

Planet pinion
Planet spider
A common type of Planet carrier with a Spider or web-style design
Planet wheel
The final panel hammering stage for lifting out minor imperfections in a panel surface. Part of the panel finishing process
Planishing hammer
Planishing hammerPlanishing hammer

A specialized hammer used in repairing damaged body work

Planck’s constant
Constant value (6.626 x 10-34 watt seconds squared) which, when multiplied by the frequency of radiation, determines the amount of energy in a photon.
Plan lines
The plans that show the shape or form of the ship
Planned obsolescence
A policy of manufacturers that encourages motorists to become dissatisfied with their cars so that they are eager to buy the latest model.
Plant condensate
One of the natural gas liquids, mostly Pentanes and heavier hydrocarbons, recovered and separated as liquids at gas inlet separators or scrubbers in processing plants.
Plant Liquids
Plant products
Natural gas liquids recovered from natural gas processing plants (and in some cases from field facilities), including ethane, Propane, Butane, butane-propane mixtures, natural gasoline, plant condensate, and lease condensate.
Temporary physical condition of a gas after it has been exposed to and has reacted to an electric arc.
Plasma arc cutters
Cutting equipment that makes clean, fast cuts without destroying the properties of high-strength steels
Plasma coating
A process which deposits a hard, long-wearing surface on piston rings.
Plasma spray process
The process in which a very high temperature flame is produced by blowing gas through an electric arc. Metal wire or powder is melted by passage through the flame and is projected on the surface to be coated
A material that contains as an essential ingredient one or more organic polymeric substances of large molecular weight. It is solid in its finished state and, at some stage in its manufacture or processing into finished articles, can be shaped by flow.

Plastic deformation
A permanent change in the shape or size of a solid body without fracture resulting from the application of sustained stress beyond the elastic limit
Plastic engine
An automobile engine whose bulk is made of plastic components (e.g., engine block, inlet manifold, water-pump housing, valve covers, oil pan), the use of metal being limited to parts subjected to extreme mechanical or thermal loads (e.g., combustion chamber, exhaust manifold, pistons, cylinder liners, valve train, etc.)
Plastic filler
  1. To soften a material to make it plastic or moldable by heating, kneading, or adding a plasticizer
  2. To soften an adhesive, coating or sealer, generally by the addition of high boiling liquids or plasticizers
  1. An additive that gives flexibility to an otherwise rigid plastic
  2. A liquid or solid chemical added to a compound to impart softness or flexibility. Some plasticizers have an undesirable tendency to migrate from the parent material into nearby surfaces which are receptive. When they migrate into adhesive films, for instance, they generally cause loss of strength or complete failure of the bond
Plastic molding
A process that converts organic-based materials, by means of a general-purpose press and purpose-built Tooling under controlled heat and pressure, and injects the hot material into a die cavity shaped in the final form of the intended part.
Plastics welding
A uniting of thermoplastic, i.e., non-setting plastics of similar or different type using heat and pressure and with or without the addition of plastic of a similar kind (filler material). The welding proceeds within the temperature range of thermoplasticity of the contact surfaces on the parts to be welded; the freely mobile molecular chains in the marginal areas flow together and become interlaced
A soft plastic that flattens out to predetermined widths when subjected to torque; these widths equal a specific clearance. It is normally used to check main and rod-bearing clearance. It is sold in a paper sleeve that also doubles as the scale on which it is measured (in thousandths of an inch)
A plastic material that compresses to the thickness of the clearance between a crankshaft journal and a bearing when the bearing retaining cap is installed, so the clearance can be checked against specifications
  1. The action of Coating a material with some metal. Also called Electroplate or Anodize.
  2. A flat piece of material often used to mount another device.
  3. Two lead-alloy plates in each cell of a battery where the positive plate is made of lead peroxide and the negative plate is made of spongy lead. The plates are arranged in groups, in an alternate fashion, called elements. Separators are placed between the plates of different polarity. Plates and separators are completely submerged in the electrolyte.
  4. The electrode, in a valve or tube, held at a positive potential with respect to a cathode, and through which positive current generally enters the vacuum or plasma, through collection of electrons.
  5. Clutch discs
  6. The electro-chemical coating of a metal piece with a very different metal.
Plate frame
Plate grid

Plate group
An assembly of plates of identical polarity (positive or negative) used in a battery cell
Plate keel
Plate lamp
Plate light
Plate strap
The conducting connection between the lugs of battery plates of like polarity and the cell terminal
Plate support
The support at the bottom of a battery case on which the elements rest. It provides space for the sediment chamber
Plate-swash Plate
Primary load-bearing structural assembly of a motor vehicle determining the basic size of the motor vehicle, and is the structural base that supports the driveline and links the suspension components of the motor vehicle.

Platform Bus
Platform frame
The underbody construction consisting of a reinforced and fairly flat section that forms the entire lower portion of a vehicle. It includes the floorpans and is bolted to the body; (e.g., Volkswagen Beetle)
Platform pedal
Older style pedal that the foot rests on top of and is not locked into.
Platform take-up point
Platform Trailer
A flatbed trailer. There are straight platforms, single drops, and double drops.
The coating of metal usually by electrolysis.

A precious light-grey, heavy, ductile, noble metal, atomic number 78, atomic weight 195.09; melting point at 1769°C. It is the main member of the so-called platinum metals. Together with other platinum metals, it is used as a catalyst in automotive exhaust converters. It is used in the construction of breaker points. It conducts electricity well and is highly resistant to burning.
Platinum electrode
A spark plug electrode made of platinum which lasts longer than one of nickel alloy because it can better withstand high temperatures
Platinum metals
A generic term for a family of noble metals found with and resembling platinum. It includes ruthenium, rhodium, palladium, osmium, iridium, and platinum. They are used as catalysts in catalytic converters. Less than a tenth of a troy ounce is required per converter to produce acres of catalytically active catalyst surface
Platinum spark plug
A spark plug with a platinum center electrode
Platinum-tipped spark plugs
Most General Motors vehicles built since 1995 are equipped with platinum-tipped spark plugs. Under normal operating condition, platinum-tipped spark plugs are designed to function up to 166,000 km. They are designed to operated with a wider gap. The electrode is platinum-tipped and the body is stainless steel.
Movement between two parts.

  1. A chamber, located between the throttle body and the runners of an intake manifold, used to distribute the intake charge evenly and to enhance engine breathing.
  2. An enclosure containing air or gas at a higher pressure than exists outside.
  3. The air ducts, air valves and blower assembly inside the instrument panel
Plenum chamber
  1. A large cast alloy body in an induction system which connects the throttle body or inlet tube to the cylinder head(s) or inlet manifold.
  2. The air compartment in a car body formed between the scuttle and the bulkhead, providing a basis for the interior air supply
  3. Chamber or container for moving air or other gas under a slight positive pressure.
A trade name for an Acrylic plastic, made by theRhom and Haas Co.

A gripping tool with two hinged arms and serrated jaws.

PLL circuitry
A phase-locked loop circuitry in a radio which locks the station frequencies to ensure utmost frequency stability
Plow bolt
Plow boltPlow bolt

A bolt with a countersunk, flat head, square neck, and unified thread pitch. Used in road graders, scoop shovels and other heavy-duty equipment where a smooth surface is required at the spot of head protrusion

Plowing snow
Using mechanical means to push or clear snow away from the road surface
  1. A removable cork or stopper which fills a hole.
  2. A spark plug.
  3. A male electrical connector.
  4. To seal with a stopper
Plug boot
Plug boot puller
Plug brush
Plug cable
Plug cable cover strip
Plug cable loom
Plug cable marker
Plug cable separator
Plug caddy
A special box which can hold spare spark plugs and is especially used by snowmobilers.
Plug cap
The device on the end of the high tension wire coming from the coil and mounted on the spark plug. Also called Spark plug cap
Plug condition
Plug electrode
Plug gap
Plug gapping
Adjusting the side electrode on a spark plug to provide the proper Air gap between it and the center electrode.
Plug gauge
Plug Heat Range
Plug ignition
Plug-in diagnosis
On-board computer provides means for special test equipment to be plugged in for making a series of programmed tests to check condition of various units and systems on the vehicle
Plug indicator
Plug insert tap
Plug insulator
The hole in a tank or cistern, which can be closed with a rubber plug
Plug key
Plug lead
Plug patch
A tire repair material which is forced into a nail hole to fill it. The plug is attached at one end to a patch that seals the hole and then expands to fill the hole. Although a common procedure, it is not the most satisfactory method of repair
Plug pliers
Plug repair
The filling of a nail hole by forcing repair material into the damaged area, often while the tire is mounted and containing air. It is not a satisfactory method of repair.
Plug reversal
The reconnecting of an electric motor’s windings to reverse its direction of rotation while running
Plug shell
Plug socket
Plug spanner
Plug starter switch
Plug tap
Tapping threads in a blind hole
Plug tester
Plug Valve
Plug weld
A weld which holds two pieces of metal together and made in a hole in one of metal which is lapped over the other pieces. Also called rosette weld.
Plug welding
A number of holes are punched along the edge of the repair section to be welded in; the section overlaps the damaged area to be repaired and is welded to the base metal at the punched boles. This is a convenient way of duplicating the spot welding process used by manufacturers, as spot welding equipment is usually too expensive and cumbersome for repair purposes
Plug whiskering
Plug wire
Plug wire cover strip
Plug wire loom
Plug wire marker
Plug wire separator
Plug wrench
  1. Any immersing type of piston.
  2. A hydraulic tappet component (e.g., in a valve).
  3. An actuating element in an ignition lock.
  4. A piston in a starter solenoid.
Plunger principle
A new ABS control system which offers improved pressure modulation with very small amplitudes even at pressures close to zero. Compare Valve principle
Plunger pump
An oil pump consisting of a reciprocating plunger in a ported chamber
Plunger suspension
A suspension system in which the vertical movement of the axle is controlled by springs mounted above and below the axle.
Plunging joint
A Slip joint which is a connection in the drive train, of variable length, which permits the drive shaft to change in effective length. The British term is ‘sliding joint’
A layer of rubber-coated parallel cords which forms a unit of a tire carcass. The plies are made of cord, fiberglass, steel, or structural fabric.

PlymouthClick image for books on

A vehicle brand of Chrysler of which the Fury for 1956-58 are Milestone cars. The Satellite SS and GTX for 1965-70 are milestone cars. The Barracuda Formula S for 1965-69 are milestone cars. The Roadrunner and Superbird for 1968-70 are milestone cars. Acclaim (1989-95), Breeze (1996-2000), Caravelle (1983-88), Colt (1971-94), Colt Vista (1988-94), Grand Voyager (1974-2000), Gran Fury (1975-77, 1980-89), Horizon (1978-90), Laser (1990-94), Neon (1995-2001), Prowler (1997-2000), Reliant (1981-89), Sundance (1987-94), and Voyager (1974-2000)

Ply rating
(PR) An indication of tire strength and load carrying capacity. It does not necessarily indicate actual number of plies. A two-ply four-ply rating tire would have the Load capacity of a four-ply tire of the same size but would have only two actual plies. This system of measurement has been replaced by the term Load range.
Ply separation
A breakdown of the bonding compounds resulting in the plies detaching from each other. Usually as a result of excessive heat.
Ply tire
Ply turnup
The extension of a carcass ply to its end after wrapping around the bead. Also called ‘flipper strip’
Abbreviation for Particulate matter
Abbreviation for Pump Mounted Driver
Abbreviation for Polymethyl methacrylate
PM trap
A diesel particulate filter
Abbreviation for Pulse-width modulated
Abbreviation for Part number
Abbreviation for Part number
Pneumatic device
A device moved or worked by air pressure.
Pneumatic suspension
Pneumatic tire
A flexible, hollow rubber forming the outer part of the vehicle wheel and inflated by air pressure. Originally rubber tires were solid core. Dunlop was the first to invent a tire with an air-filled tube for bicycles. Later, Tubeless tires were invented. The tire is filled with enough compressed air to support the weight of the vehicle and cushion road impacts. The opposite is Solid tire
Pneumatic trail
The distance between a vertical line through the center of the wheel and the center of pressure of the tire contact patch; most apparent during cornering.

The study of pressure and flow in gases. A pneumatic Drill is operated by compressed air; a Pneumatic tire contains compressed air.
Abbreviation for Partnership for a New Generation of Vehicles.
  1. Three element transistor made of two layers of semi-conductor materials
  2. Abbreviation for Park/Neutral Position switch which determines if the gear selector is in Park or Neutral
Abbreviation for Pilot operated absolute valve used in some air conditioning systems
POA suction throttling valve
A term standing for pilot operated absolute and is a modification of a suction throttling valve which has a metal bellows with a vacuum instead of a diaphragm; it provides more accurate evaporator pressure control, allowing for lower evaporator temperatures without cone icing
Pocket caliper
A small slide-type caliper for inside and outside measurement up to about 100 mm or 4 inches
Pocket Compressor
Pocket slide caliper
A small slide-type caliper for inside and outside measurement up to about 100 mm or 4 inches
A housing for a gauge mounted on the instrument panel.

Pod filter
A foam filter which is like a sock (open at one end and closed at the other) and is clamped on the horn of a carburetor
Abbreviation for Port of Entry
Point Depression
Point file
Point gap
The space between the Contact points when they are fully open. The distance of the gap will determine the effectiveness of the points.
Point gauge
Point injection
Two or more metal terminals, located inside the distributor on vehicles with non-electronic ignitions. These terminals are brought into contact and then separated by the movement of the cam wheel on the rotating distributor shaft. The points regulate the intensity and duration of the current that is conducted to each spark plug by interrupting the flow of current from the coil as they open and close. Also called Contact points, breaker points, or ignition points.

Points file
A thin, fine-toothed file for cleaning and smoothing off the piles on contact breaker points
Points gap
A gap between the contact breaker points when fully open; measured with a feeler gauge
Point steering
Point taker
See Coordinate measuring machine
Point Valve
A colloquial term for power or acceleration
  1. Indicates if the Pole shoes are so magnetized as to make current low in a direction compatible with the direction of flow as set by the battery.
  2. Indicates if the end of a magnet is the North or South pole (N or S).
  3. Indicates if the battery terminal (either one) is positive or negative (plus or minus) (+ or -).
  4. The terms (positive, negative, north, and south) that indicate the direction of current and flux flow in electrical and magnetic circuits at any given instant
Polarization curve
Typically a plot of fuel cell voltage as a function of current density (V vs. A/cm2 or similar units). The curve is obtained under standard conditions so that fuel cell performance can be compared between different cell designs, and may be obtained by either a single cell or a stack test.
Polarization resistance
The transition resistance between the electrodes and the electrolyte; part of the internal resistance of a battery. Compare Internal resistance
The process of sending a quick surge of current through the Field windings of the Generator in a direction that will cause the Pole shoes to assume the correct Polarity. This will insure that the generator will cause current to flow in the same direction as normal.
Polar moment of inertia
The resistance of an object to rotational acceleration. When the mass of an object is distributed far from its axis of rotation, the object is said to have a high polar moment of inertia. When the mass distribution is close to the axis of rotation, it has a low polar moment of inertia. A mid-engined car has most of its mass within its wheelbase, contributing to a low polar moment of inertia, which, in turn, improves cornering turn-in.

  1. One end, either North or South, of a magnet.
  2. A post or long shaft.
  3. The best starting position in an auto race. It is the inside space on the first row of drivers. Most races begin with the cars in a formation of rows of two. Most events begin with a standing start or a rolling start.
Pole Magnetic
Pole piece
A soft magnetic core of the inductive winding in a magnetic pick-up assembly; stator
Pole position
The best starting position in an auto race. It is the inside space on the first row of drivers. Most races begin with the cars in a formation of rows of two. Most events begin with a standing start or a rolling start.
Poles cargo
This cargo category includes processed wood, like 2×4’s, plywood, pulpwood, firewood, and new pallets, fresh from the factory, but not used empty crates. Wood chips, wood residuals, and bark are solids in bulk.
Pole shoe
Pole shoes
Metal pieces about which the Field coil windings are placed, when current passes through the windings, the pole shoes become powerful magnets, example Pole shoes in a Generator or starter motor.
Pole Trailers
A logging trailer. Usually has bunks for holding logs. The center portion of the trailer may be adjustable in order to accommodate loads of different lengths.
Pole Truck
  1. A winch truck with lifting equipment for lifting poles in oilfield service and contracting. It can have an A-frame.
  2. A flatbed truck with bunks.
  1. A substance like wax used to make the exterior paint shine or gloss.
  2. The act of making the paint shine.
  3. To make smooth or lustrous by friction with a very fine abrasive.
  4. To remove the minor obstructions in the exhaust flow. A term sometimes coupled with Porting, as in porting and polishing or port and polish. This is generally a process of Blueprinting a two-stroke engine so that the Intake and exhaust ports are polished and have no obstructions in the flow of fuel-air mixture or exhaust gases. In this way the engine generally has more performance. A problem may arise when an individual port has been polished too much.
Polishing barrel
A barrel used for a polishing process in which the aluminum surface is smoothed in the presence of metallic or ceramic shot by a rotating movement of the barrel
Hydrocarbons, carbon monoxide, and nitrogen oxides.

Pollutant Discharge Elimination System
National Pollutant Discharge Elimination System
The impairment (reduction) of water quality by agriculture, domestic, or industrial wastes (including thermal and radioactive wastes) to such a degree as to hinder any beneficial use of the water or render it offensive to the senses of sight, taste, or smell or when sufficient amounts of waste creates or poses a potential threat to human health or the environment.

(PC) A polyester polymer in which the repeating structural unit in the chain is of the carbonate type; used for bumpers, body and roof panels
Polychlorinated biphenyl
(PCB) Dielectric fluid used in capacitors and transformers that is very toxic. Use of PCB in transformers and capacitors is strictly regulated by the Environmental Protection Agency.
Polycyclic Organic Matter
(POM) A class of air toxics defined in the US Clean Air Act as compounds with more than one Benzene ring and a boiling point of 100°C and higher. Includes practically all of diesel PAH material.
A curve which is an ellipse in every direction so that the light of the bulb which is positioned at the focal point will bounce into the same forward direction.
Polyellipsoidal headlight
A headlight with a gas discharge lamp and a polyellipsoidal reflector
A synthetic fiber.
Polyester filler
A body repair material for smoothing dents in body panels; includes a resin base filler paste and a catalyst which is added to the base filler and hardens by chemical reaction
Polyester powder
A powder used for electrostatic powder coating
(PE) A polymer prepared by the polymerization of ethylene as the sole monomer; very resistant to chemical attack. High-density polyethylene (HDPE) is used, e.g., for blow-molded parts such as tanks for fuel, coolant, washer and brake fluid; Low-density polyethylene (LDPE) is used for plastic film and sheet

A paint finish used on some vehicles and was advertised to require no cleaning except for an occasional wash.


A material consisting of large units (molecules) made by joining many smaller building blocks (simple molecules). Usually used to describe synthetic rubber.
Polymer alloy
A mixture of two or more different compatible polymers
Polymer coating
A Coating that prevents paint from oxidizing and so protects a vehicle from premature fading and rusting. Professionally applied, it will last up to three years.
The bonding of two or more monomers (by chemical reaction) to produce a polymer. Plastic parts produced from specific polymer alloys usually give better performance in respect to thermal and mechanical properties as compared to those of parts consisting of the respective individual components
Polymethyl methacrylate
(PMMA) A thermoplastic polymer derived from methylacrylate; transparent solid with excellent optical qualities and weather resistance; typical automotive applications are the lenses of rear lights. Also called Perspex
Polynuclear Aromatic Hydrocarbons
(PAH); Aromatic hydrocarbons with two or more (up to five or six) Benzene rings joined in various, more or less clustered forms.
Polyphase motor
Electrical motor designed to be used with a three-or four-phase electrical circuit.
Polyphenylene oxide
(PPO) The characteristics of this plastic are high impact strength, good thermal and dimensional stability as well as excellent flame-resistance
Polypropylene (PP)
An extremely versatile plastic, available in many grades and also as a copolymer (ethylene/propylene). PP has the lowest density of all thermoplastics (900 kg per cubic metre) and is characterized by excellent strength, stiffness, fatigue, and chemical resistance. Also used in fabric because it is extremely hydrophobic, fast drying, does not absorb moisture, lightweight, strong, and abrasion resistant.
  1. A polymer of styrene that is a rigid, transparent thermoplastic with good physical and electrical insulating properties, used in molded products, foams, and sheet materials.
  2. Plastic used as an insulation in some refrigerated structures.
Synthetic rubber compounds used in adhesives, coatings and sealers. When cured, they are almost unaffected by aliphatic or aromatic solvents; and retain flexibility and shock resistance at low temperature. Flow characteristics, odor and high relative cost limit their use as adhesives to very specialized applications. High performance sealers of this base are widely used for aircraft and marine requirements
(PTFE) The major advantages of this material are its excellent chemical resistance and its extremely low coefficient of friction; automotive uses are parts where these characteristics are relevant, such as in valve stem seals, friction bearings, and joints
Polyurethane (PUR)
  1. A thermoplastic material with high strength, good chemical and abrasion resistance; used mainly for foamed reaction injection moldings and for adhesives, such as for flush-bonded body glass
  2. Any synthetic rubber polymers produced from the polymerization of an HO and NCO group from two different compounds. Often used in insulation and molded products.
Polyurethane blades
A plow blade composed of hard plastic that provides more flexible blade action over road obstructions than steel blades
Polyurethane paint
A type of two-pack paint based on polyurethane substances
Polyurethane powder
A powder used for electrostatic powder coating
A drive belt with multiple Vs; flat, similar to the toothed belts used as timing belts, but with lengthwise V-shaped ribs rather than transverse cogs; used increasingly on new engines instead of conventional V-belts
Polyvinyl chloride

  1. A polymer of vinyl chloride. Tasteless, odorless, insoluble in most organic solvents. A member of the family vinyl resin, used in soft flexible films for food packaging and in molded rigid products, such as pipes, fibers, upholstery, and bristles.
  2. Both plasticized and unplasticized PVC types are marked by good weathering resistance, excellent electrical insulation properties, and good surface properties; they are self-extinguishing
Abbreviation for Polycyclic Organic Matter
Pony Axle
Colloquial term for a smaller diameter wheel attached to a lift axle.
A superstructure fitted at the after end of the upper deck of a ship
Ponded roof
Flat roof designed to hold a quantity of water which acts as a cooling device.
PontiacClick image for books on

A vehicle brand of which the Safari for 1955-57 are milestone cars. The GTO for 1964-69 are milestone cars.

Pony car
Small, sporty car along the lines of the Mustang, Firebird, Camaro, etc. especially of the 1960-80.
Poor opacity
A paint fault in which the color of underlying coats or fillers remains visible through the topcoat; may be caused by insufficient paint thickness, overthinning, etc.
Pop-off valve
A one-way valve that opens to the atmosphere above a certain set pressure to relieve excessive internal pressure buildup; often used with a turbocharger installation to limit boost pressure to the engine.
Poppet valve
A valve structure consisting of a circular head with an elongated stem attached in the center, very much like the shape of a mushroom with a flat top. It is designed to open and close a circular hole or Port. Its name comes from the fact that it pops up and down. In engines, it is the valve used to open and close the Valve port entrances to the engine cylinders.
Popping back
Pop rivet
Pop rivetPop rivet

  1. A type of tubular rivet which initially has a hard steel pin (like a nail) passing through it; when the pop rivet is fitted with a pop rivet gun, the head of the pin expands the inner end of the tubular rivet, closing it; the head of the pin then snaps off; used when a joint can be accessed from only one side.
  2. A blind fastener which has a self-contained mandrel which permits the formation of an upset on the blind end of the rivet and expansion of the rivet shank. The mandrel is pulled into or against the body, breaking at or near the junction of the mandrel shank and its upset end.
Pop riveter
Pop riveterPop riveter

A tool into which a pop rivet is inserted so that as the handles are squeezed, the end of the rivet shank is mushroomed to secure the rivet in place. Also called a pop rivet gun.

Pop tester
An injector testing tool used for measuring opening pressure, leakoff pressure, and spray patterns of injectors
A randonneur bicycle event under the regulations and pace of a standard brevet which is less than 200 kilometres.
A towable tent that pops up when parked to expand its space. These types have a furnace, three way refrigerator, a/c, and more options.
Pop-up headlights
  1. The material used to insulate the center electrode of a spark plug, it is hard and resistant to damage by heat.
  2. Ceramic china-like coating applied to steel surfaces.
Porcelain enamel
A glassy material obtained by melting a mixture of inorganic materials; this can then be applied in one or more layers on a metal surface to which it is firmly bonded after firing; typical automotive applications are for badges and trim. The British term is vitreous enamel
A small opening in a surface
Presence of gas pockets or voids in the metal.
Permeable to air or fluids
PorscheClick image for books on

A German vehicle brand of which the Series 356 for 1949-64 are milestone cars. The 356C for 1965 is a milestone car. Includes 911 (1964-current), 924 (1976-88), 928 (1977-95), 944 (1982-91), 968 (1992-95), Boxster (1997-current), Carrera GT (2004-05), Cayenne (2003-06), and Cayman (2006-07)

Porsche-type synchromesh
A sophisticated synchromesh technology depending on the frictional forces created by a spreading synchronizer ring
  1. An opening in an engine cylinder block for exhaust and intake valves and water connections.
  2. To smooth out, align, and somewhat enlarge the Intake passageway to the valves or intake chambers (especially in two-stroke engines).
  3. A small hole in the master brake cylinder to permit fluid to return to the reservoir.
  4. Any opening in a burner head through which gas or gas-air mixture is discharged for ignition.
  5. The left-hand side of a ship when facing forward.
Portable service cylinder
Container used to store refrigerant. Two most common types are disposable and refillable.
Port area
The cross-section area of the port of a two-stroke engine; this value is one of the factors determining the gas flow and the power of a two-stroke engine
Port bar
If the ports of the two-stroke engine have to be exceptionally wide, as in the case of the exhaust, a port bar is sometimes formed vertically across the port to give support to the rings, which might otherwise expand into the port and be jammed and broken
Port bridge
If the ports of the two-stroke engine have to be exceptionally wide, as in the case of the exhaust, a port bar is sometimes formed vertically across the port to give support to the rings, which might otherwise expand into the port and be jammed and broken
Port cover
Ported EGR valve
Operated by a vacuum signal from the carburetor EGR port. The port signal actuates the valve diaphragm. As vacuum increases, spring pressure is overcome, opening the valve and allowing EGR flow. The amount of the flow is dependent on the position of the tapered pintle or poppet whose position reflects the strength of the vacuum signal
Ported vacuum
A slot-type port located right at the throttle plates, used for controlling various devices that must work in proportion to throttle plate opening, such as the EGR valve. When the throttle plates are closed at idle, there is virtually no vacuum signal at this slop. But as the throttle plates open during acceleration, they expose the slot to a progressively increasing amount of intake manifold vacuum
Ported vacuum advance
(PVA) A series of restriction devices between the distributor advance unit and the carburetor advance port to ensure that there is no vacuum advance during idle, but increasing ignition advance as the throttle opens
Ported vacuum switch
(PVS) a temperature actuated switch that changes vacuum connections when the coolant temperature changes (originally used to switch spark port vacuum; now used for any vacuum switching function that requires coolant temperature sensing)
Port fuel injection
(PFI) A type of fuel injection with at least one injector mounted in the Intake port(s) of each cylinder. Usually the injector is mounted on the air intake manifold close to the port. Port fuel injection improves fuel distribution and allows greater flexibility in intake-manifold design, which can contribute to improved engine breathing. Also called Multi-point injection
A styling accessory popularized by the Buicks of the early 1950s where three or four round chrome surrounds were fitted to the sides of both fenders for decorative purposes; this trim detail was soon imitated by other manufacturers and was offered as an option for many models, even in Europe. The T-bird had a porthole window on each the rear sail panels.
Port induction
Port Injection
Port of Entry
(POE) Each state or province has a number of check stops to be sure of compliance of commercial carriers to meet cargo and weight restriction.
Port timing
In 2-stroke engines the critical moment when ports are covered or uncovered by the piston
Abbreviation for Positive ground.
Position sensor
Position welding
Positioning Satellite
Positive camber

Positive caster
When an imaginary line extending through the steering axis cuts the wheel axis ahead of the extended vertical axis through the wheel center.


Positive clutch
Positive connections
Connections in an electric circuit out of which electricity constantly flows. The positive connections out of which electricity flows may also be termed that into which electrons flow; and the negative connection into which electrons flow; and the negative connection into which the electricity flows may be considered that pole out of which the electrons flow.
Positive crankcase ventilation
(PCV) A process introduced in 1963 for preventing the buildup of harmful acid-producing combustion gases within the crankcase.

Positive crankcase ventilation system
(PCV) A process for preventing the buildup of harmful acid-producing combustion gases within the crankcase.

Positive crankcase ventilation valve
(PCVV) a one-way valve which controls the flow of vapors from the crankcase into the engine
Positive displacement compressor
A pump which provides a measured amount of gas or liquid per stroke or cycle and requires some form of mechanical drive arrangement, usually a belt drive from the crankshaft; typical positive displacement compressors are piston compressors, roots compressors and vane-type compressors
Positive electrode
The Positive plate of a battery
Positive ground
An automotive electrical system where the negative post of the battery was the hot wire and the positive post was connected to the frame of the vehicle. Opposite to Negative ground.
Positive offset
  1. A steering geometry layout where the steering axis cuts the wheel axis at or below the wheel center plane.
  2. The distance between the mounting face of a disc and the wheel centerline; the offset is referred to as positive when the inner attachment face of the wheel disc is shifted towards the outer side of the wheel. The opposite is Negative offset
Positive plate
The chocolate-colored plate during battery discharge which acts as cathode. The opposite to negative plate
Positive pole
The point away from which an electrical current flows through the circuit. It is designated by a plus sign (+).
Positive temperature coefficient
(PTC) a thermistor (temperature sensor) whose resistance increases as the temperature increase. The opposite of a negative temperature coefficient (NTC) thermistor
Positive temperature coefficient thermistor
(PTC) Electronic thermistor which increases in resistance as temperature increases.
Positive terminal
The terminal (such as that on the battery), to which the current flows. It is usually marked with the letters pos or a plus sign (+) and is usually red.
Positive Voltage
Possum Belly Trailer
A livestock trailer.
  1. The round, tapered lead posts protruding above the top of the battery to which the battery cables are attached.
  2. The pillars which support the roof on a car.
  3. The insert tube to which the seat of a bicycle is attached.
Post-combustion treatment
  1. Temperature to which a metal is heated after an operation has been performed on the metal (welding, cutting, forming, etc.).
  2. The heating of glow plugs after the engine is started to prevent blue smoke and misfiring during the warm-up phase
The ignition of the air-fuel mixture after the electrical ignition has been shut off
Post Roof
  1. A colloquial term for carburetor.
  2. An abbreviation for a Potentiometer, also called a rheostat
  3. A cylinder.
Potassium permanganate
Used in carbon filters to help reduce odors.
Potato chipped wheel
A bicycle wheel which has been damaged so that it is bent like a potato chip. Also called a taco wheel for a similar reason.
Potato trailer
A hopper bottom or a live bed truck used to carry potatoes.
Potato Truck
A hopper bottom or a live bed truck used to carry potatoes.
Potential, electrical
Electrical force which moves, or attempts to move, electrons along a conductor or resistance.
Potential relay
Electrical switch which opens on high voltage and closes on low voltage.
A deep hole in the surface of a road.
Pothole Repair
The winter is tough on roads and causes many potholes. The pothole area is excavated and then filled with asphalt. The entire operation takes minutes for one pothole, but workers could be on a single road repairing potholes for multiple days, depending on the severity of the potholes.
Pot joint
A universal joint in which the rollers or balls can move freely in an internally grooved cylinder.

Pot life
The rating in hours of the time interval following the addition of accelerator before a chemically curing adhesive or sealer will become too thick to pass viscosity (consistency) requirements. Closely related to working life.
Pot metal
An Alloy that is cast as a unit. It is relatively inexpensive to make, but is easily subject to breakage.
An indication of the amount of available energy.

Potential energy
The mechanical energy possessed by a body due to its position. For example, water in a reservoir above a hydro-electric power station has high potential energy which is converted to work when it drives the Turbines of the power station.
Instrument for measuring or controlling by sensing small changes in electrical resistance. Also called a rheostat.

Pound foot
The unit of measurement for torque. One pound-foot is equal to the twisting force produced when a one-pound force is applied to the end of a one-foot-long lever.
Pound force
Force applied to a one pound mass; has an acceleration of 32.173 ft/s².
Pounds Per Square Inch Gauge
(psig) Pressure measured with respect to that of the atmosphere. This is a pressure gauge reading in which the gauge is adjusted to read zero at the surrounding atmospheric pressure. It is commonly called gauge pressure.
Pour point
The lowest temperature at which a liquid (e.g., oil) will pour or flow, a test of its ability to flow and lubricate in cold weather.
Powder coating
Powder slush molding
A processing technique applied to produce PVC skins. In a preheated rotating mold, a thin layer of PVC dry blend is evenly spread across the mold surface. The mold is transferred to an oven to fuse the PVC skin and is finally cooled in a water-bath
  1. The rate of doing work. It is expressed in mass times distance over a period of time.
  2. Time rate at which work is done or energy emitted.
  3. The rate of producing, transferring, or using energy, most commonly associated with electricity. Power is measured in watts and often expressed in kilowatts (kW) or megawatts (mW). Also known as real or active power. See Active Power, Apparent Power, Reactive Power, Real Power
  4. To provide power to something, e.g., Power up the radio.
  5. Source or means of supplying energy.
Power antenna
Power antennaPower antenna

(PA) or (P.Ant) A radio antenna which automatically moves up and down whenever the radio is turned on or off. It is a telescoping antenna driven by an electric motor.


Power-assist brakes
A braking system that uses engine intake manifold vacuum (or hydraulic pressure) and atmosphere pressure to reduce the braking effort required at the pedal.
Power assisted
A description of a feature that would normally require a lot of human force, but the engine’s hydraulic or vacuum pressure helps to multiply the human effort.
Power assisted brake
Power assisted brakes
Power-assisted steering
(pas) A steering system in which a hydraulic pump powered by the engine helps the driver to turn the steering wheel. Compare Power steering.
Power-assist Unit
Power band
  1. The subjectively defined rpm range over which an engine delivers a substantial fraction of its peak power. The power band usually extends from slightly below the engine’s torque peak to slightly above its power peak.
  2. A certain rpm range in which an engine makes most of its power
Power booster
Power boosterClick image to supersize
Power booster

A device that uses engine vacuum or hydraulic power to assist you in braking the vehicle. Helps the brake pedal to activate the hydraulic pistons in the master cylinder

Power brake
Power brakes
(PB) A conventional Hydraulic brake system that uses engine vacuum to operate a vacuum power piston, the power piston applies pressure to the brake pedal, or in some cases, directly to the master cylinder piston. This system reduces the amount of pedal pressure that the driver must exert to stop the vehicle. Also called ‘vacuum-assisted brakes’ or hydraulic-assisted brakes.

Power burner
A burner in which either gas or air, or both, are supplied at pressures exceeding the line pressure for gas and atmospheric pressure for air, this added pressure being applied at the burner.
Power chamber
The main housing of a vacuum booster internally partitioned in half by a flexible diaphragm. Pressure differentials between the halves move the diaphragm and create application force.

Power closing
Power conditioning
The subsystem that converts the DC power from the (fuel cell) stack subsystem to DC or ac power that is compatible with system requirements.
Power cut-off
A battery master switch
Power cut-off switch
A battery master switch
Power cycle
Power Density
Power distribution
A specific drive torque distribution between front and rear axles in a 4WD system.

Power Efficiency
Power element
Sensitive element of a temperature-operated control.
Power Element Control
Power Exchange
Power factor
  1. Correction coefficient for the changing current and voltage values of AC power.
  2. A measurement of the time-phase difference between the voltage and current in an AC circuit. It is represented by the cosine of the angle of the phase difference. Zero degrees has a power factor of 100%. That means the watts and volt-amperes are equal and there is nothing more than resistance in the circuit. Ninety degrees of angle represents nothing in the way of resistance and only inductance in the circuit. Power factor is also found by the formula: Power Factor = True Power (TP) divided by Apparent Power (AP)
  3. The ratio of the total active power in watts to the total apparent power in volt-amperes (the product of rms voltage and rms current).
Power Gain
(PG) A two-speed automatic transmission offered by General Motors.
Power hood
British term for Electric top
Power Instability
Power loss
The difference between electricity input and output as a result of an energy transfer between two points.
Power Motor
Power output
Power oversteer
In a rear-wheel-drive vehicle, power oversteer creates a Skid when too much power is applied and the rear wheels spin.
  1. The automobile engine regardless of its type.
  2. A packaged, self-contained, automatically operated assembly of integrated systems for generating useful electrical energy and recoverable thermal energy.
A socket for inserting an auxiliary component. It looks very much like a cigarette lighter socket.
Power seat
( The cushions upon which the driver and or passengers sit which is adjusted by a control switch connected to a small electric motor so that the seat can be moved forward or back, up or down, or be tipped forth and aft.


Power servo
A vacuum-operated or electrically-powered device that actuates the duct doors and switches on systems equipped with automatic temperature control
Powershift transmission
A transmission which can be shifted without declutching or decelerating
Power split
Power steering
(PS) A Steering system using hydraulic pressure to increase the Driver’s turning effort. As the driver turns the steering wheel, steering effort is reduced. The pressure is used either in the Gearbox itself or in a hydraulic cylinder attached to the Steering linkage. Also called power-assisted or assisted steering.

Power steering pump
A pump which supplies hydraulic pressure for the power steering system
Power stroke
Power strokePower stroke

The third stroke of the Four-stroke cycle. The piston moves downward from Top dead center to Bottom dead center as a result of the force of combustion acting on the top of the piston.

Power take off

  1. The end of the crank (usually on the other side from the magneto or starter) where the motion of the crank is transferred to the transmission or power output.
  2. A device (usually a pulley) on an engine or wheel which drives a secondary device. A PTO often drives a hydraulic pump, which can power a dump body, concrete mixer or refuse packer. Some designs mount to a standard opening on the transmission, while others attach at the front or rear of the engine.
  3. An outlet from a vehicle engine used to transfer power to towed equipment or machinery.
Power top
A convertible top which is raised and lowered by a hydraulic system or by electricity.

Power to weight ratio
Power-to-weight ratio
The relationship of a vehicle’s horsepower to the weight of a vehicle. The greater the horsepower is in relation to the weight of the car, the faster the car will go and the faster it will accelerate.
Power train
An engine and transmission combination. Sometimes includes the drive shaft, and drive axle.

Powertrain control module
(PCME) An electronics module or a computer that receives input from various engine and/or powertrain related sensors to determine the operating condition of the engine and/or other powertrain components at a particular moment. The module or computer responds to these signal inputs by sending signals to various engine controls to meet predetermined operating instructions for basic engine management. A PCME is the only PCM that could include all other PCMs in one unit.

Powertrain control signals
Signals sent from a powertrain control module to actuators, relays, or solenoids to control the operations of those devices.
Powertrain input signals
Signals from sensors, switches, or solenoids sent to a powertrain control module describing the operational state or condition of those devices at a particular moment.
Power Unit
A truck, or the part of a combination that has the engine.

Power valve
An enrichment unit in a carburetor that is operated by vacuum or mechanical linkage to provide more fuel at wide open throttle.
Power wheelchair
Power wheelchair
Power wheelchair
A wheelchair with an electric motor powered by two 12-volt batteries. The batteries not only propel the unit, but they also provide power for the various controls such as tilt, proximity switches, sip-n-puff, head arrays, infrared switches, and magnetic angle sensors. The three most common types of power wheelchairs are mid-wheel drive, center-wheel drive, and rear-wheel drive. Also called electric wheelchair.
Power window
A side window which is raised and lowered by an electric motor which is operated by a switch. The British term is electric window
Power window lock-out switch
A switch that renders inoperable all electric window controls on the individual windows, except for the master controls on the driver’s door
Power windows
Side windows which are raised and lowered by an electric motor which is operated by a switch. The British term is electric windows
Pozidriv screwdriver
A proprietary type of screwdriver whose tip resembles the Phillips cross-head configuration but with four additional wedges, making eight flanks altogether, which allows a more positive drive and a higher torque.
Abbreviation for Polypropylene
Abbreviation for parts-per-million. Term used in determining extent of pollution existing in given sample of air.
Abbreviation for Polyphenylene oxide
Abbreviation for Ported Pressure Switch (Ford)
  1. Abbreviation for Ply rating
  2. Abbreviation for Pressure Relief
Pratt and Whitney key
(P&W) A bar like a Flat key except the ends are oval shaped.
Abbreviation for Pressure Regulator Control solenoid
A small upper chamber in the cylinder head of a diesel engine, connected to the main combustion chamber by a narrow passage; fuel is injected into the prechamber (also called swirl chamber) where it is ignited before spreading to the main chamber.

Precipitation hardened stainless steel
Type 630 stainless, little used, expensive and not sold as commercial products, it combines corrosion resistance of 300 series stainless with high tensile strength of 400 series.
Precipitation Hardening
Hardening caused by the precipitation of a constituent from a supersaturated solid solution.
Precipitation number
A test to determine the volume of sediment in lubricating oil. While the oil filter will remove much sediment, some still remains, thus when the precipitation number exceeds a specified number, it should be replaced.
Precision insert bearing
A very accurately made replaceable type of bearing, it consists of an upper and lower shell, the shells are made of steel to which a friction type bearing material has been bonded, Connecting rod and Main bearings are generally of the precision insert type.
Precision Machine Screws
Slotted machine screws, milled from bar, cut thread, and are machined finished Class 3A fits.
Precombustion chamber
Pre-combustion chamber
  1. A small chamber located outside the combustion chamber of some cars in which a small amount of rich fuel-air mixture can be ignited to increase fuel efficiency and cut emissions. Found principally on diesel engines and stratified charge engines. Also called pre-chambers.
  2. A chamber in the cylinder head of some diesels where some fuel is injected, ignited, and partly burned before being forced out into the main chamber.
Pre-combustion engine
A diesel engine using Indirect injection. TheBritish term is Indirect injection engine
A process of mixing plastic raw materials with additives
To compress the fuel-oil mixture first
Pre-compression chamber
A chamber below the pistons in a two-stroke engine in which the fuel-oil mixture is initially compressed in order to enable more fresh charge to be fed into the cylinder
Pre-converter vehicle
A car built prior to the enforcement of emission control standards requiring a catalytic converter to be fitted to every new car
Precooler condenser
Used to cool the refrigerant prior to entering main condenser.
Precured tread rubber
Pre-cured rubber, usually of high density and available in various tread designs, is lined with cushion gum before applying to a buffed Casing using the Cold cap method of retreading. Recently it has been applied in some Hot cap molds employing a smooth matrix or other modifications.
Pre-engagedBendix starter
A combination of Bendix and pre-engaged starter drives
Pre-engaged starter
A starter motor in which the solenoid-operated pinion engages with a flywheel ring gear before the full electric current flows; an overrunning clutch enables the pinion to freewheel before disengaging, once the engine has fired
Preferential oxidation
A reaction that oxidizes one chemical rather than another. In fuel cells, the reaction is used to preferentially oxidize carbon monoxide to carbon dioxide from the Reformate stream after the water-gas shift reactor and before the fuel cell. Same as selective oxidation.
Preferential Tariff
Pregnant roller skate
Trucker slang for a Volkswagen Beetle as in ‘Better get over, we got a pregnant roller skate trying to merge ahead.’
Preheater system
A cold starting aid for diesel engines, consisting of glow plugs, a glow-control unit, and a glow plug and starter switch, for preheating the combustion chamber or the intake air up to auto-ignition temperature
  1. Temperature to which a metal is heated before an operation is performed on the metal (welding, cutting, forming, etc.).
  2. The application of some heat prior to the later application of more heat, Cast iron is preheated to avoid Cracking when the welding process is started. A Coil (ignition) is preheated prior to testing.
Preheating zone
A section in Hot-wax flooding units, in which body shells are preheated to 60°C
The fuel charge being ignited before the proper time. Sometimes causes pinging or Detonation. This is the combustion of the fuel-air mixture that is not a result of the spark plug‘s firing, but by high pressure, a flame, or a hot surface.
A bicycle suspension adjustment that usually involves modifying pressure or adjusting the elastomers to ensure that the suspension responds appropriately to the rider’s weight
Adjusting an antifriction bearing, Ball joint, or spring so that it is under mild pressure, this prevents bearing looseness under driving stress.
A lubrication system consisting mainly of an electronically controlled pump that circulates pressurized engine oil to an engine’s vital parts for about six seconds when the ignition is switched on prior to starting the engine; reduces friction during cold starts and prolongs engine life
Honda PreludeClick image for books on
Honda Prelude

A model of automobile manufactured by Honda

Premium Compact SUV
An upscale sport utility vehicle of the Compact SUV size as represented by the following Acura RDX, BMW X3, Infiniti EX35, and Land Rover LR2.
Premium gasoline
Gasoline with a high amount of octane to give it an antiknock index (R+M/2) greater than 90. Includes both leaded premium gasoline as well as unleaded premium gasoline.

Premium Large SUV
Upscale model of a Large SUV such as the following.

Premium Large SUV
Audi Q7 Cadillac Escalade Hummer H2
Infiniti QX56 Land Rover Range Rover Lexus LX 570
Lincoln Navigator Mercedes-Benz GL550-Class Toyota Land Cruiser
Premium Midsize SUV
An upscale Midsize SUV as seen in the following models

Premium Midsize SUV
Buick Enclave Buick Rainier Cadillac SRX Chrysler Aspen
Ford Explorer (Eddie Bauer Edition) Infiniti FX Jeep Grand Cherokees, Land Rover’s LR3
Land Rover Range Rover Sport Lexus GX 470 Lexus RX Lexus RX300
Lincoln MKX Mercedes-Benz R-Class Porsche Cayenne Saab 9-7X Aero
Volkswagen Touareg 2 Volvo XC90
Premixing burner
A power burner in which all or nearly all of the air for combustion is mixed with the gas as primary air.
Pre-owned vehicle
A Used vehicle. A term coined by car dealers to avoid the idea that a second-hand vehicle is used up (i.e., finished its usefulness).
The reinforcing or molding material already impregnated with a synthetic resin
An electric fuel pump usually located in the fuel tank that keeps pressure in the fuel line prior to the main fuel pump to prevent vapor lock.
Prescribed burning
Skillful application of fire to natural fuels that allows confinement of the fire to a predetermined area and at the same time produces certain planned benefits.
Pre-selector gearbox
An arrangement that enables the driver to select a gear speed before he needs it and then depress the clutch pedal when he desires to use the selected gear.
Preselector gearbox
Preset station button
A button for tuning a radio automatically to a preset frequency, i.e., one radio station can be allocated to each button
Press brake
A large type of sheet metal folder, built to handle larger panels and thicknesses
Press, drill
Pressed panel
A panel produced with special press tools and dies, as opposed to a hand-made panel
Pressed steel
Sheet steel made into curved sections by press forming. It is often used in the construction of the frame and forks
Press fit
An Interference fit. A fit so tight that an object must be removed with a Puller or a press.

Pressing plant
A factory specializing in the manufacture of automobile bodies
  1. The force due to the weight of a substance exerted over the area the substance occupies. In metric measure, it is the force acting on each square metre. To calculate pressure, divide the force (in newtons) by the area (in square metres). It is measured in newtons per square metre (N/m²). In Imperial (U.S.) measure, it is measured in pounds per square inch (lb/in.²) (psi).
  2. Energy impact on a unit area; force or thrust on a surface.
  3. Force per unit area. As used in air conditioning systems, it refers to the refrigerant pressure, which is expressed in pounds per square inch (psi)

Pressure, absolute
Pressure accumulator
A spherical pressure tank of about 10 mm diameter in an hydraulic brake booster. A diaphragm separates the pressure accumulator into two chambers, one contains pressurized nitrogen, the other contains hydraulic fluid supplied by the hydraulic pump; pressure inside the accumulator is in the order of 60 bar
Pressure Actuator
Pressure, atmospheric
Pressure, back
Pressure bleeder
  1. A device that forces brake fluid under pressure, into the master cylinder so that by opening the bleeder screws at the wheel cylinders, all air will be removed from the brake system.
  2. A container with a brake fluid and air compartment separated by a diaphragm. Used with adapters to supply a constant, clean pressurized source of brake fluid for bleeding.
Pressure buildup
As a tire heats up as it travels on the road, the air inside the tire expands and thus increases the air pressure. Any increase exceeding 15% above starting cold pressure should be investigated. The practice of Bleeding the excess or hot pressure should be avoided.
Pressure burner
A burner which is supplied with a gas-air mixture under pressure, usually from 0.5 to 14.0 inches water column (1/8 to 3.5kPa) and occasionally higher.
Pressure cap
Pressure capPressure cap

A special cap for the radiator, it holds a predetermined amount of pressure on the water in the cooling system, this enables the water to run hotter without boiling. In this way, the engine can operate at a higher and a more efficient temperature without danger of overheating. The cap also has a vacuum valve that lets air into the cooling system if the pressure falls too low to prevent outside air pressure from causing a partial collapse of the radiator.

Pressure Check Valve
Pressure Control
Pressure Controlled
Pressure Control Valve
Pressure Curve
Pressure Differential
Pressure differential sensor
A detection device that reads pressure changes in the intake manifold in relation to barometric pressure. Also called a manifold pressure sensor, manifold vacuum sensor, or vacuum sensor
Pressure differential switch
A hydraulic pressure-operated switch (often included in a combination valve) which activates the brake failure warning light when one of the brake circuits (in a dual-circuit system) falls due to a system leak and associated pressure drop
Pressure differential valve
  1. Senses unbalanced hydraulic pressure between two halves of the split brake system
  2. A spool-type valve used in dual brake systems to detect any difference in pressure between the systems. Its motion usually operates a switch that sends current to a warning lamp on the instrument panel.
Pressure differential warning switch
A component of the brake hydraulic system that warns the driver of a failure in one of the circuits
Pressure drop
  1. The difference in pressure between two points in the system, usually caused by a restriction device. Specifically the difference in pressure where fuel metering occurs. In electronic injection system, this is the difference between fuel system pressure and intake manifold pressure. In Bosch CIS, it is the difference between system pressure inside the control plunger and the pressure outside the slits, in the upper-chamber of the differential-pressure valves
  2. Pressure difference at two ends of a circuit, or part of a circuit; the two sides of a filter.
Pressure-feed spray gun
A type of spray gun with a separate paint container (pressure-feed tank). It is used mostly for spraying highly viscous materials such as spray putty
Pressure foaming
Pressure forming
Pressure gage
Pressure gauge
Instrument for measuring the pressure exerted by the contents on its container. Reading in pounds per square inch (psi) above atmospheric pressure.

Pressure, head
Force caused by the weight of a column or body of fluids. Expressed in feet, inches, or psi.
Pressure-heat diagram
Graph of refrigerant pressure. heat and temperature properties. (Mollier’s diagram).
Pressure indicator
Pressure limiter
Device which remains closed until a certain pressure is reached, then opens and releases fluid to another part of system or breaks an electric circuit.

Pressure limiting valve
A British term for a Proportioning valve
Pressure Line
Pressure Lubricant
Pressure lubrication
  1. Forced-feed lubrication.
  2. Lubrication system with crankcase scavenging. Fresh oil is supplied from a separate container and lubricates the engine components as it passes through the crankcase. The oil is ignited along with the air/fuel mixture. With this system, it is no longer necessary to add oil to the fuel when filling up
Pressure modulated
Pressure modulated valve
Pressure Monitor System
Pressure motor control
  1. Device which opens and closes an electrical circuit as pressures change.
  2. High- or low-pressure control connected into the electrical circuit and used to start and stop motor. It is activated by demand for refrigeration or for safety.
Pressure-operated altitude valve
(poa) Device which maintains a constant low-side pressure, independent of altitude of operation.
Pressure, operating
Pressure at which a system is operating.
Pressure Period
Pressure plate
  1. The plate that carries the brake pad in a disc brake. Also called Backplate.
  2. The part of the clutch assembly which is pressed against the clutch plate by the clutch springs to transmit the drive.
Pressure pump
Pressure radiator cap
Pressure regulating valve
  1. Any valve which maintains pressure at or under a certain pressure; specifically the pressure relief valve of the oil pump.
  2. In a continuous injection system, part of the fuel distributor, consisting basically of a spring-loaded steel diaphragm which serves to keep the pressure drop across the metering ports at a constant 0.1 bar
Pressure regulator
  1. A spring-loaded diaphragm-type pressure-relief valve which governs the pressure of the fuel delivered to the fuel injectors by the fuel pump and returning the excess to the tank.
  2. A device placed in a gas line for reducing, controlling and maintaining the pressure in that portion of the piping system downstream of the device.
Pressure regulator, evaporator
Automatic pressure regulating valve mounted in suction line between evaporator outlet and compressor inlet. Purpose is to maintain a predetermined pressure and temperature in the evaporator.
Pressure regulator valve
A valve which releases hydraulic fluid if pressure exceeds a preset value

Pressure relief
What you must do to all fuel injection system before cracking a line and opening up the system
Pressure relief valve
  1. A one-way valve designed to open at a specific pressure to prevent pressures in the system from exceeding certain limits. In an engine’s lubrication system, a pressure-relief valve opens to relieve excessive pressure that the oil pump might develop.
  2. A valve which automatically opens and closes a relief vent, depending on whether the pressure is above or below a predetermined value.
Pressure ridge
A work-hardened edge of a damaged panel area that will often remain, even after the area has been smoothed with hammer and dolly; it must then be dressed with hammer and body spoon
Pressure Safety Cutout
Pressure sensing line
A tube that connects the remote bulb to the expansion valve. Also called Capillary tube
Pressure sensing switch
Device, used on some late model GM and Ford vehicle, which cycles compressor operation in accordance with pressure changes sensed at the accumulator
Pressure sensitive adhesive
Type of adhesive that retains its tack or stickiness even after complete release of the solvent
Pressure sensor
Pressure, suction
Pressure in low-pressure side of a refrigerating system.
Pressure switch
Switch operated by a rise or drop in pressure.

Pressure system
Pressure tap
Also called a Fuel-injection system test port
Pressure tire
Pressure Transducer Valve
Pressure Type Check Valve
Pressure-vacuum cap
Fuel tank filler cap designed to prevent loss of fuel or vapor from tank
Pressure valve
Pressure vessel
Containers for the containment of pressure either internal or external. This pressure may be obtained from an external source, or by the application of heat from a direct or indirect source, or by any combination of them.
Pressure Warning
Pressure warning light
Pressure Warning Switch Assembly
Pressure water valve
Device used to control water flow. It is responsive to head pressure of refrigerating system.
Pressure wave
Pulsations or oscillations in the induction and exhaust systems caused by the opening and closing of the valves
Pressure wave supercharger
A supercharger using the pressure waves created by the expanding exhaust gases to compress the inlet charge. Also called Comprex supercharger
Working under pressure
Presta valve
Presta valvePresta valve

A bicycle tube valve whose stem has a small nut on top, which must be loosened during inflation, instead of a spring such as is found on the Schrader valve.

A device that retracts the seat belt to tighten or take up slack in the wearer’s belt. When a collision occurs or when brakes are applied, a seat belt with a pretensioner detects the stopping action and tightens the belt before the wearer is propelled forward. This holds the occupant more securely in the seat.
An engine and gearbox that are not built together in the same casing. Preunit construction was common on earlier motorcycles
PreviaClick image for books on

A model of automobile manufactured by Toyota

The process of applying liquids to salt (before spreading salt on paved roads) to accelerate the ice melting process and prevent salt from bouncing off the road surface.
Price selling
Prick punch
Small, sharp punch used to make punch marks on a metal surface
Primary air
Air introduced into a burner at the mixer head, which mixes with the gas before reaching the port(s).
Primary air inlet
One or more openings through which Primary air is admitted into a burner.
Primary and secondary roads
Primary roads are those designated by an agency to have a higher priority for plowing and sanding; secondary roads are those designated to have lower priority
Primary battery
A non-rechargeable battery consisting of one or more primary cells, used e.g., in portable radio receivers. Opposite to Secondary battery or Storage battery
Primary brake shoe
The brake shoe that is first to press against the Brake drum. The other shoe is the secondary shoe. When both shoes are pressing against the drum, the amplification of forces is called servo action.
Primary catalytic converter
A small converter positioned close to the engine which quickly achieves the necessary operating temperature to reduce exhaust emissions during the warm-up period
Primary cell
An electric cell that converts chemical energy into electrical energy in an irreversible process unlike a secondary cell, it cannot be recharged
Primary chain
The chain of a primary drive
Primary circuit
The low voltage (6 or 12 volts) path of the ignition system which goes from the Positive pole of the battery to the Primary windings of the coil, through the breaker points, and into the ground which leads back to the Negative pole of the battery.
Primary coil
A tube-and-fin circular coil that contains a water glycol solution which surrounds the ignitor and burner. This coil is used in a water glycol gas forced-air furnace.
Primary compression
A term that is used in two-stroke engines. Primary compression takes place in the crankcase and is then pushed up into the combustion chamber where Secondary compression takes place as the piston squeezes the mixture. If the crankcase seals are poor, primary compression will be reduced resulting in reduced Secondary compression so that it may be difficult to start the engine.
Primary compression ratio
The degree of compression achieved in the crankcase area below the piston of a two-stroke engine when the piston moves down and compresses the mixture supplied into the crankcase
Primary control
Device which directly controls operation of heating system.
Primary drive
A drive chain connecting the engine’s crankshaft to its transmission
Primary forward brake shoe
The brake shoe that is installed facing the front of the vehicle, it will be a self-energizing shoe.
Primary fuels
Fuels that can be used continuously. They can sustain the boiler sufficiently for the production of electricity.
Primary ignition
The low-voltage part of the ignition circuit, such as part of the ignition coil wiring, the pickup, electronic ignition module, and ECM. Compare Secondary ignition
Primary key
A key which operates all the locks of the car.

Primary magnetic field
A magnetic field of the primary winding
Primary pattern
The oscilloscope pattern of the primary circuit
Primary piston
  1. The main piston in a tandem master cylinder
  2. In a dual or tandem master cylinder, the piston against which the brake pedal or power booster pushrod bears.
Primary pressure
Also known as system pressure in Bosch continuous injection system
Primary pull-off diaphragm
Device that partially opens the choke when vacuum develops (i.e., when the engine starts), allowing more air to pass through the carburetor, thinning out the excessively rich idle mixture
Primary pump
An engine-driven oil pump feeding pressurized oil to the transmission and hydraulic control system
Primary recovery
The crude oil or natural gas recovered by any method that may be employed to produce them where the fluid enters the well bore by the action of natural reservoir pressure (energy or gravity).
Primary Safety control
A control responsive directly to flame properties; sensing the presence of flame and causing fuel to be shut off in the event of ignition or flame failure requiring manual reset.
Primary seal
The primary piston seal in a tandem master cylinder
Primary shaft
Primary shoe
  1. The shoe of a brake drum system which pivots outwards into the approaching drum. TheBritish term is Leading shoe
  2. The shoe in a duo-servo drum brake that transfers part of its braking force to the secondary shoe
  3. The shoe in a servo brake that transfers a portion of its stopping power to the secondary shoe. The primary shoe provides nearly 30% of the total stopping power.
Primary structure component
Any structural component which, if it collapsed, could make the car uncontrollable or would seriously reduce occupant safety in a crash
Primary terminal
The clip found inside the distributor which allows electric current to pass from the points to the condenser and provides the Insulation to keep the current from contacting other metal parts.
Primary valve
The valve which controls the Primary V-pulley
Primary V-pulley
(CYT) The pulley which is driven by the engine via a clutch; one of its halves can be slid hydraulically, thus varying the diameter of the steel thrust belt track and changing the transmission ratio
Primary winding
The low voltage (6 or 12 volt) windings in ignition coil, the primary winding is heavy wire; Secondary winding uses fine wire.
Primary windings
The low voltage (6 or 12 volt) windings in ignition coil, the primary winding is heavy wire; secondary winding uses fine wire.
Primary wire
Primary wires
The wiring which serves the low voltage part of the ignition system. Wiring from battery to switch, Resistor, ignition coil, distributor points.
  1. To paint bare metal with Primer to prevent rusting. A second color (often different from the prime color) is painted over the primer.
  2. Pronounced PREEM, a stage in a bicycle race.
  3. To fill a machine (e.g., a pump) with the necessary fluid before starting, in order to improve its sealing qualities.
  4. To put fuel in the float chamber of a carburetor to ease the starting of an engine
Prime coat
A Primer or surfacer applied to the old paint or bare metal before the Finish coat is applied.
Prime mover
The engine, turbine, water wheel, or similar machine that drives an electric generator; or, for reporting purposes, a device that converts energy to electricity directly (e.g., photovoltaic solar and fuel cells).
The surfacer that acts as a bond between the bare metal surface or old paint and the color Coat and designed to give rust protection.

Primer bath
A container filled with Primer into which a metal object is submerged. This painting procedure is faster than spray painting and will cover better. The disadvantage is that a lot of primer is required and the metal must be bare of anything else (i.e., glass, rubber, cloth)
Primer filler
A special primer used to cover fine cracks
Primer oven
A painting oven used to dry the coats of primer
Primer surfacer
The material for the resilient coating underneath the top paint coat which provides corrosion protection, protects the paint system from chipping caused by gravel, provides a smooth surface for the top paint coat, and serves as an adhesion promoter. A primer that contains a lot of solid material to fill small imperfections in the substrate (primer-surfacer must be sanded before applying paint over them)
PrincessClick image for books on

An automobile manufactured by British-Leyland

Printed circuit
An electrical circuit made by connecting the units with electrically conductive lines printed on a panel, this eliminates actual wire and the task of connecting it.
Printed circuit board
(pcb) A thin plastic insulating board on one or both sides of which the components and connections of an electronic circuit are formed by etching in a metallic coating or electrodeposition
Priorities List
Priority crossing
See Scramble crosswalk
Prise off
To remove a stubborn object with a lever
Private Carrier
A business which operates trucks primarily for the purpose of transporting its own products and raw materials. The principle business activity of a private carrier is not transportation. Compare For-Hire Carrier.
Private fueling facility
A fueling facility which normally services only fleets and is not open to the general public.
Private Street
A privately owned and maintained access provided for by a tract, easement or other legal means, typically serving three or more potential dwelling units.
PrizmClick image for books on

A model of car produced by the Chevrolet division of General Motors from 1998 to 2002

Abbreviation for the order in which an automatic transmission is displayed to the driver and stands for Park, Reverse, neutral, and Drive. Sometimes, two or more drive positions will be displayed as D1 and D2.
Abbreviation for the order in which an automatic transmission is displayed to the driver and stands for Park, Reverse, neutral, Drive, and Low. Sometimes, the Low may be divided into 3, 2, 1.
  1. A pointed tool, like an icepick. It is used to determine the extent of injuries during the tire inspection.
  2. An Awl.
  3. A measuring sensor, usually long and thin to gain access to narrow cavities.
  4. Ford ProbeClick image for books on
    Ford Probe

    A model of automobile manufactured by Ford

Process Annealing
Heating a ferrous alloy to a temperature close to, but below, the lower limit of the transformation range and then cooling, in order to soften the alloy for further cold working.
Process cooling and refrigeration
The direct process end use in which energy is used to lower the temperature of substances involved in the manufacturing process. Examples include freezing processed meats for later sale in the food industry and lowering the temperature of chemical feedstocks below ambient temperature for use in reactions in the chemical industries. Not included are uses such as air-conditioning for personal comfort and cafeteria refrigeration.
Processed gas
Natural gas that has gone through a processing plant.
Process fuel
All energy consumed in the acquisition, processing, and transportation of energy. Quantifiable process fuel includes three categories: natural gas lease and plant operations, natural gas pipeline operations, and oil refinery operations.
Processing gain
The volumetric amount by which total output is greater than input for a given period of time. This difference is due to the processing of crude oil into products which, in total, have a lower specific gravity than the crude oil processed.
Processing loss
The volumetric amount by which total refinery output is less than input for a given period of time. This difference is due to the processing of crude oil into products which, in total, have a higher specific gravity than the crude oil processed.
Process tube
Length of tubing fastened to hermetic unit dome, used for servicing unit.
A safety system developed by Audi which makes use of the relative displacement of the engine during a frontal collision; steel cables pull the steering wheel away from the driver and increase the seat belt tension
Product carrier
A tanker used to carry refined oil products. Normally four different grades of oil can be handled simultaneously.
Product design
The process of planning the product’s specifications.
Production car
A vehicle model that has been assembled for sale to the general public as opposed to a concept vehicle that is not available to be purchased. Also called production model.
Production engineering
Planning and control of the mechanical means of changing the shape, condition of materials toward greater effectiveness and value.
Production line
A system of assembly in which the parts of an end product are transported by a conveyor past a number of sites where the parts are modified without stopping the conveyor
Production model
A vehicle manufactured by a mass-production process. A vehicle model that has been assembled for sale to the general public as opposed to a concept vehicle that is not available to be purchased. Also called production car.
Production motorcycle
Bikes manufacturer produce to sell to the general public rather than bikes built specifically for racers
Production plant liquids
The volume of liquids removed from natural gas in natural gas processing plants or cycling plants during the year.
Production retread shop
A shop which schedules its production not on the basis of day-to-day orders but rather on long runs of purchased Tire casings in order to secure the lowest cost per unit.
Production vehicle
A vehicle manufactured by a mass-production process. A vehicle model that has been assembled for sale to the general public as opposed to a concept vehicle that is not available to be purchased. Also called production model.
Relative measure of output per labor and/or machine output.
Product line
A series of different products made by the same company which form a group (such as different models of cars)
Product planning
A function whereby an enterprise is responsible for the efficient, planning, scheduling and coordination of production activities.
Product range
A series of different products made by the same company which form a group (such as different models of cars)
Product testing
Rigorous methods whereby a product’s quality and durability are measured.
Professional drivers
Drivers whose main income is from driving, such as bus, coach and haulage drivers
  1. The side view of something.
  2. The aspect ratio of a tire.
Profile depth
Profile ignition pickup
(PIP) a Hall Effect vane switch that furnishes crankshaft position data to the Ford EEC-IV processor
A series of instructions used by the computer.

Program cars
Automobiles sold by manufacturers for fleet use. Usually applies to very large fleets, such as those of car rental companies.
Program comparison and identification
(PCI) A system that identifies a radio station and compares stations to find the station which offers the strongest signal
Programmable controller
A digitally operating electronic system designed for use in an environment, which uses a programmable memory for the internal storage of user-oriented instructions for implementing specific functions such as logic, sequencing, timing, counting and arithmetic to control, through digital or analog inputs and outputs, various types of processes or machines.
Programmable read only memory
  1. (PROM) An electronic component which can be specifically programmed to the design of each car model to control the M/C solenoid. Plugs into the Electronic Control Module (ECM). Also called an Engine calibration unit
  2. A non-volatile memory that stores information permanently. This type of memory cannot be written to. Once programmed, it cannot be altered.
Programmed Fuel Injection
(PGM-FI) Honda’s fuel injection system for the Accord, Civic, Civic CRX, and Prelude
The module that controls blower speed, the air mix door, vacuum diaphragms and other devices in a system equipped with automatic temperature control
Program objectives
A consensus of what has been determined to be the most marketable product for a given model year.
Progressive carburetor
Progressive linkage
A carburetor linkage designed to open the Throttle valves of multiple carburetors. It opens one to start with and when a certain opening point is reached, it will start to open the others.
Progressively wound valve spring
A valve spring with variable spacing between its coils which helps to improve responsiveness and thus to reduce the load on the valve train
Progressive rate spring
A spring with an increasing spring constant. For example, if the first inch of spring motion requires 100 pounds of force, the second inch would require more than an additional 100 pounds, and the third inch would require still more. Progressive-rate springs become stiffer as they are compressed, unlike single-rate springs, which have a fixed spring rate.
Progressive spring
Progressive suspension
A system in which the suspension stiffness changes depending on the amount of change required. On light bumps, the suspension is soft; but on greater bumps, the suspension is stiff.
Progressive transmission
An older version of a manual transmission. When you wanted to go from Low gear to the highest gear, you had to go through all the gears in between. Likewise when you wanted to go from the highest gear to the lowest, you had to proceed through all the Intermediate gears.
Progressive valve spring
A valve spring with variable spacing between its coils which helps to improve responsiveness and thus to reduce the load on the valve train
Projected core/insulator nose
An insulator tip that extends beyond the end of the spark plug shell
Projected spark position
The amount the spark plug gap projects into the combustion chamber 1 mm for the slightly projected spark position in older engines and 3 mm for the normally projected spark position in modern engines
Projection welding
Resistance welding method
Abbreviation for ProgrammableRead Only Memory. PROM contains permanent information about how components should perform under various operating conditions
A substance embedded in the washcoat on catalyst substrates that serves to enhance catalytic efficiency
The speed of action of a governor which depends upon its power relative to the work it must do. The greater the power, the shorter the time required to overcome the resistances.
PRO Number
  1. A number assigned to a shipment by the carrier for tracking purposes.
  2. Any progressive or serial number applied for identification to freight bills, bills of lading, etc.
  3. The nine-digit number used to identify a freight bill, and which corresponds to a scannable bar code. Same as freight bill number.
Prony brake
  1. A device using a friction brake to measure the horsepower output of an engine.
  2. A simple mechanical device, normally made of wood with an adjustable leather strap, that is used to test for the torque output of an electric motor. The prony brake loads the motor and a spring scale attached to it gives a relatively accurate measurement of torque.
Proof load
A test load that a fastener must undergo without showing significant deformation. It is usually 90% of yield strength.

  1. A colorless, flammable gas which is a Petroleum product, similar to and often mixed with Butane. It is useful as an engine fuel or for cooking and heating. In Canada this is the term used for LPG.
  2. A flammable, heavier-than-air gas used in the Halide torch leak detector
  3. Volatile hydrocarbon used as a fuel or as a refrigerant.
Propane air
A mixture of Propane and air resulting in a gaseous fuel suitable for pipeline distribution.
Propane MD-5
A special grade of liquefied petroleum gas composed of a minimum of 90 percent liquid volume of propane (C3H8) and a maximum of 5 percent liquid volume of Propylene (C3H6).
The impeller of a pump, characterized by a small number of blades of double curvature; propellers are generally axial-flow impellers, seldom mixed-flow ones.

Propeller pump
The impeller of a pump, characterized by a small number of blades of double curvature; propellers are generally axial-flow impellers, seldom mixed-flow ones
Propeller shaft
British term for driveshaft. The shaft connecting the transmission Output shaft to the differential pinion shaft.

Propeller shaft safety strap
Propelling power
The force with which a vehicle moves; the pulling force; depends not only on engine power and torque, but also on the amount of friction between driving wheels and road surface
Proper proportion of air and fuel
One of the essential factors in a Combustion engine (Fuel, Air, Proper proportion of mixture, compression, timing, spark).
Property rights
Proper ventilation
In general, the dilution of a flammable gas/vapor with air to a point safely below its lower explosive limit (LEL). As applied to this standard, a sufficient or adequate supply of fresh air and proper exhaust to outdoors or to a safe location with a sufficiently-vigorous and properly distributed air circulation to ensure that the flammable gas/vapor concentration in all parts of the enclosure will be below 25 percent of the LEL at all times.
Being in the proper relative quantity or balance.
Proportional Brake Control
Proportional load synchromesh
The act of distributing something (e.g., brake fluid) to several components in equal measures.

Proportioning valve
  1. Any valve which limits pressure in a system, e.g., in a hydraulic circuit, in automatic transmissions, in pneumatic suspension systems, etc.
  2. The valve used in the rear brake line of some cars with front disc and rear drum brakes. When braking gently, pressure is about equal front and rear; as pedal pressure is increased, the limiting valve controls and finally limits pressure to the rear wheels to prevent rear wheel lockup during heavy braking. The British term for proportioning valve is pressure limiting valve.
  3. A hydraulic valve that reduces pressure to the rear wheel to obtain balanced braking.
  4. A hydraulic control valve located in the circuit to the rear wheels which limits the amount of pressure to the rear brakes to prevent wheel lock-up during panic stops
Proportion Of Air And Fuel
Abbreviation for Propeller shaft.

Prop shaft
Abbreviation for Propeller shaft.

Propulsive power
The force with which a vehicle moves; the pulling force; depends not only on engine power and torque, but also on the amount of friction between driving wheels and road surface
Prop up
To secure the hood, trunk, or liftgate in the open position using the hood support rod.
(C3H6) An Olefinic hydrocarbon recovered from refinery processes or petrochemical processes.
Prospector’s pick
A tool with a long handle (usually made of wood) to which a long curved piece of iron has been attached. At one end of the iron is a point while a blade shape is at the other end.
Prost, Alain
Alain Prost of France is a four-time World Driving Champion. He is the only French Grand Prix driver to win the World Championship in the modern era (1951 through the present). He has won more races than any other driver in Grand Prix racing history. And his 51 wins are a record that will likely stand for a long time.
Protection Act
Protection Agency
Protection Agency Certification Files
Protection System
Protective coat
A layer or layers applied to a surface to provide corrosion protection
Protective coating
A layer or layers applied to a surface to provide corrosion protection
Protective System
Protector, circuit
Electrical device which will open an electrical circuit if excessive electrical conditions occur.
Protector washer
A filter disc between the primary piston and primary seal which supports and protects the primary seal when the brake system is under pressure
A positive charge particle forming part of the atom.
Proton exchange membrane
(PEM) The separating layer in a PEM fuel cell that acts as an electrolyte (which is proton conducting) as well as a barrier film separating the hydrogen-rich feed in the cathode compartment of the cell from the oxygen-rich anode side.
Proton exchange membrane fuel cell
(PEMFC or PEFC) A type of acid based fuel cell in which the exchange of protons (H+) from the anode to the cathode is achieved by a solid, aqueous membrane impregnated with an appropriate acid. The electrolyte is a called a proton-exchange membrane (PEM). The fuel cells typically run at low temperatures (less than 100°C) and low pressures (less than 5 atm).
The test model of a new car design that is intended to be produced in quantity.

Something that projects up slightly from the surrounding surface. Something not Flush. Also called Standing proud or Stand proud
Proved pilot
A pilot flame supervised by a primary safety control.
Pry spoon
Abbreviation for Power steering.
Abbreviation for Pressure Switch Assembly
  1. Abbreviation for Power Steering Control
  2. Abbreviation for Public Service Commission or Public Utilities Commission–The state body which regulates utilities and for-hire trucking operations within a state’s boundaries.
P. seat
Abbreviation for Power seats.
Abbreviation for pounds per square inch — a unit of inflation for a tire, air brake system pressure, and turbocharger boost, or a unit of measurement for an engine’s compression. Normal atmospheric pressure at sea level is 14.7 psi. Metric measurement uses kilopascals.
Abbreviation for pounds per square inch absolute. Absolute pressure equals gauge pressure plus atmospheric pressure.
Abbreviation for pounds per square inch gauge. The G indicates that it is gauge pressure and not absolute pressure.
Abbreviation for Programmable Speedometer Odometer Module
Abbreviation for Purge Shut Off Valve (Ford)
  1. Abbreviation for Power Steering Pressure — Detects power steering load
  2. Abbreviation for pierced steel planking
Abbreviation for Power Steering Pressure Switch
Abbreviation for power sun roof.
Instrument for measuring the relative humidity of atmospheric air. Also called wet bulb hygrometer

Psychrometric chart
Chart that shows relationship between the temperature, pressure, and moisture content of the air.
Psychrometric measurement
Measurement of temperature pressure and humidity using a psychrometric chart.
Abbreviation for Positive temperature coefficient
PT Cruiser
A small car built by Chrysler in its effort to create a ‘retro-look’
PTC heater
Abbreviation for positive temperature coefficient heater
Abbreviation for Power take off. A device (usually a pulley) on an engine or wheel which drives a secondary device. A PTO often drives a hydraulic pump, which can power a dump body, concrete mixer or refuse packer. Some designs mount to a standard opening on the transmission, while others attach at the front or rear of the engine.
Abbreviation for Periodic Trap Oxidizer
Abbreviation for Part Throttle Unlock
(P/U) Common abbreviations for pickup truck.
Public Service Commission
(PSC) the state body which regulates utilities and for-hire trucking operations within a state’s boundaries. Also called Public Utilities Commission
Public Street
Publicly owned facility-providing access, including the roadway and all other improvements, inside the right-of-way.
Public Utilities Commission
(PUC) The state body which regulates utilities and for-hire trucking operations within a state’s boundaries.
Abbreviation for Public Utilities Commission The state body which regulates utilities and for-hire trucking operations within a state’s boundaries.
A paint fault.

Portion of weld that is molten at the place heat is supplied.
Puddle jumper
A colloquial term for a small car. It was used in North America when most cars were very large and was representative of the VW, Austin, Nash Metropolitan, etc.
Puddle lamp
A lamp in the bottom of a luxury car door which illuminates the area into which a passenger is going to step when the door is opened
Puddle welding
Abbreviation for Public Utility Holding Company Act of 1935


  1. The action of a vehicle to deviate towards the side. There may be various causes for a vehicle pulling to one side or the other, the most common being the brakes on either side exerting uneven pressure, incorrect wheel alignment, uneven tire tread, or a defect in the steering system.
  2. The tendency of a car to pull or lead to one side when brakes are applied.
Pull away
To drive away from a standing start
Pull Brakes
A device for separating two components which are secured by Press fitting them.

Puller Slide Hammer
  1. A grooved wheel carrying a string, rope, chain, or belt which turns the wheel.
  2. Flat wheel with a V groove. When attached to a drive and drive members, the pulley provides a means for driving the compressor.
Pulley Holder
Pull in
To drive to the side of the road or into a rest stop, etc.
Pulling beam
A hydraulic ram attached securely to the vehicle at strong points; pulling force is then applied to the pulling beam to pull the frame or sheet metal back into place
Pulling post
A post bolted to the shop floor or secured in a concrete foundation which forms the anchor for the chain and hydraulic jack assemblies to straighten misaligned bodies
Pull-in torque
The maximum constant torque that a synchronous electric motor will accelerate into synchronism at rated voltage and frequency
Pull-in winding
A winding as used in a starter solenoid that does the heavy pull-in work.

Pull it down
A term often used in reference to dismantling and overhauling an engine. Same as tear it down.
Pull off
To drive off a road (and stop)
Pull-off Diaphragm
Pull out
  1. To drive away from the side of a road.
  2. To drive out from behind a vehicle in front in order to overtake (i.e., pass)
Pull-out door handle
An outside door handle which is pulled away from the door skin to open the door
Pull over
To drive to the side of the road and stop
Pullover point
The location of the main circuit discharge in the venturi, which is always higher than the fuel level in the bowl so fuel wont run into the venturi when it shouldn’t. Spillover is determined by the size of the venturi and by the displacement of the engine pulling air through the carburetor. Also called Spillover point
Pull Trailer
A short, full trailer (supported by axles front and rear) with an extended tongue that attaches with either a ball or a pintle hitch.

Pull-type clutch
A clutch in which the clutch release bearing is pulled away from the flywheel when the clutch is disengaged.

Pull up
To get close to and stop as in ‘to pull up to the gas pumps.’
Pull-up torque
The minimum torque delivered by an AC motor during the period of acceleration from zero to the speed at which breakdown occurs. For motors which do not have a definite breakdown torque, the pull-up torque is the minimum toque developed during the process of getting up to the rated speed
Pulp chips
Timber or residues processed into small pieces of wood of more or less uniform dimensions with minimal amounts of bark.
Pulping liquor
(black liquor) The alkaline spent liquor removed from the digesters in the process of chemically pulping wood. After evaporation, the liquor is burned as a fuel in a recovery furnace that permits the recovery of certain basic chemicals.
Pulp wood
Roundwood, whole-tree chips, or wood residues.
A GM system similar to the Air Injection Reaction System (AIR) except there is no Air pump. Instead exhaust pressure pulses draw air into the exhaust system. Fresh air that is filtered by the Air cleaner is supplied to the system on a command from the ECM.
PulsarClick image for books on

A model of automobile manufactured by Nissan in Japan

Pulsation damper
A device used to smooth out the pulsations or surges of fuel from the fuel pump to the carburetor.


Term referring to one cycle of ignition and combustion of a gas-air mixture in a pulse combustion furnace.

Pulse air principle
The method, in air induction systems of introducing secondary air into the exhaust system by means of aspirator valves actuated by the pressure pulses of the exhaust gas stream
Pulse air system
An air induction system using the Pulse air principle. An exhaust emission control system that uses exhaust pulse in a pipe to permit air to be drawn into exhaust system
Pulse arc welding
A type of welding arc in which the arc welding current is interrupted or pulsed as the welding arc progressed.
Pulse combustion process
Repeated ignition of a gas and air mixture in a high efficiency gas furnace.
Pulsed injection
A system that delivers fuel in intermittent pulses by the opening and closing of solenoid-controlled injectors. Also called Electronic fuel injection (EFI)
Pulse former
A circuit for changing the waveform of a signal
Pulse furnace
Furnace which has a tuned (resonant) combustion chamber. Part of the energy normally lost through flue is returned to start next pulse of combustion.
Pulse generator
The pick-up and reluctor assembly. Generates an electrical pulse which triggers the electrical control unit or igniter. Also called a pulse signal generator.

Pulse period
The time available, depending on engine speed, for opening the solenoid injectors
Pulser coil

Pulse relay
Pulse shaper
A circuit for changing the waveform of a signal
Pulse time
The measurement, in milliseconds, of the duration of the signal that activates the fuel injector. In other words, the amount of time that an injector is energized. The duration or pulse width is related directly to the amount of fuel injected into the combustion chamber. Also called Pulse width
Pulse vacuum hublock
This is a new scheme of switching the hubs in a four-wheel-drive vehicle using a pulse of vacuum rather than electrical solenoids, which are heavier and more prone to failure.
Pulse Valve
Pulse width
The measurement, in milliseconds, of the duration of the signal that activates the fuel injector. In other words, the amount of time that an injector is energized. The duration or pulse width is related directly to the amount of fuel injected into the combustion chamber. Also called Pulse time
Pulse-width modulated
(PWM) A continuous on-and-off cycling of an actuator for a fixed number of times per second. Pulse width is usually measured in milliseconds.
Pulse width modulation valve
A normally closed valve, used in some Kelsey Hayes systems on GM vehicles, that opens to release hydraulic pressure from the wheel brake during an ABS stop
  1. As a verb, it means to move something energetically up and down.
  2. A device for moving liquid or gas by decreasing or increasing the pressure on it.
Pump, centrifugal
Pump which produces fluid velocity and converts it to pressure head.
Pump down
  1. The act of using a compressor or a pump to reduce the pressure in a container or a system.
  2. Evacuate
Pump-fed lubrication
Pump, fixed displacement
A pump in which the displacement per cycle cannot be varied.
Pump gasoline
Normal gasoline (whether regular or premium) available at service stations in contrast with racing fuel obtained from specialty locations.
Pump Governor
Pumping chamber
Pumping losses
That part of engine power which is expended on the induction of the fuel and air charge into the engine and the expulsion of combustion gases
Pumping, oil
Pumping the brakes
A method of repeatedly applying the brakes so that optimum braking can be established without creating brake fade. In anti-lock brakes, this procedure is unnecessary.
Pumping the gas pedal
Forcing the accelerator up and down in an endeavor to provide extra gasoline to the cylinders, this is often the cause of Flooding. It is especially harmful to cars with fuel injection.
Pumping the throttle pedal
Forcing the accelerator up and down in an endeavor to provide extra gasoline to the cylinders, this is often the cause of Flooding. It is especially harmful to cars with fuel injection.
Pump inlet check ball
A steel ball located in the plunger head or in the bottom of the accelerator pump well. The pump inlet check ball prevents fuel from escaping from the well when the throttle is opened and pressure is exerted on the fuel in the pump well by the accelerator pump piston
Pumpkin driver
Trucker slang for a driver for Schneider National as in ‘There’s a pumpkin driver ahead.’
Pump-Line-Nozzle Fuel System
A fuel system using a single injection pump driven off the geartrain on the front of the engine that also drives the camshaft. The central injection pump feeds a separate injection nozzle located in the cylinder head above each cylinder. Lines which must be of exactly equal length link each pump plunger with the associated nozzle. Each nozzle incorporates a needle valve and the orifices which actually handle atomization.
Pump Octane
The octane as posted on retail gasoline dispensers as (R+M)/2; same as Antiknock Index.
Pump power output
The energy transferred by a pump to the liquid pumped
Pump, reciprocating single piston
A pump having a single reciprocating (moving up and down or back and forth) piston.
Pump Relay
Pump rotor
A centrifugal pump assembly consisting of the pump shaft, impeller and further rotating components, such as rotating hearing and shaft sealing parts
Pump sag
A hesitation in carburetor performance between the time the accelerator pump squirts fuel into the venturi and the point at which the main fuel circuit is activated
Pump, screw
Pump having two interlocking screws rotating in a housing.
Pump shaft
A shaft which transmits the driver torque to the impeller(s) of centrifugal pumps or to the displacement element(s) of rotary pumps
Pump shut-off
Pump shut-off switch
Pump strainer
Pump switch
Pump the brakes
Pump the gas pedal
Pump the throttle pedal
  1. A tool for making holes or driving out bolts, rivets and pins.
  2. To perforate by pressing a non-rotating tool through the work.
  3. To accelerate a vehicle by rapidly pressing down on the throttle
Punch list
A list of work items kept by an engineer to ensure that all jobs are completed on a project. Similar to a check list.
A penetration of a tire’s air chamber by a foreign object, nail, glass, etc. resulting in loss of air. Such loss can be rapid with the collapse of the innertube, or relatively slow in the case of tubeless tires.
Punt chassis
Abbreviation for Pick-ups (like Ford Blackwood or GM Sierra).
Pup Trailer
A short semitrailer, usually between 26 and 32 feet long, with a single axle. Used in combination with a dolly and another semitrailer to create a twin trailer. Sometimes used to refer to a short semitrailer not in twin combination.

Abbreviation for Polyurethane
Component supplied by an outside manufacturer
Purchase option
Most closed-end leases grant the lessee an option to purchase the vehicle at the end of the lease. The end-of-lease purchase price is usually the same as the stated residual value. Check your lease contract before signing to ensure that there is a purchase option. The lessor must disclose the purchase option price prior to your signing the lease contract.
Purchase price
The price of a vehicle that the consumer pays. Start with the MSRP and subtract any manufacturer discount and dealer discount you negotiate. Purchase price is a key determinant of the true cost of a lease. Purchase price less your down payment and dealer participation equals the net capitalized cost.

Total materials purchased for manufacturing/assembly into auto parts (i.e., steel, plastics, rubber, textiles, etc.).
Bikes intended for off-road use that are not legal to ride on public roads. Sometimes the term pure-dirt is used to distinguish a dirtbike from a dual-sport motorcycle
Pure zinc
  1. To get rid of impurities
  2. To free a gas conduit of air, gas or a mixture of air and gas.
Purge control valve
(PURGE CV) used to control the release of fuel vapors from the charcoal canister into the engine
Abbreviation for Purge control valve
Purge Shut-off Valve
Purge solenoid
A device used to control the operation of the purge valve in an evaporative control emission system

Purge Test
A test used to determine if fuel vapors are properly drawn from the evaporative canister and the fuel tank into the engine for combustion. If the purge system is not working properly, the evaporative canister can become saturated and vent hydrocarbons into the atmosphere.
Purge Time
The period of time intended to allow for the dissipation of any unburned gas or residual products of combustion.
Purge Valve
  1. Releasing compressed gas to atmosphere through some part or parts for the purpose of removing contaminants from that part or parts.
  2. Thorough evacuation of the air conditioning system
Purification system
A machine used for a liquid-liquid separation in which the two intermixed liquids which are insoluble in each other have different specific gravities. Solids with specific gravities higher than those of the liquids can be separated off at the same time. A purifier bowl has two outlets; one for the light phase liquid and one for the heavy phase liquid.
Purple gasoline
Gasoline that has been mixed with an identifying dye (usually purple) and sold for less in order to help farmers. In most places where this is practiced, it is illegal to use purple gasoline in non-farm vehicles. Also called farm gas.
Purpose lacquer
Purpose lacquer thinner
Purpose pliers
Purpose ship
A colloquial term for Understeer.
Push bar
A bar between the shoes in a drum brake
Push bike
Push button
A switch which is engaged by pushing a button in. In most cases there are several Button options so that when one is selected, the previously selected button is pushed back out (de-selected).
A switch which is engaged by pushing a button in. In most cases there are several Button options so that when one is selected, the previously selected button is pushed back out (de-selected).
Pusher axle
A non-powered axle placed ahead of the drive axle in large trucks. Contrasted with a Tag axle which is placed behind the drive axle.
Push-pull Amplifier
Push rod
The rod that connects the Valve lifter to one end of the Rocker arm. Used on valve-in-head installations where the cam is below the piston and the valves are above the piston. The rods are moved by the cam and activate the valve lifter. Engines with overhead cams do not need push rods because the camshaft connects to the valves directly.

Push rod engine
Pushrod engine
Pushrod engineClick image to supersize
Pushrod engine

An engine configuration where the camshafts are located lower in the engine. Connecting rods and other components are used to operate the valves at the top of the cylinder heads

Pushrod measuring tool
A tool which measures the length of pushrod needed in an engine; a pushrod of proper length is vital to keep the rocker in the center of the valve, minimize the risk of breakage and extend the valve guide life
Push start
A procedure of starting a vehicle with a manual transmission by pushing the vehicle with another vehicle or by the power of several strong people or by coasting downhill. Once sufficient speed is obtained and the clutch is disengaged (the pedal or lever is pushed in) and the transmission in second gear, then engaging the clutch. At this point, the engine will turn over and start. This procedure will not work with a vehicle with an automatic transmission. The British term is bump start
Push-type clutch
A conventional clutch in which the clutch release bearing is pushed towards the flywheel when the clutch is disengaged. Compare Pull-type clutch
Put the pedal to the metal
Trucker slang for accelerate, speed up as in ‘Let’s put the pedal to the metal.’
A malleable cement or paste used for repairing minor panel imperfections, e.g., chips or scratches on the filled surface; it is used after normal filling and gives an extremely smooth surface.

Putty knife
A tool for scraping off dirt, carbon, and paint or for applying putty
Abbreviation for photovoltaic
Abbreviation for Ported vacuum advance
  1. Abbreviation for Polyvinyl chloride
  2. Abbreviation for Photovoltaic cell that converts sunlight directly into energy: A method for producing energy by converting sunlight using photovoltaic cells (PVCs) that are solid-state single converter devices. Although currently not in wide usage, commercial customers have a growing interest in usage and, therefore, DOE has a growing interest in the impact of PVCs on energy consumption. Economically, PVCs are competitive with other sources of electricity.
PVC seam sealing
The sealing of seams with PVC sealant to prevent the penetration of corrosive agents
PVC tape
PVC underbody treatment
A treatment of the underbody of a vehicle to protect it from chipping due to gravel or stones and corrosive agents
PVC underseal
A protective PVC coating applied to the underbody of a vehicle
PVC underseal coating
A protective PVC coating applied to the underbody of a vehicle
Abbreviation for Ported vacuum switch. A temperature-activated switch that changes vacuum connections when the coolant temperature changes
Abbreviation for power windows.
P&W key
Abbreviation for Pulse Width Modulation
Abbreviation for pressurized-water reactor
Abbreviation for Power Ground for PCM
A highly visible marker for controlling traffic.
The thermal decomposition of biomass at high temperatures (greater than 200°C in the absence of air. The end product of pyrolysis is a mixture of solids (char), liquids (oxygenated oils), and gases (Methane, carbon monoxide, and carbon dioxide) with proportions determined by operating temperature, pressure, oxygen content, and other conditions.
A device which determines the temperature in various parts of a tire.
Pyroxylin paint
An early type of quick drying synthetic paint.