UPMSP Vocational Automobile key terms

A rechargeable store of electrical energy that supplies current to the starter motor and ignition circuit and is recharged by the alternator while the engine runs.

An engine-driven generator that converts mechanical rotation into alternating current, which is rectified to direct current for charging the battery and running vehicle loads.

A high-torque electric motor with a pinion that engages the flywheel ring gear to crank the engine until it fires and runs on its own.

A control device that limits alternator output voltage to a safe steady level, protecting the battery from overcharging and electrical components from excess voltage.

A threaded component that screws into the cylinder head and produces an electric arc across its electrodes to ignite the compressed air-fuel mixture in a petrol engine.

The moment, measured in degrees of crankshaft rotation before or after top dead centre, at which the spark occurs relative to piston position in the cylinder.

The exact position of a piston at the highest point of its travel in the cylinder, used as the reference point for setting valve and ignition timing.

The ratio of the cylinder volume above the piston at bottom dead centre to the volume remaining above it at top dead centre, indicating how much the charge is squeezed.

The small measured gap between the valve stem tip and the rocker arm or cam follower, allowing thermal expansion so valves still seat fully when hot.

A rotating shaft carrying shaped lobes that open and close the intake and exhaust valves in correct sequence and lift, usually driven from the crankshaft by belt or chain.

A toothed belt that synchronises rotation of the crankshaft and camshaft so valves open at the correct point in each cylinder's cycle.

A heavy disc bolted to the crankshaft that stores rotational energy to smooth out power pulses and carries the ring gear engaged by the starter motor.

A friction assembly between engine and gearbox that can be engaged to transmit drive or disengaged to interrupt it, allowing gear changes and smooth pulling away from rest.

A housing containing sets of gears that multiply engine torque or speed to match road conditions, providing several forward ratios and usually a reverse ratio.

A gear assembly in the axle that splits drive to the two wheels while allowing them to turn at different speeds when the vehicle corners or travels over uneven ground.

A rotating tube, fitted with universal joints, that carries drive from the gearbox output to the final drive of a rear-wheel-drive vehicle.

A flexible coupling that transmits rotary motion between two shafts meeting at a changing angle, commonly used at each end of a propeller shaft.

The temporary loss of braking power caused by heat build-up in friction linings or fluid, reducing the coefficient of friction during repeated or prolonged heavy braking.

A hygroscopic hydraulic liquid that transmits pedal force to the wheel brakes; it must resist boiling under heat and is rated by boiling point in DOT classes.

The pump, operated by the brake pedal, that converts pedal force into hydraulic pressure in the brake lines leading to the wheel cylinders or calipers.

A brake in which hydraulically operated pads clamp a rotating metal disc attached to the wheel, converting motion into heat to slow the vehicle.

The forward or backward tilt of the steering axis from vertical, which gives self-centring steering feel and straight-line stability.

The inward or outward tilt of a wheel's top from vertical when viewed from the front, affecting tyre wear and cornering grip.

The amount by which the front edges of a pair of wheels are closer together (toe-in) or further apart (toe-out) than the rear edges, adjusted to control tyre scrub.

A hydraulic damper that controls the rate of suspension spring oscillation, converting bounce energy into heat so the wheels stay in contact with the road.

An elastic member, usually coil, leaf, or torsion bar, that supports vehicle weight and absorbs road shocks before they reach the chassis.

Adjustment of suspension angles, principally camber, caster, and toe, so wheels roll correctly and tyres wear evenly.

A heat exchanger at the front of the vehicle through which coolant circulates, transferring engine heat to air passing through its fins and tubes.

A temperature-sensitive valve that stays closed while the engine warms up and then opens to allow coolant flow through the radiator, holding operating temperature steady.

A mixture of water and antifreeze additive circulated through the engine and radiator to carry away combustion heat and prevent freezing or corrosion.

A measure of an oil's resistance to flow at a stated temperature; multi-grade oils such as 15W-40 are rated for both cold starting and hot running conditions.

A replaceable cartridge that traps metal particles, sludge, and carbon from circulating engine oil so they cannot reach and score bearing surfaces.

A gear or rotor type pump driven from the crankshaft or camshaft that pressurises engine oil and forces it through galleries to bearings and moving parts.

A device that mixes petrol with air in the correct proportion for combustion by drawing fuel through a jet into the incoming air stream.

A system that sprays metered fuel under pressure into the intake manifold or directly into the cylinder, replacing the carburettor for more precise mixture control.

The proportion by mass of air to fuel supplied to the engine; roughly 14.7 to 1 is chemically ideal for petrol, with richer or leaner mixtures used for power or economy.

A diagnostic check that measures peak cylinder pressure with a gauge screwed into the spark plug or injector hole, revealing worn rings, valves, or head gasket leaks.

A vehicle self-monitoring system that stores fault codes from sensors and actuators and makes them available through a diagnostic connector for scan tool reading.

A hand-held or PC-based device that plugs into the diagnostic connector to read fault codes, view live sensor data, and clear codes after repair.

The removable casting bolted on top of the cylinder block that closes the cylinders and houses combustion chambers, valve gear, and often the camshaft.

A precision measuring instrument with a calibrated screw and thimble, used in the workshop to measure shaft diameters and thicknesses to hundredths of a millimetre.

A measuring tool with a sliding jaw and a vernier scale that reads outside, inside, and depth dimensions to a typical resolution of 0.02 millimetre.

A set of thin steel blades of known thickness used to check small gaps such as valve clearances, spark plug gaps, and contact breaker points.

A wrench that slips or signals when a preset tightening torque is reached, ensuring bolts and nuts are clamped to the manufacturer's specified value.

Lifting equipment used together for safe under-vehicle work: the jack raises the vehicle and rigid stands support it, so nobody relies on hydraulic pressure alone.

Safety clothing and gear such as goggles, gloves, safety shoes, and ear defenders worn to protect the technician from injury during workshop tasks.

A portable device for putting out small fires; workshops keep dry powder or CO2 types near fuel and electrical areas and staff must know how to use them.

The structural frame or unitary body shell that carries the engine, suspension, and body panels and absorbs the loads imposed by the road and payload.

The first coating applied to bare prepared metal or body filler, providing adhesion for later coats and corrosion protection for the panel.

A paste applied to dents and uneven panels to restore shape before sanding; it must be smoothed level and sealed with primer before painting.

A volatile solvent used to reduce paint viscosity for spraying and to clean spray guns and brushes; it evaporates after the film is applied.