ASVAB (Shop & Mechanic)

Four-stroke cycle

stages of engine operation: intake, compression, power, and exhaust.

Intake stroke

Piston moves down, pulling air-fuel mixture into the cylinder

Compression stroke

Piston moves up, compressing the air-fuel mixture before ignition.

Power stroke

Spark plug fires, igniting the mixture and forcing the piston down to generate power.

Exhaust stroke

Piston moves up pushing burned gases out of the cylinder.

Spark plug

Delivers the electrical spark that ignites the air-fuel mixture in the cylinder.

Alternator

Generates electricity while the engine runs, keeping the battery charged.

Radiator

Dissipates engine heat by passing coolant through fins exposed to airflow.

Thermostat

Regulates engine temperature by controlling coolant flow to the radiator.

Carburetor

Mixes air and fuel before sending it to the engine; largely replaced by fuel injection.

Fuel injector

Electronically controlled nozzle that sprays precise amounts of fuel into the engine.

PCM (Powertrain Control Module)

The car's main computer that controls fuel, ignition, and engine functions using sensor data.

Catalytic converter

Converts harmful exhaust pollutants into less harmful gases before they exit the tailpipe.

Differential

Allows wheels on the same axle to spin at different speeds, essential when turning.

Timing belt/chain

Keeps the crankshaft and camshaft synchronized so valves open and close at the right time.

Master cylinder

Converts brake pedal pressure into hydraulic pressure to activate the brakes.

Torque wrench

Measures and limits the rotational force applied to a fastener to prevent over-tightening.

Box-end wrench

Closed-loop wrench that fully surrounds a bolt head for maximum grip.

Open-end wrench

U-shaped wrench that slides onto a bolt from the side; faster but less secure grip.

Combination wrench

Has a box end on one side and an open end on the other.

Allen wrench (hex key)

L-shaped tool that drives fasteners with a hexagonal recess.

Needle-nose pliers

Long, narrow-jawed pliers for gripping small parts in tight spaces.

Locking pliers (Vise-Grips)

Pliers that lock onto an object with adjustable clamping force.

Tap

Cutting tool that creates internal (female) threads inside a drilled hole.

Die

Cutting tool that creates external (male) threads on a rod or bolt.

Ball-peen hammer

Hammer with a flat face for striking and a rounded peen for shaping metal.

Dead blow hammer

Weighted hammer that absorbs rebound to prevent surface damage.

Hacksaw

Fine-toothed saw designed to cut metal, plastic, or pipe.

Micrometer

A precision measuring tool used to measure thickness or diameter to the thousandth of an inch.

Feeler gauge

A set of thin metal blades used to measure small gaps, such as spark plug gap or valve clearance.