ASVAB — All Questions

Which engine component converts the up-and-down motion of the pistons into rotating motion?

• a.Radiator
• b.Spark plug
• c.Camshaft
• d.Crankshaft✓

The crankshaft is connected to the pistons and turns their linear up-and-down motion into rotational motion that drives the wheels. The camshaft instead controls the valves.

What is the main purpose of engine oil?

• a.To lubricate moving parts✓
• b.To inflate the tires
• c.To power the lights
• d.To cool the cabin

Engine oil lubricates moving metal parts to reduce friction and wear. It also helps carry away heat and keep internal components clean.

A spark plug is used to:

• a.ignite the fuel-air mixture✓
• b.charge the battery
• c.cool the engine
• d.filter the oil

In a gasoline engine, the spark plug produces an electric spark that ignites the compressed fuel-air mixture in the cylinder. This controlled ignition powers the piston stroke.

Which tool is best for measuring the gap of a spark plug?

• a.Hacksaw
• b.Feeler gauge✓
• c.Pipe wrench
• d.Torque wrench

A feeler gauge has thin blades of known thickness used to measure small gaps, such as a spark plug gap. A torque wrench instead measures tightening force.

The part of the car that keeps the engine from overheating by circulating coolant is the:

• a.radiator✓
• b.alternator
• c.distributor
• d.muffler

The radiator transfers heat from the circulating coolant to the outside air, keeping the engine at a safe temperature. The alternator, by contrast, generates electricity.

A Phillips screwdriver is designed to fit a screw head shaped like a:

• a.hexagon
• b.square
• c.cross✓
• d.straight slot

A Phillips screwdriver has a cross-shaped, or X-shaped, tip that matches a screw head with a cross-shaped recess. A flat-blade screwdriver instead fits a single straight slot.

Which part of a car stores electrical energy to start the engine?

• a.Muffler
• b.Fuel pump
• c.Carburetor
• d.Battery✓

The battery supplies the electrical current needed to power the starter motor and start the engine. Once running, the alternator recharges the battery.

The device that reduces engine exhaust noise is the:

• a.alternator
• b.clutch
• c.radiator
• d.muffler✓

The muffler is part of the exhaust system and dampens the loud noise created by the engine's exhaust gases. It does not affect engine cooling or charging.

A torque wrench is used to:

• a.measure voltage
• b.cut metal pipe
• c.tighten bolts to a specific tightness✓
• d.sand wood surfaces

A torque wrench applies a precise, measured amount of turning force to a bolt or nut. This prevents fasteners from being too loose or over-tightened and damaged.

Which type of saw is designed for cutting metal?

• a.Crosscut saw
• b.Hacksaw✓
• c.Chainsaw
• d.Coping saw

A hacksaw has a fine-toothed blade held under tension in a frame and is made for cutting metal and plastic. A crosscut saw and chainsaw are intended for wood.

The system that allows a car to slow down and stop is the:

• a.fuel system
• b.exhaust system
• c.braking system✓
• d.cooling system

The braking system uses friction, typically pads pressing on discs or rotors, to slow the wheels and stop the vehicle. The fuel and exhaust systems handle power, not stopping.

Which tool would you use to drive a nail into wood?

• a.Pliers
• b.Wrench
• c.Hammer✓
• d.Level

A hammer delivers a strong impact to drive nails into wood. Wrenches turn bolts, pliers grip objects, and a level checks whether a surface is horizontal.

In a four-stroke engine, which stroke immediately follows the compression stroke?

• a.Intake stroke
• b.Cooling stroke
• c.Exhaust stroke
• d.Power stroke✓

The four-stroke cycle runs intake, compression, power, then exhaust. After the fuel-air mixture is compressed, the spark plug fires and the power stroke pushes the piston down.

The purpose of a vehicle's transmission is to:

• a.cool the engine oil
• b.transfer engine power to the wheels✓
• c.store fuel
• d.clean the exhaust gases

The transmission uses gears to transfer the engine's power to the wheels while matching engine speed to driving conditions. Lower gears provide more force, higher gears more speed.

What is the main job of the alternator?

• a.to regulate the flow of fuel to the engine
• b.to store current for the starter motor
• c.to start the engine when the driver turns the key
• d.to recharge the battery while the engine runs✓

The alternator is driven by the engine and supplies the electrical system while replacing the charge the starter drew from the battery. Cranking the engine is the starter motor's job.

What does the thermostat in a cooling system do?

• a.it warns the driver of an overheated engine
• b.it pumps coolant through the engine block
• c.it blocks coolant flow until the engine warms up✓
• d.it cools the coolant before it reaches the engine

A closed thermostat keeps coolant out of the radiator so the engine reaches operating temperature quickly, then opens to let heat escape. The water pump does the pumping.

Besides lubricating, which of the following does engine oil also do?

• a.it carries heat away from moving parts✓
• b.it raises the compression in the cylinders
• c.it improves the spark at the plug gap
• d.it cools the passenger compartment

Oil films the bearings and rings, but it also carries heat out of the engine and suspends contaminants until the filter traps them.

What is the correct order of the strokes in a four-stroke gasoline engine?

• a.intake, compression, power, exhaust✓
• b.intake, power, compression, exhaust
• c.power, intake, compression, exhaust
• d.compression, intake, power, exhaust

The piston draws in the mixture, compresses it, is driven down by the burning charge, and then pushes the spent gases out.

How is the fuel mixture ignited in a diesel engine?

• a.by exhaust gas recirculation
• b.by a heated glow plug
• c.by a spark plug
• d.by the heat of compression✓

A diesel compresses air until it is hot enough to ignite the fuel injected into it, so no spark or arc is needed. Glow plugs, where fitted, only warm the chamber for cold starting.

What does the clutch do in a manual transmission vehicle?

• a.it holds the vehicle still on a hill
• b.it chooses which gear ratio will be used
• c.it locks the drive wheels together
• d.it disconnects engine and transmission✓

Pressing the clutch pedal separates the flywheel from the transmission input shaft so gears can be changed without the engine driving them. Choosing the ratio is the gearbox's job, not the clutch's.

In a disc brake, the pads are squeezed against which part?

• a.the rotor✓
• b.the axle
• c.the drum
• d.the wheel rim

A caliper presses the pads onto both faces of the rotor that spins with the wheel. Drums belong to the other main brake design.

What is the purpose of the catalytic converter?

• a.it makes exhaust gases less harmful✓
• b.it quiets the noise of the exhaust
• c.it increases engine power output
• d.it cools the exhaust manifold

The converter promotes reactions that turn carbon monoxide and unburned fuel into carbon dioxide and water. The muffler is what quiets the exhaust.

What does the differential allow the drive wheels to do?

• a.turn at different speeds in a corner✓
• b.turn at exactly the same speed
• c.spin freely when the car is parked
• d.reverse without shifting gears

In a turn the outside wheel travels farther than the inside wheel, and the differential lets them rotate at different rates while both receive power.

A tire that is consistently underinflated will usually show wear

• a.evenly across the entire tread width
• b.on one edge of the tread only
• c.on both outer edges of the tread✓
• d.down the center of the tread

Low pressure lets the tread bow upward in the middle so the shoulders carry the load. Overinflation produces the opposite pattern, wear down the center.

What does antifreeze added to the cooling system do?

• a.it thickens the coolant to improve the heat transfer
• b.it protects against freezing but not boiling over
• c.it protects against both freezing and boiling over✓
• d.it protects against boiling over but not freezing

A glycol and water mixture protects against freezing in winter and against boil-over in summer, which is why it stays in the system year round.

What component builds the hydraulic pressure when the brake pedal is pressed?

• a.the master cylinder✓
• b.the proportioning valve
• c.the brake booster
• d.the wheel bearing

The pedal pushes a piston in the master cylinder, which sends pressurized fluid to each wheel. The booster only reduces the pedal effort required.

A saw designed to cut across the grain of a board is called

• a.a crosscut saw✓
• b.a coping saw
• c.a rip saw
• d.a metal hacksaw

Crosscut teeth are filed to sever wood fibers across the grain, while rip teeth act like tiny chisels for cutting along the grain. A hacksaw is for metal.

Which tool measures to the nearest thousandth of an inch?

• a.a framing square
• b.a folding rule
• c.a tape measure
• d.a micrometer✓

A micrometer's precision screw and vernier scale resolve 0.001 inch. A rule or tape measure is generally read to a sixteenth of an inch.

What is a hand plane used for?

• a.driving fasteners in flush
• b.boring holes through a board
• c.cutting joints in sheet metal
• d.smoothing a wood surface✓

A plane's blade projects slightly below the sole and removes a thin shaving with each pass, flattening and smoothing the surface.

A hand file cuts on which stroke?

• a.neither, it only polishes
• b.both strokes equally
• c.the return stroke
• d.the forward stroke✓

File teeth point forward, so cutting happens on the push. Dragging the file back under pressure dulls the teeth.

A wood chisel should be struck with

• a.a claw hammer
• b.a ball-peen hammer
• c.a mallet✓
• d.a heavy wrench

A wooden or soft-faced mallet drives the chisel without mushrooming its handle. Steel hammer faces damage the chisel and can chip.

Which tool cuts internal threads inside a drilled hole?

• a.a countersink
• b.a tap✓
• c.a reamer
• d.a die

A tap cuts threads inside a hole and a die cuts threads on the outside of a rod. A reamer only sizes and smooths an existing hole.

Why is a countersink used before driving a flat-head screw?

• a.so the head finishes flush✓
• b.so the screw grips harder
• c.so the hole is sealed against water
• d.so the screw comes out faster

The countersink cuts a cone-shaped recess that matches the underside of a flat head, letting it finish level with the surface.

Why is a pilot hole drilled before driving a wood screw into hardwood?

• a.to keep the screw from rusting
• b.to make the screw hold more tightly
• c.to allow the screw to be countersunk
• d.to keep the wood from splitting✓

The screw's shank displaces wood as it enters, and in dense hardwood that pressure can split the board. A pilot hole removes that material in advance.

On sandpaper, a higher grit number indicates

• a.a wider sheet
• b.a finer abrasive✓
• c.a coarser abrasive
• d.a tougher backing

Grit numbers count the particles that pass a screen, so a larger number means smaller particles and a finer finish.

A ball-peen hammer is intended mainly for

• a.metalwork✓
• b.setting tile
• c.driving nails
• d.shaping stone

The rounded peen is used for riveting and shaping metal. Nails are driven with a claw hammer, which also pulls them.

What is a miter box used for?

• a.storing chisels in order
• b.measuring the board thickness
• c.clamping the stock to a bench
• d.guiding a saw at an angle✓

The slots in a miter box hold the saw at a fixed angle, commonly 45 or 90 degrees, so repeated cuts match.

A plumb bob is used to check

• a.that a corner is square
• b.that a line is vertical✓
• c.that a board is flat
• d.that a line is horizontal

A weight hanging on a string settles along the direction of gravity, which is by definition vertical. A spirit level checks horizontal, and a square checks corners.