ASVAB Auto and Shop: Engine Systems and Repair 2

Question 1

What is the purpose of the camshaft in a 4-stroke engine?

Accepted Answer

Open and close intake and exhaust valves

Answer

The camshaft uses lobes to push on valve lifters, opening and closing the intake and exhaust valves at precisely timed intervals.

Question 2

A car engine runs hot and the temperature gauge reads high. The coolant level is normal. What is the most likely cause?

Accepted Answer

Faulty thermostat stuck closed

Answer

A thermostat stuck in the closed position prevents coolant from circulating through the radiator, causing the engine to overheat.

Question 3

Which engine component seals the combustion chamber between the cylinder head and engine block?

Accepted Answer

Head gasket

Answer

The head gasket forms a seal between the cylinder head and the engine block to contain combustion pressure and prevent coolant or oil leaks.

Question 4

What does a PCV (Positive Crankcase Ventilation) valve do?

Accepted Answer

Vents crankcase gases back into the intake manifold

Answer

The PCV valve recirculates blow-by gases from the crankcase back into the intake manifold to be burned, reducing emissions.

Question 5

An engine has low compression in one cylinder. What is the most likely cause?

Accepted Answer

Worn or damaged piston rings

Answer

Worn piston rings allow combustion gases to bypass the piston and escape into the crankcase, reducing compression in that cylinder.

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