NOCTI Automotive Technology

Question 1

What is the primary function of the crankshaft in an internal combustion engine?

Accepted Answer

Convert reciprocating piston motion into rotational motion

Answer

The crankshaft converts the up-and-down (reciprocating) motion of the pistons into the rotational motion that drives the drivetrain.

Question 2

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

Accepted Answer

Head gasket

Answer

The head gasket seals the joint between the cylinder head and engine block, preventing combustion gases, coolant, and oil from mixing.

Question 3

What does the acronym 'OHC' stand for in engine design?

Accepted Answer

Overhead Camshaft

Answer

OHC stands for Overhead Camshaft, meaning the camshaft is located in the cylinder head above the valves rather than in the block.

Question 4

What is the purpose of the PCV (Positive Crankcase Ventilation) valve?

Accepted Answer

Recirculate crankcase blow-by gases back into the intake manifold

Answer

The PCV valve routes unburned gases from the crankcase back into the intake manifold to be burned in the engine, reducing emissions.

Question 5

When performing a compression test and one cylinder shows significantly lower compression than the others, which component is most likely worn?

Accepted Answer

Piston rings or cylinder wall

Answer

Worn piston rings or a scored cylinder wall allow combustion gases to bypass the piston, resulting in low compression in that cylinder.

NOCTI - National Occupational Competency Testing Institute Practice Test