ASVAB Study GuideAuto & Shop Information Practice Test 4
Tap an answer to check it instantly and read the explanation. 10 questions: 3 easy, 4 medium and 3 hard.
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Question 1 easy
What engine component connects the piston to the crankshaft, transforming reciprocating motion into rotational motion?
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Correct answer: B — connecting rod
The connecting rod links the piston pin to the crankshaft journal, transmitting force from combustion to rotate the crankshaft.
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Question 2 easy
What primary emissions control component in the exhaust system muffles and reduces noise created by engine combustion?
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Correct answer: D — muffler
The muffler contains baffles and chambers designed to dampen pressure waves and reduce noise emitted from engine exhaust gases.
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Question 3 easy
In a gasoline engine fuel system, what component creates high fuel pressure to spray atomized fuel directly into the air stream or combustion chamber?
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Correct answer: A — fuel injector
Fuel injectors use electronically controlled valves to spray finely misted fuel into the intake port or cylinder for efficient combustion.
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Question 4 medium
What cooling system component opens and closes based on temperature to regulate coolant flow between the engine block and radiator?
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Correct answer: C — thermostat
The thermostat remains closed during engine warm-up to heat the engine quickly, then opens at a specific temperature to circulate coolant through the radiator.
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Question 5 medium
Which shaft in an engine is driven by the crankshaft to open and close intake and exhaust valves at precise times?
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Correct answer: A — camshaft
The camshaft features egg-shaped lobes that push against valve lifters or rocker arms to actuate engine valves in perfect synchronization with piston movement.
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Question 6 medium
What specific pollutant level is primarily reduced by recirculating exhaust gases back into the engine cylinder via the EGR system?
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Correct answer: C — nitrogen oxides (NOx)
The EGR system lowers peak combustion temperatures, which directly prevents the formation of harmful nitrogen oxides (NOx).
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Question 7 medium
Unlike gasoline engines, why do diesel engines not require spark plugs for fuel ignition?
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Correct answer: A — high cylinder compression heats the intake air enough to auto-ignite the injected fuel
Diesel engines rely on high compression ratios (typically $$15:1$$ to $$22:1$$) to compress intake air, raising its temperature above the auto-ignition point of diesel fuel.
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Question 8 hard
Why are glow plugs specifically necessary in diesel engines during cold weather starting conditions?
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Correct answer: D — cold cylinder walls absorb heat during compression, preventing air from reaching auto-ignition temperature without auxiliary heating
During a cold start, cold engine metal absorbs thermal energy from compressed air. Glow plugs preheat the combustion chamber air so it reaches the required auto-ignition temperature.
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Question 9 hard
What unwanted physical condition occurs inside the engine crankcase if a Positive Crankcase Ventilation (PCV) valve gets stuck completely closed?
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Correct answer: B — excessive pressure builds up, leading to oil leaks past gaskets and seals
A closed PCV valve traps blow-by gases inside the crankcase, causing pressure to build up until engine seals and gaskets fail and leak oil.
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Question 10 hard
How do oil galleries deliver pressurized engine oil from the main bearings to the connecting rod bearings inside a crankshaft assembly?
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Correct answer: A — through internal cross-drilled oil passages machined inside the crankshaft journal web
Engine oil flows into main bearings from the main oil galleries and then passes through drilled internal passages inside the crankshaft to lubricate the rod bearings.