Engines Exam Practice Questions And

ASE Medium-Heavy Truck T1 Gasoline Engines Exam Practice Questions And Correct Answers (Verified Answers) Plus Rationales 2026 Q&A | Instant Download Pdf

• What is the primary purpose of a cylinder compression test?
• Measure oil pressure
• Measure fuel flow
• Measure the sealing capability of the combustion chamber
• Measure exhaust gas temperature

Rationale: A compression test evaluates the condition of valves,

piston rings, and head gasket by determining if the combustion chamber can hold pressure properly.

• Which component controls valve timing in a modern gasoline engine?
• Oil pump
• Camshaft 1 / 4

• Crankshaft pulley
• Timing belt tensioner

Rationale: The camshaft opens and closes the intake and exhaust

valves at the correct times for efficient engine operation.

3. A knocking noise under load is most likely caused by:

• Loose belts
• Pre-ignition or detonation
• Low oil level
• Worn brake pads

Rationale: Knocking occurs when fuel ignites prematurely or

unevenly, causing abnormal combustion pressures.

• What is the correct firing order for a typical inline six-cylinder gasoline

engine?

A. 1-3-2-6-4-5

B. 1-2-3-4-5-6

C. 1-5-3-6-2-4

D. 1-4-2-5-3-6

Rationale: The firing order is designed to balance engine forces and

reduce vibration.

• During a visual inspection, you notice excessive oil in the spark plug

wells. What is the likely cause?

• Faulty fuel injectors
• Leaking valve cover gasket 2 / 4

• Clogged PCV valve
• Low coolant level

Rationale: Oil can leak into spark plug wells when the valve cover

gasket deteriorates or seals fail.

• Which sensor provides the ECU with information about engine

temperature?

• Oxygen sensor
• Throttle position sensor
• Coolant temperature sensor
• Knock sensor

Rationale: The coolant temperature sensor measures engine

temperature to adjust fuel mixture and timing.

• What is the function of the PCV (Positive Crankcase Ventilation)

system?

• Increase fuel pressure
• Remove blow-by gases from the crankcase
• Cool the radiator
• Control exhaust emissions directly

Rationale: The PCV system routes gases back into the intake

manifold to be burned, reducing emissions and preventing pressure buildup.

• Which type of ignition system is common in modern gasoline engines?
• Distributor with points 3 / 4

• Magneto
• Distributorless ignition system (DIS)
• Flywheel ignition

Rationale: Most modern engines use DIS for more precise spark

timing and reduced maintenance.

9. Engine misfires are often caused by:

• Faulty wiper blades
• Low transmission fluid
• Faulty spark plugs or ignition coils
• Low tire pressure

Rationale: Misfires occur when the air/fuel mixture fails to ignite

properly, usually due to ignition or fuel delivery issues.

• What is the purpose of the knock sensor?
• Measure airflow
• Detect engine detonation
• Monitor oil level
• Control the thermostat

Rationale: The knock sensor detects abnormal combustion and

signals the ECU to adjust timing to prevent engine damage.

• Which tool is required to measure valve lash on a gasoline

engine with mechanical lifters?

• Torque wrench
• Compression gauge
• / 4