ASE A1 Engine Repair Practice Test
6. A spark plug's electrode is covered with thick black carbon deposits. Which of the following is correct?
- A. The engine has a vacuum leak.
- B. This reading shows normal wear.
- C. The piston rings are worn.
- D. The fuel injector is leaking.
Answer A is wrong. White carbon deposits around the electrode indicate a lean fuel condition.
Answer B is wrong. Light tan or light gray colored spark plug tip is considered normal. Today’s fuel-injected engines usually turn the tip a light gray color. The center electrode should be square, not rounded; this is because spark readily jumps off a square edge.
Answer C is correct. A bad valve, valve seals, or worn piston rings result in oil burning in the combustion chamber and black carbon deposits on the spark plug tip.
Answer D is wrong. Black flakey soot on the tip and electrode indicates a rich fuel condition. If a spark plug is wet, it could be oil, fuel, or coolant. A dripping fuel injector will result in a wet spark plug tip that smells like raw fuel.
7. One spark plug's ceramic insulator is longer than the others. Which of the following is correct?
- A. Spark plugs have different heat ranges.
- B. Spark plugs are self-cleaning.
- C. Spark plug resistance can be tested using a digital multimeter.
- D. All of the above.
Answer A is wrong. Spark plugs have different heat ranges and thread lengths.
Answer B is wrong. A spark plug must be hot enough to prevent fouling, yet cool enough to avoid pre-ignition or detonation.
Answer C is wrong. A hot spark plug self cleans better than a cold plug, but a cold plug is better at preventing pre-ignition. Pre-ignition occurs when the air/fuel charge has burned too soon, and detonation occurs when the air/fuel charge burns too fast.
Answer D is correct. A hot plug is generally longer than a cold plug. A spark plug with a high heat range runs cleaner but can cause ping, detonation, and pre-ignition problems. Always use the right spark plug. Manufacturers' spend a great deal of time choosing the right spark plug for their engine.
8. A vehicle with an eight-cylinder engine and a manual transmission has a knocking sound at the back of the engine whenever the engine is running. Which of the following is causing this noise?
- A. A worn timing belt.
- B. A loose harmonic balancer.
- C. Loose flywheel bolts.
- D. A faulty power steering pump.
Answer A is wrong. A loose and worn timing belt makes a flapping sound at the front of the engine.
Answer B is wrong. A loose harmonic balancer makes a knocking noise a the front of the engine.
Answer C is correct. Manual transmissions have flywheels that absorb engine pulses transferred through the crankshaft. Loose flywheel (manual transmission) or flexplate (automatic transmission) bolts make a knocking noise at the back of the engine whenever the engine is running.
Answer D is wrong. A faulty power steering pump makes a moaning or whining noise at the front of the engine that gets louder during turns.
9. The oil pressure switch on an engine may be faulty. All of the following are true about oil pressure switches EXCEPT:
- A. Test this switch with a digital multimeter.
- B. The warning lamp turns off as oil pressure rises.
- C. This sensor is a variable resistor.
- D. Set the meter to Ohms to check for continuity.
Answer A is wrong. Use a digital multimeter set to Ohms. They can be tested for operation with the engine not running and then with the engine running.
Answer B is wrong. Oil pressure switches are usually normally closed switches; this is why the oil pressure warning light illuminates when the ignition is first turned on and goes out after the engine starts and oil pressure rises.
Answer C is correct. The switch contacts are either open or closed; variable resistors have many positions.
Answer D is wrong. Set the meter to Ohms to check for continuity.
10. During a cylinder leakage test, a hissing sound is heard coming from the throttle body. This sound indicates:
- A. The engine has a bad exhaust valve.
- B. The engine has worn piston rings.
- C. The engine has a bad intake valve.
- D.The engine has a leaking head gasket.
Answer A is wrong. A hissing sound from the tailpipe indicates a leaking exhaust valve or seat. The exhaust valve leads to the exhaust manifold /tailpipe.
Answer B is wrong. If air is escaping through the PCV outlet, the piston rings are faulty.
Answer C is correct. A leaking intake valve will result in a hissing sound from the throttle body. It can be heard by removing the air tube and opening the throttle plate. The intake valve is leaking air into the intake manifold.
Answer D is wrong. A faulty head gasket or a crack in the blocks deck area or cylinder head allows compression to leak into the coolant jacket. It results in air bubbles appearing in the radiator neck. It can be heard by removing the air tube and opening the throttle plate. The intake valve is leaking air into the intake manifold.