ASE A1 Engine Repair Practice Test

6.

Spark plug tip damgage to the center electrode's ceramic insulator.

The spark plug in the illustration was removed from an engine with a dead cylinder. It has worn electrodes and the ceramic is cracked and damaged. Which of the following has caused this premature failure?

  • A. An oil control problem.
  • B. A leaking fuel injector.
  • C. A leaking intake manifold gasket.
  • D. Detonation.

6.

Answer A is wrong. Black carbon deposits indicate an oil control problem. Sometimes the tip is wet with oil.

Answer B 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.

Answer C is wrong. White carbon deposits around the electrodes and tip indicate a lean fuel condition.

Answer D is correct. Damage to the white electrode insulator indicates detonation. This happens when excessive heat and pressure in the combustion chamber cause the air/fuel charge to ignite on its own. The engine itself can also suffer damage from the unwanted detonation.

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7. Two technicians are discussing an engine that suffers from repeated spark plug failure. Technician A says a hot spark plug with too high of a heat range may result in detonation. Technician B says a cold spark plug with too low of a heat range may foul prematurely. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

7.

Answer A is wrong. Spark plugs have different heat ranges.

Answer B is wrong. A spark plug must be hot enough to prevent fouling, yet cool enough to prevent preignition or detonation.

Answer C is correct. A hot plug self cleans better, but a cold plug is better at preventing preignition. Preignition is when the air/fuel charge has burned too soon and detonation is when the air/fuel charge is burned too fast. Manufacturers’ spend a great deal of time choosing the right spark plug for their engine.

Answer D is wrong. Both technicians are correct.

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8. A light truck with a DOHC V6 engine and a manual transmission is making a rattling noise at idle, near the bottom rear end of the engine. This noise increases with engine speed. Technician A says the flywheel bolts may be loose. Technician B says this noise is likely caused by hydraulic lifter leak down. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

8.

Answer A is correct. Loose flywheel bolts make a rattling or knocking sound heard towards the bottom rear of the engine.

Answer B is wrong. This is a dual overhead camshaft engine. Hydraulic lifter leak down occurs when first starting the engine. The lifter makes a rapping noise because it’s bottoming out; not yet cushioned by engine oil pressure. This noise usually goes away after the engine runs and oil pressure is restored to the lifter.

Answer C is wrong. Only technician A is correct. Loose flywheel bolts can be heard toward the bottom rear of the engine where it’s joined to the transmission’s bellhousing.

Answer D is wrong. Technician A is correct.

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9. An oil pressure switch is being tested for operation. Technician A says to use a digital multimeter. Technician B says this switch can be tested on the vehicle. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

9.

Answer A is wrong. Use a digital multimeter set to Ohms.

Answer B is wrong. They can be tested for operation with the engine not running and then with the engine running.

Answer C is correct. They are often 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 D is wrong. Both technicians are correct.

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10. During a cylinder leakage test air bubbles appear in the neck of the radiator. Technician A says a faulty intake valve will cause this condition. Technician B says a crack in the engine block will cause this condition. Who is correct?

  • A. Technician A
  • B. Technician B
  • C. Both A and B
  • D. Neither A or B

10.

Answer A is wrong. 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. This is because the intake valve is leaking air into the intake manifold.

Answer B is correct. A crack in the blocks deck area or cylinder head allows compression to leak into the coolant jacket. This results in air bubbles appearing in the radiator neck.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.

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