ASE A1 Engine Repair Practice Test

66. A cylinder compression test indicates the #1 cylinder is below specifications. After injecting oil, the pressure remains the same. Which of the following could be the cause?

  • A. A hole in the piston.
  • B. A bad valve.
  • C. Worn piston rings.
  • D. A faulty head gasket.

66.

Answer A is wrong. A hole in the piston results in a significant leak and no compression in the cylinder.

Answer B is correct. This second or wet compression test increases compression if the engine has worn piston rings by increasing the seal between the rings and the cylinder wall. If there is little or no change in compression after adding oil, suspect a bad valve. A cylinder leakage test will indicate if it's an exhaust or intake valve.

Answer C is wrong. If cylinder compression increases after adding a teaspoon or two of engine oil, the piston rings have worn.

Answer D is wrong. When the other cylinders are within specifications, and two adjacent cylinders on the same bank are low, suspect a faulty head gasket.

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67. 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.

67.

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 much time choosing the right spark plug for their engines.

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68. Technician A says a blown head gasket results in coolant entering the combustion chamber. Technician B says a blown head gasket could result in contaminated engine oil. Who is correct?

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

68.

Answer A is wrong. Coolant entering the combustion chamber will vaporize, resulting in white-colored exhaust smoke.

Answer B is wrong. Coolant enters the crankcase through a blown head gasket or leaking intake manifold jacket and mixes with the oil. As a result, the oil turns milky brown. The milkshake-looking oil appears on the dipstick and accumulates around the oil and radiator fill neck.

Answer C is correct. Both Technicians are correct.

Answer D is wrong. Both Technicians are correct.

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69. Technician A says to use a feeler gauge to measure the top compression piston ring end gap. Technician B says if the piston ring end gap is too small, the ends may touch, resulting in scuffing and binding. Who is correct?

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

69.

Answer A is wrong. Use a feeler gauge to measure the top compression piston ring end gap.

Answer B is wrong. Too much piston ring end gap results in compression leaks and blowby. Too little gap results in the ends touching, causing scuffing, binding, and possible engine failure.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

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70. Technician A says returnless fuel systems have a vacuum-operated fuel pressure regulator on the fuel rail. Technician B says returnless fuel systems have no fuel return line. Who is correct?

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

70.

Answer A is wrong. The fuel pressure regulator is in the fuel tank. A faulty fuel pressure regulator, clogged fuel filter, or a weak fuel pump will cause low fuel pressure.

Answer B is correct. The control module receives a signal from the fuel pressure sensor on the fuel rail and controls the pump pressure and flow. Returnless systems have no return line, eliminating emission problems caused by warm fuel returning to the tank.

Answer C is wrong. Technician B is correct.

Answer D is wrong. Technician B is correct.

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