ASE A1 Engine Repair Practice Test

61. 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.

61.

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 engine oil, the engine has a bad valve, typically the exhaust 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.

62. 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.

62.

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.

63. Technician A piston pin offset locates the piston pin slightly closer to the thrust side of the engine. Technician B says piston side thrust mainly occurs during the power stroke. Who is correct?

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

63.

Answer A is wrong. Piston pin offset pushes the major thrust side tighter against the engine, affecting the connecting rod's angle, reducing piston slap, and providing efficient, quieter engine performance.

Answer B is wrong. During the power stroke, the force of combustion on the piston's dome and the connecting rod angle force the piston's thrust side against the cylinder wall.

Answer C is correct. Both Technicians are correct.

Answer D is wrong. Both Technicians are correct.

64. Technician A says a bent connecting rod results in excessive piston skirt wear. Technician B says a bent connecting rod can result in low cylinder compression. Who is correct?

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

64.

Answer A is wrong. Typically a bent rod is caused by overrevving, detonation, or fluid entering the cylinder ending in a hydrolocked engine.

Answer B is wrong. A slightly bent connecting rod may not be noticeable during the initial inspection. However, it may appear as one-sided diagonal wear on the skirt located on the thrust side of the piston.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.

65. Technician A says VVT variable valve timing controls valve timing independent of crankshaft rotation. Technician B says thick contaminated oil will drastically affect the operation of a VVT engine. Who is correct?

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

65.

Answer A is wrong. Today's engines have tight tolerances and typically use a different, lighter oil viscosity than older engines.

Answer B is wrong. Unchanged contaminated oil causes problems with VVT systems. It clogs the control valve, screen, and passages in the camshaft resulting in system failure.

Answer C is correct. Both technicians are correct.

Answer D is wrong. Both technicians are correct.