ASE A1 Engine Repair Practice Test
6. 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.
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.
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 these could be the cause?
- 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.