ASE Certification Practice Tests

6.

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.

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.

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.

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.

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.