ASE A1 Engine Repair Practice Test
31. A spark plug's electrode is covered with thick black carbon deposits. Which of these could be the cause?
- A. The engine has a vacuum leak.
- B. This reading shows normal wear.
- C. The piston rings are worn.
- D. The fuel injector is leaking.
Answer A is wrong. White carbon deposits around the electrode indicate a lean fuel condition.
Answer B is wrong. A 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 because the 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.
32. While measuring a cylinder head's valve stem installed height, one valve tip is higher than the others. The MOST likely cause of this condition is:
- A. Worn valve springs.
- B. Valve spring installed height.
- C. A worn valve seat.
- D. Loose cylinder head bolts.
Answer A is wrong. Worn valve springs result in valve float and a misfire at high engine speeds.
Answer B is wrong. The valve spring installed height is a measurement taken from the pocket or cup where the spring sits to the underside of the retainer/rotator with the valve closed.
Answer C is correct. A worn valve face or seat is the most likely cause. Measure the valve stem installed height with a valve stem height gauge.
Answer D is wrong. Loose cylinder head bolts result in a loss of compression, overheating, and white-colored exhaust.
33. During an oil change, the technician notices that the oil filter is swollen. Which of the following is LEAST likely to result in this condition?
- A. Unchanged contaminated engine oil.
- B. A stuck closed oil pressure relief valve.
- C. A stuck closed oil filter bypass valve.
- D. Worn crankshaft bearings.
Answer A is wrong. Contaminated oil will clog the filter if the oil filter bypass valve is stuck closed. This will result in a swollen and ballooned oil filter.
Answer B is wrong. A stuck closed oil pressure relief valve would cause a ballooned oil filter.
Answer C is wrong. A stuck closed oil bypass valve would result in a ballooned oil filter. The oil filter oil bypass valve opens to prevent catastrophic oil starvation.
Answer D is correct. Each condition would result in a ballooned oil filter except for worn crankshaft bearings.
34. The measuring tool pictured above is:
- A. A dial indicator for measuring crankshaft rod journals.
- B. A micrometer for measuring main crankshaft journals.
- C. A dial indicator for measuring crankshaft endplay.
- D. A bore gauge for measuring cylinder wall thickness.
Answer A is wrong. Use an outside micrometer to measure for camshaft journal wear.
Answer B is wrong. Use an outside micrometer to check for crankshaft journal wear. Check around and along the journals for taper or out-of-round.
Answer C is correct. Measure crankshaft end play with the dial indicator's tip on the crankshaft flange. Use a pry bar or a large screwdriver to move the crankshaft back and forth.
Answer D is wrong. Answer C is correct. If there's a sharp rapping noise, especially at idle, the crankshaft should be inspected and measured for crankshaft endplay.
35. A supercharged engine is detonating during acceleration. Technician A says to check the intercooler for leaks. Technician B says to inspect the intercooler's radiator for debris. Who is correct?
- A. Technician A
- B. Technician B
- C. Both A and B
- D. Neither A or B
Answer A is wrong. Liquid-cooled intercoolers contain piping, a coolant reservoir, and a radiator.
Answer B is wrong. The intercooler's radiator, usually located at the front of the vehicle where fresh air can pass through, releases heat to the atmosphere.
Answer C is correct. The intercooler's job is to cool the compressed, heated air charge before entering the combustion chamber. This cooled charge increases the engine's horsepower and prevents harmful detonation.
Answer D is wrong. Liquid-cooled intercoolers typically require a 50/50 mixture of antifreeze to water. They are leak tested similar to the engine's cooling system.