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. 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.
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 high oil pressure and a ballooned oil filter.
Answer C is wrong. A clogged filter and a stuck closed oil bypass valve would result in a ballooned filter.
Answer D is correct. Each of these conditions would result in a ballooned oil filter except worn bearings. Worn engine bearings and faulty oil pumps result in low oil pressure.
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. An outside micrometer is used to check 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. Journals wear at the ends and in the middle.
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 intercooler's 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 it enters the engine's 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.