ASE A1 Engine Repair Practice Test
16. A loud squeal at the front of a supercharged V6 engine gets louder as the engine is accelerated. Which of the following is causing this noise?
- A. Chipped compressor wheel.
- B. Damaged turbine wheel.
- C. Turbine shaft needle bearings.
- D. The front roller bearings.
Answer A is wrong. A turbocharger has a compressor wheel. Superchargers contain a pair of two or three-lobed vanes that rotate as the engine turns.
Answer B is wrong. Superchargers are belt-driven and contain bearings that squeal when worn or deprived of lubricant. A turbocharger has an exhaust-driven turbine wheel.
Answer C is wrong. Turbine shaft needle bearings are part of a turbocharger.
Answer D is correct. Superchargers contain roller and needle bearings that rotate over 10,000 RPM.
17. A vehicle's engine is slow cranking. Which of the following should the technician check first?
- A. The starter.
- B. The alternator.
- C. The battery.
- D. The ignition switch.
Answer A is wrong. After the battery, inspect and test the starter circuit.
Answer B is wrong. Check the battery state of charge, capacity, and condition.
Answer C is correct. Inspect and test the battery and its connections when the starter is slow cranking or unable to turn the engine.
Answer D is wrong. Check the battery and perform voltage drop tests on the starter circuit cables and connections.
18. A vehicle with a new, fully charged battery discharges overnight. A battery state of charge test indicates 9.2 volts the next morning. Which test is used to diagnose this condition?
- A. A parasitic drain test.
- B. An alternator full-field test.
- C. A specific gravity test.
- D. A voltage drop test.
Answer A is correct. A parasitic drain test measures the current draining from the battery while the vehicle rests. Set the meter to measure amperage (ammeter) and connect the probes in series between the negative battery terminal and the negative battery post. Use this test to detect excessive current draw if the vehicle's battery drains after shutdown.
Answer B is wrong. Test the alternator's regulator with a full field test if the alternator has low output. This test bypasses the regulator, energizing the rotor with unregulated voltage. Use this test if the charging system is not sufficiently charging the battery.
Answer C is wrong. Measuring a battery's specific gravity is a way of measuring a battery's state of charge. A hydrometer measures the specific gravity of the electrolyte solution in each cell. A fully charged lead-acid battery has a specific gravity of 1.265 at 80° F.
Answer D is wrong. It's common to perform a voltage drop test on the starter circuit. A voltage drop test is the best way to find high-current circuit resistance.
19. Technician A says to use a cylinder bore gauge to measure the engine block cylinder bores for excessive taper. Technician B says to measure the cylinder bores for an out-of-round condition before installing new pistons. Who is correct?
- A. Technician A
- B. Technician B
- C. Both A and B
- D. Neither A or B
Answer A is wrong. The cylinder's taper is the difference between its top and bottom.
Answer B is wrong. Pressures exerted at the top of the ring travel, and the thrust and non-thrust surfaces take their toll over time. Measure for out-of-round and taper before reconditioning the cylinder walls.
Answer C is correct. Both technicians are correct.
Answer D is wrong. The cylinder's taper and out-of-round dictate whether it's acceptable for honing or if the cylinder needs to be bored.
20. When replacing connecting rod bearings in an engine:
- A. Replace the crankshaft if the connecting rod bearings are worn.
- B. Scratch the cylinder number on each connecting rod arm.
- C. Use oversized bearings.
- D. Do not mix connecting rods and rod caps.
Answer A is wrong. Inspect the crankshaft journals and measure end-play; replace it only if necessary. Keep the main bearing caps in order during crankshaft removal. Most main bearing caps come marked with a number and directional arrow.
Answer B is wrong. Making an indentation on a connecting rod shaft could end in catastrophe. These rods are made of durable metals and often hardened to retain their strength as the engine wears. Even scratching into a connecting rod will weaken it.
Answer C is wrong. Bearings come standard, oversized, or undersized; the size is stamped on the back of the insert. An oversized bearing has the same material thickness on the inside facing the crankshaft journal and more material on the outside facing the bore. Use an oversized bearing after the block has been line bored.
Answer D is correct. Connecting rods and caps must remain a matched set. After removal, screw the nuts onto the bolts to keep the rods and caps together for reassembly.