A: General Engine Diagnosis; Tasks 1-9

5. A port fuel-injected engine has a steady "puff" noise in the exhaust with the engine idling. The cause of this problem could be: A. a burned exhaust valve - B. excessive fuel pressure - C. a restricted fuel return line - D. a sticking fuel pump check valve

A - Excessive fuel pressure or a restricted return fuel line causes a rich air-fuel ratio. Therefore B and C are incorrect. A sticking fuel pump check valve may cause hard starting so D is incorrect. A burned exhaust valve causes a "puff" noise in the exhaust.

2. A throttle body injected engine has a no-start complaint, and no fuel is discharged from the injectors when the engine is cranking. Technician A says to check the voltage supply to the fuel pump. Technician B says to check the fuel filter for a partial restriction. Who is correct? A. A only - B. B only - C. Both - D. Neither

A - Technician B is incorrect because with a partially restricted fuel filter, some fuel is still discharged from the injectors. Technician A is correct because if there is no voltage supplied to the fuel pump, the fuel pressure is zero, and no fuel is discharged from the injectors.

9. During a leakage test, cylinder number 2 has 50-precent leakage and air is escaping from the pcv valve opening. Technician A says that the intake valve in the number 2 cylinder may be leaking. Technician B says that the rings in the number 2 cylinder may be worn. Who is correct? A. A only - B. B only - C. Both - D. Neither

B - A leaking intake valve causes air to escape from the air intake. Therefore A is incorrect. Worn rings cause air to escape from the PCV valve opening during the cylinder leakage test.

8. During a compression test, a cylinder has 40 percent of the specified compression reading. When the technician performs a wet test the compression reading on this cylinder is 75 percent of the specified reading. The cause of the low compression reading could be: A. A burned exhaust valve - B. worn piston rings - C. a bent intake valve - D. a worn camshaft lobe

B - If the compression increases significantly during a wet test, worn rings and cylinders are indicated.

1. While discurssing a basic diagnostic procedure, Technician A says that the most complicated diagnostic tests should be performed first. Technician B says that the customer complaint must be identified. Who is correct? A. A only - B. B only - C. Both - D. Neither

B - The easiest, quickest test should be performed first. The customer complaint must be identified during a basic diagnostic procedure.

4. A heavy thumping noise occurs with the engine idling, but the oil pressure is normal. This noise may be caused by: A. worn pistons and cylinders - B. loose flywheel bolts C. Worn main bearings - D. loose camshaft bearings

B - Worn pistons and cylinders would cause a rapping noise while accelerating, and worn main bearings would cause a thumping noise when the engine is started. Therefore, A and C are incorrect. Loose camshaft bearings usually do not cause a noise unless severely worn, so D is incorrect. Loose flywheel bolts may cause a thumping noise at idle.

7. During a cylinder balance test on an engine with electronic fuel injection, cylinder number 3 provides very little rpm drop. Technician A says that the ignition system may be misfiring on the number 3 cylinder. Technician B says that the engine may have an intake manifold vacuum leak. Who is correct? A. A only - B. B only - C. Both - D. Neither

C - A cylinder with very little rpm drop indicates cylinder misfiring, which may be caused by the ignition system or an intake manifold vacuum leak.

3. A cooling system is pressurized with a pressure tester to locate a coolant leak. After 15 minutes, the tester gauge has dropped from 15 psi to 5 psi, and there are no visible signs of coolant leaks in the engine compartment. Technician A says that the engine may have a leaking head fasket. Technician B says that the heater core may be leaking. Who is correct? A. A only - B. B only - C. Both - D. Neither

C - Technicians A & B because neither a leaking head fasket nor heater core will cause leaks in the engine compartment, but they will reduce the test pressure.

6. With the engine idling, a vacuum gauge connected to the intake manifold fluctuates between 12in - 18in HG. These vacuum gauge fluctuations may be caused by: A. late ignition timing - B. intake manifold vacuum leaks - C. A restricted exhaust system - D. Sticky valves

D - Late ignition timing, or an intake manifold vacuum leak, causes a low steady vacuum guage reading. Therefore A and B are incorrect. A restricted exhaust system causes a low vacuum reading at high speeds, so C is incorrect. Sticking valves cause a vacuum gauge fluctuation between 12in and 18in HG at idle.