A: General Engine Diagnosis; Tasks
1-9
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.
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.
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.
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.
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
