Question 49Motor Plants - 1st Asst/Chief
70% to passA four-stroke cycle auxiliary diesel engine fuel cam has shifted from its original position during maintenance. To ensure correct timing of the fuel pump, the intake and exhaust valves should be in what position when approaching top dead center for injection?
AIntake and exhaust valves closed
BExhaust valve open, intake valve closed
CIntake and exhaust valves open
DIntake valve open, exhaust closed
AI Explanation
The correct answer is A) Intake and exhaust valves closed. When the fuel cam has shifted during maintenance, the intake and exhaust valves should be in the closed position as the engine approaches top dead center for fuel injection. This ensures the correct timing of the fuel pump relative to the piston position, as the valves need to be closed to allow for proper compression and combustion of the fuel-air mixture. The other options are incorrect because: B) has the exhaust valve open, which would disrupt the compression stroke; C) has both valves open, which is the incorrect valve position for the injection timing; and D) has the intake valve open, which would also disrupt the compression stroke.
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