Question 52 MODE01 - Chief MODU Engineer

The Correct Answer is D **Why option D ("injection pump fuel rack binding or sticking") is correct:** The fuel rack in a mechanical diesel injection pump controls the amount of fuel delivered to the engine by moving the pump plungers. If this rack binds, sticks, or moves erratically (i.e., due to friction or a mechanical obstruction), the engine's fuel supply will fluctuate rapidly and inconsistently. This rapid, uncontrolled fluctuation in fuel delivery directly causes the engine speed to rise and fall dramatically, which is precisely defined as surging. **Why the other options are incorrect:** **A) low compression:** Low compression primarily leads to difficulty starting (especially when cold), excessive smoke, and a significant loss of power, usually manifesting as rough running or a constant misfire, but not typically the cyclical speed changes characteristic of surging. **B) solenoid stuck open:** This refers typically to the fuel shut-off solenoid or a similar control solenoid. If the fuel shut-off solenoid is stuck open, it allows fuel flow normally. If a timing or governor control solenoid were stuck open (or in any single position), it would cause stable but potentially incorrect running (e.g., poor power or rough idling), but not the oscillation of speed defined as surging, which requires an underlying cyclical control problem. **C) fuel booster pump pressure too high:** The booster (or lift) pump supplies fuel from the tank to the injection pump. While excessively high pressure can potentially overload seals or cause operational issues in the injection pump's inlet gallery, the injection pump's internal pressure regulators usually manage this feed pressure. High feed pressure typically does not cause the erratic, cyclic changes in fuel delivery necessary to produce surging.