Question 68 MODE01 - Chief MODU Engineer

The Correct Answer is D **Why option D ("carefully check for binding in the governor linkage") is correct:** Hunting in a diesel engine governor is a cyclical oscillation of speed (too fast, then too slow, and repeating). It occurs because the governor is either too sensitive (over-correcting) or there is a mechanical delay preventing timely correction. The problem statement indicates that the most common fluid-related fixes (changing/flushing the oil and adjusting the compensation needle valve, which controls temporary droop/stability) have already been attempted without success. This strongly shifts the diagnostic focus away from hydraulic issues and towards mechanical issues. Binding or excessive friction in the external linkage connecting the governor output shaft to the fuel rack/lever (or friction within the governor's internal mechanism itself) causes a delay in the fuel pump's response to the governor's commands. This delay is a classic cause of sustained hunting, as the engine overshoots the desired speed while waiting for the friction to be overcome, and then over-corrects when the binding finally releases. **Why the other options are incorrect:** * **A) set the speed droop adjustment to zero:** Setting the speed droop (or permanent droop) to zero makes the governor isochronous (maintaining the exact same speed regardless of load). While zero droop is desirable for some applications, attempting this adjustment when hunting is already occurring will almost certainly **worsen** the hunting. Zero droop reduces system stability and increases sensitivity to load changes, making the governor highly unstable if other tuning or mechanical problems exist. * **B) check air intake manifold pressure:** Air intake manifold pressure (boost pressure) primarily affects the engine's power output and combustion efficiency. While severe, sudden changes in boost could cause temporary speed instability, it is not the root cause of sustained, consistent hunting in the governing system itself, especially after hydraulic adjustments have failed. Governor linkage is a much more direct and common mechanical culprit. * **C) calibrate the fuel pump rack settings:** The calibration of the individual fuel pump racks ensures equal fuel distribution among cylinders, necessary for smooth running and achieving maximum power. While incorrect calibration can cause uneven loading or low power, it does not typically cause the repetitive, cyclical speed oscillation defined as hunting, which is a system-wide stability failure managed by the governor.