Question 19 QMED03 - Oiler

The Correct Answer is B **Explanation for Option B (The Overrunning Clutch):** The overrunning clutch (often called a Bendix drive or similar mechanism in electric starters, or specifically designed for hydraulic starters) is a mechanical device designed precisely for the purpose of decoupling the starter drive gear from the engine's flywheel once the engine starts and exceeds the rotational speed of the starter motor. When the engine fires and its RPM increases rapidly, the flywheel begins to drive the starter gear faster than the starter motor is driving it. The overrunning clutch immediately releases, preventing the engine's high speed from damaging the starter motor, pump, or hydraulic components by driving them too fast. **Why the Other Options are Incorrect:** * **A) the immediate increase in hydraulic pressure:** While hydraulic pressure is necessary to operate the starter, an *increase* in pressure does not mechanically disengage the starter gear from the flywheel. In fact, sustained high pressure is what keeps the starter engaged until the clutch mechanism separates the drive. * **C) closing the starting check valves:** Check valves control the flow of hydraulic fluid (preventing backflow or ensuring pressure stays high in the accumulator), but they do not provide the mechanical protection needed to decouple the rotating gears. The starter drive remains engaged with the engine until a mechanical component disengages it. * **D) the pivoting of the shaft from being engaged with the flywheel:** While the starter drive gear *does* need to disengage from the flywheel, the physical mechanism that ensures this happens immediately upon startup and protects the components from high rotational speed is the overrunning clutch, not simply the physical pivoting motion itself. The overrunning clutch allows for immediate mechanical decoupling even if the starter solenoid/valve has not yet retracted the drive gear.