Question 22 MODE02 - Assistant MODU Engineer

The Correct Answer is B **Explanation for Option B (Correct Answer):** The plunger flange, often referred to as the control sleeve or gear segment (labeled "A" in typical illustrations of diesel fuel injection pumps like MO-0061), is physically coupled to the control rack (or control rod). This flange engages with the helical or inclined control edge (the helix) on the plunger itself. When the control rack moves, it rotates the plunger flange, which in turn rotates the plunger within the barrel. This rotation is crucial because it changes the effective stroke of the injection (the amount of fuel delivered) by aligning the fuel spill port with the helix at different points in the plunger's upward travel. Therefore, its primary function is to **transmit the control rack setting (the operator's demand for fuel) to the plunger**, thus regulating the engine power. **Explanation for Incorrect Options:** * **A) It limits the actual stroke of the plunger:** The actual physical stroke (the distance the plunger travels up and down) is limited by the camshaft lobe height and the follower mechanism, not the rotating plunger flange. The flange controls the *effective* stroke (the portion of the stroke during which fuel is delivered), not the total mechanical stroke. * **C) It takes the plunger off stroke when injection is completed:** Injection is completed when the metering helix (the spill edge) uncovers the spill port/bypass port. This is an inherent function of the meter/spill helix design on the plunger body, not a direct function of the rotating flange itself. The flange dictates *when* injection starts and ends relative to the stroke, but the completion mechanism is the port being uncovered by the helix. * **D) It prevents the plunger from rotating in the barrel:** The entire function of the flange is to *cause* controlled rotation of the plunger to meter fuel. The flange *rotates* the plunger as demanded by the control rack setting.