Question 64

The Correct Answer is C. ### Explanation of Correct Option (C) **C) It transmits the control rack setting to the plunger.** The plunger flange labeled "A" (often integrated with the control sleeve) is the mechanical linkage point between the external control system and the internal plunger assembly. The control rack moves linearly based on the throttle or governor setting. This linear motion is converted into a rotational movement of the control sleeve and the attached flange "A." Since the plunger is locked to flange "A," the rotation changes the alignment of the plunger's helix (scroll) relative to the spill port in the barrel. This rotation is essential for changing the effective stroke, thereby determining the amount of fuel injected per cycle. Therefore, the flange transmits the setting from the control rack to the plunger. ### Explanation of Incorrect Options **A) It prevents the plunger from rotating in the barrel.** The flange "A" is designed specifically to *cause* the plunger to rotate (via input from the control rack) in order to meter the fuel. Preventing rotation would make metering impossible. **B) It takes the plunger off stroke when injection is completed.** Injection completion (spill) is dictated by the interaction between the edge of the metering helix on the plunger and the spill port on the barrel. This is an internal hydraulic function determined by the position of the plunger, not an external function of the flange "A." **D) It limits the actual stroke of the plunger.** The actual physical stroke (the total distance the plunger travels up and down) is determined by the lift of the camshaft lobe and the travel limits of the tappet assembly. The flange "A" controls the *effective* stroke (fuel metering), but it does not limit the maximum physical distance the plunger travels.