Question 151Motor Plants - QMED

The correct answer is C) rotation of the pump plunger. In a helical plunger fuel injection pump, the amount of fuel delivered is controlled by the rotation of the pump plunger. As the plunger rotates, the changing helical groove on the plunger varies the effective stroke of the plunger, which in turn adjusts the amount of fuel delivered. This mechanism allows for precise control of the fuel injection quantity. The other options are incorrect because they do not accurately describe the core operating principle of a helical plunger fuel injection pump. Varying the pump discharge or return pressure would not directly control the fuel delivery, and rotating the pump barrel would not achieve the same effect as rotating the plunger.