ABYC Diesel Practice Exam

What controls the amount of fuel delivered by each pumping element to the nozzles on pumps?

1. The fuel filter condition

2. Effective stroke of the plunger

3. Injector nozzle size

4. Fuel pump pressure

The correct answer is: Effective stroke of the plunger

The effective stroke of the plunger is integral to controlling the amount of fuel delivered by each pumping element to the nozzles in diesel fuel pumps. The plunger's stroke determines the volume of fuel that is displaced with each cycle. A longer or more effective stroke results in a greater displacement of fuel, meaning more fuel is pushed through to the nozzle. This is crucial for optimizing the engine's performance because the amount of fuel injected directly affects combustion efficiency and power output. Every time the plunger moves within the pump, it creates a suction that draws in fuel and then pushes it out to the injector nozzles. Adjustments or variations in the plunger's stroke can therefore be used to regulate fuel delivery according to the engine's demands, such as during acceleration or under load conditions. This precise control over the plunger's movement is fundamental to the proper functioning of diesel engine fuel injection systems.