How Piston Fuel Pumps Work

When the high pressure pump camshaft 1 turns, push the gear 2 up. The movement of the rod is transmitted to the piston 8 via the lever 9. At this point, the fuel pressure above the piston increases and the pressure below the piston decreases. The intake valve 6 is closed, the valve 4 is withdrawn, half of the fuel in the upper piston chamber is pushed out, and the rest is sent to the lower piston chamber. When piston 8 descends due to restoring force

The spring 5 is opened, the intake valve is opened, the fuel enters the upper piston chamber, the injection valve 4 is closed, the fuel in the lower piston chamber is partially discharged, and the remaining feces are discharged through port 3. The pumping process is repeated in this way. In order to ensure the flow of the high-pressure pump, the fuel supply of the positive displacement pump must be much larger (about 2.5 times) than the fuel consumed by the engine.

During the operation of the pump at discharge port 3, the fuel pressure increases, spring 5 cannot overcome the fuel demand and lifts piston 8 over the entire stroke length. The spring tells the piston to move a portion of the stroke corresponding to the amount of fuel needed to run the engine. The smaller the amount of fuel required to operate the engine, the smaller the working stroke of the piston 8.