Series 40E Troubleshooting – Section 4.1 Injector Operation

The injection operation is divided into three stages or cycles:‪

1. Fill stage
2. Injection stage
3. End of injection

During the fill stage, the solenoid is de-energized and the poppet valve is in the closed position preventing the flow of high pressure oil to the intensifier piston. At this point the intensifier piston is in the upper position allowing the fuel supply to enter and fill the nozzle of the injector.‪

Once the ECM commands injection, the solenoid is energized and the injection stage is initiated. Such action rapidly lifts the poppet valve from its seat, allowing the high pressure oil to enter the injector. At the intensifier piston, the pressure is transmitted from the high pressure oil to the fuel and multiplied 6 to 7 times creating fuel injection pressures of up to 21,000 lb/in.²
.‪

As the fuel pressure increases, check valves prevent the fuel from flowing back to the supply manifold. Once the pressure is high enough to lift the needle valve, high pressure fuel is atomized into the combustion chamber.‪

Once injection is completed, the ECM de-energizes the solenoid; the poppet valve and the intensifier piston return to the closed position; and the injector returns to the fill stage. See Figure
“HEUI Injector Stages of Operation”

. ‪

Figure 1. HEUI Injector Stages of Operation