High Pressure Fuel Pump
| ITEM | DESCRIPTION |
|---|---|
| 1 | Pressure Relief Valve (PRV) |
| 2 | HP fuel line connection |
| 3 | Check valve |
| 4 | Pump plunger |
| 5 | LP fuel line connection |
| 6 | Damper chamber |
| 7 | Fuel metering valve |
In addition to the plunger, the HP fuel pump contains:
- A damper chamber
- A fuel metering valve
- A check valve
- A Pressure Relief Valve (PRV).
The damper absorbs pressure pulses from the LP fuel system. The fuel metering valve regulates the output pressure from the HP fuel pump. The fuel metering valve is a normally open solenoid valve controlled by the PCM with a PWM signal. During the inlet stroke of the plunger the fuel metering valve is de-energized, and fuel flows into the pumping chamber. The PCM energizes the fuel metering valve closed during the delivery stroke of the plunger. The pressurized fuel in the pumping chamber flows through the check valve into the fuel rail through the HP fuel line.
By changing the closing point of the fuel metering valve, the PCM can determine the volume of fuel output during the delivery stroke, and thus the fuel pressure in the fuel rail. The check valve prevents the return of HP fuel to the pumping chamber during the inlet stroke of the plunger.
The Pressure Relief Valve (PRV) protects the HP side of the system from excessive pressure if there is a failure of the fuel metering valve. If the HP fuel pump delivery pressure increases to 298 bar (4, 322 psi), the PRV opens and returns fuel to the inlet side of the plunger.
The PCM controls the output from the HP fuel pump to deliver the required volume of fuel at pressures up to 250 bar (3, 626 psi).
The PCM compares the fuel temperature information from the FRPT sensor to the data in the maps. Using this information the PCM adjusts the time the fuel injectors need to be energized to deliver the correct mass of fuel to the combustion chambers.