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Delphi-Common Rail System – Controlling the fuel pressure

2 High pressure pump
3 High-pressure chamber
4 Fuel supply
5 Fuel metering valve
6 Fuel pressure sensor
7 Fuel rail
8 Solenoid valve
9 Injector needle

The engine management system on the common rail injection system is capable of providing the optimum injection pressure for each operating condition.

Fuel is compressed via the high-pressure chamber of the common rail high-pressure pump and supplied to the fuel rail.

In the process, the delivery quantity is regulated by the fuel metering valve by varying the opening cross section of the fuel metering valve accordingly.

The fuel pressure is regulated in such a way that the optimum pressure is available for each operating condition.

On the one hand, this reduces the noise emission during fuel combustion.

On the other hand, the engine management system can meter the fuel very precisely, which has a positive effect on exhaust emissions and fuel consumption.

The fuel pressure sensor continually informs the IDM (two-module system) or the PCM (single-module system) about the current fuel pressure.

Pressure is regulated via the fuel metering valve by reducing or enlarging the cross section of this valve accordingly. This means that a smaller or larger fuel quantity is supplied by the high-pressure pump until the desired fuel pressure has been reached.

• The fuel pressure depends on engine speed and engine load. Depending on the engine load requirements specified by the driver, it is possible for the maximum fuel pressure to be available at an engine speed of just 1500 rpm (depending on the vehicle).

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