Denso-Common Rail System – Fuel rail (common rail)

1 Fuel pressure sensor
2 Pressure limiting valve
3 Fuel rail

The fuel rail performs the following functions:
• stores fuel under high pressure and
• minimizes pressure fluctuations.

Pressure fluctuations are induced in the high-pressure fuel system due to the operating movements in the high-pressure chambers of the high-pressure pump and the opening and closing of the solenoid valves on the fuel injectors.

Consequently, the fuel rail is designed in such a way that, on the one hand, it possesses sufficient volume to minimize pressure fluctuations, but, on the other hand, the volume in the fuel rail is sufficiently low to build up the fuel pressure required for a quick start in the shortest time possible.

Function

The fuel supplied by the high pressure pump passes through a high pressure line to the high pressure accumulator. The fuel is then sent to the individual fuel injectors via the four injector tubes which are all the same length.

When fuel is taken from the fuel rail for an injection process, the pressure in the fuel rail is kept almost constant.

Pressure limiting valve

The pressure limiting valve opens at a fuel pressure of approx. 2000 bar. It serves as a safety device in the case of malfunctions in the high-pressure system. Thus, damage due to excessive pressure in the high-pressure system is prevented.

The pressure limiting valve operates as a disposable valve. This means that it must be replaced after a single triggering, as the valve can no longer be guaranteed leak-free.

Triggering of the pressure limiting valve is detected by the PCM, whereupon a corresponding DTC is set and the MIL is actuated.

For removal and installation, please follow the instructions in the current service literature.

01. June 2019 by Ron
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