Fuel rail (common rail)

fig 1 36 Fuel rail (common rail)

A Fuel fuel injection supply manifold (rail type)
B Fuel fuel injection supply manifold (spherical type)
1 Fuel pressure sensor
2 Fuel rail
3 Line connection (to the fuel injector)
4 Line connection (from the high-pressure pump)

Structure and task

The fuel rail is made of forged steel. Depending on the engine design and availability of space, a fuel rail can be long or spherical.

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

Pressure fluctuations can arise in the high pressure fuel system caused by movements in the high pressure chamber of the high pressure pump when operating and by the opening and closing of the solenoid valves at the fuel injectors.

The fuel rail is designed in such a way that its volume is sufficient, on the one hand, to minimize pressure fluctuations.

On the other hand, the volume in the fuel rail is small enough to build up the required fuel pressure time for a quick start in the shortest possible.


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.

The pressure sensor on the fuel rail informs the IDM/PCM about the current fuel pressure in the fuel rail.

Fuel pressure sensor

So that the engine management system can determine the injected fuel quantity precisely, as a function of current fuel pressure in the fuel rail, a fuel pressure sensor is located on this fuel rail.

03. August 2018 by sam
Categories: Fuel System | Leave a comment

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