High Pressure, High Performance

How to prevent common faults in rail systems

CARWOOD elaborates on the most common causes for failure found in common rail systems and how to prevent them.

Common rail systems consist of a shared high-pressure reservoir (common rail) that supplies all the cylinders with fuel. Considered as the heart of the fuel system, this is where diesel fuel pressure increases. Unlike conventional diesel injection systems where fuel pressure has to be generated individually with each injection, common rail systems generate pressure separately from injections, allowing fuel to constantly be available at the required pressure for injection.


By constantly feeding fuel to the common rail, the high-pressure pump maintains system pressure that keeps fuel readily available even at low engine speeds. This is because the pressure generation is not reliant on the engine speed.

Most common rail systems today are equipped with radial piston pumps. These are typically favoured for their improved efficiency, producing high pressures and low noise levels.


Carwood is the approved diesel remanufacturer for OE diesel systems such as Bosch, Denso, VDO and Delphi. Whilst the construction of common rail pumps may differ slightly between each manufacturer, the most common causes for fuel pump failures are:

  • Inadequate filtration and poor filter quality
  • Filter service life exceeded
  • Internal parts are corroded and contaminated
  • Water contamination

In order to prevent these issues that can lead to failure of the pump, it is essential for installers to observe the best practices whilst servicing these powerful, yet delicate systems.

The quality of fuel and filtration is critical to the overall performance of common rail systems. Inadequate fuel quality and filtration can lead to the contamination and corrosion of the pump interior.

Carwood advises that installers should always maintain recommended service intervals and use OE quality filters when replacements are necessary. Vehicle owners should also ensure that they are using the correct fuel grade (EN590).

Diesel Pump Fault Identification-Rail Systems


Due to the fine tolerances that they work in, the latest common rail systems have proven to improve performance with quieter engines, lower fuel consumption and reduced emissions. All remanufactured parts within the FPS common rail range by Carwood only use OE quality component parts and adhere to OE repair processes. In addition to performing a ‘plug-in diagnostic’, it is also important for installers to perform a mechanical pressure test (false actuator test) to check the pressure control valve control.


Carwood and FPS recently created a fault diagnosis guide. With comprehensive key points and easy-to-follow action charts, the guide provides systematic steps to help service common rail diesel systems effectively, efficiently and safely.

Carwood also offers product support with a dedicated technical helpline that can be reached at 0844 876 2524. Catalogued on the F:Drive and MAM Autocat, Carwood remanufactured common rail parts are available from FPS via same/next-day delivery. Speak to your local FPS representative for more information.


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