Diesel Common Rail Fuel systems

Most Modern Diesel Fueled vehicles now use a ‘Common Rail’ Fuel Injection system. These systems were first produced in the mid to late 90’s, and now nearly every new vehicle is fitted with this type of system. There are four main companies that design and make these systems for the car manufacturers, Bosch, and Delphi, being the most popular.

The system comprises of a low pressure lift pump which lifts the diesel fuel from the tank, via a filter, Which then gets transferred to a high pressure pump. The fuel then gets pressurised up to 1950 bar (29’000 psi), then gets transferred to the fuel rail. Fuel pressure is monitored by an electronic control unit and regulated by a solenoid valve which can be mounted in either the high pressure pump or fuel rail. Injectors are then fed from the rail and controlled electronically  by the engine control module to give the correct injection sequence for that current engine condition. Fuel that has back leaked past the injectors internal workings or has not been required in the rail or pump is then returned back to the fuel tank for reuse. On some systems a fuel cooler is fitted on this return line.

Injectors on these systems are made to a very tight tolerance some parts on the injector have a tolerance of 2 microns in the machined parts, these can also can carry out over 200 precise  injection sequences in the blink of an eye. With this in mind these are very delicate pieces of equipment, and extremely susceptible to dirt or water ingress.

At R M Motors we can diagnose faults on these vehicles and work out a  suitable remedy, If injectors require replacement we can code them to the vehicle using our diagnostic equipment.

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