These Three Faults Occur Frequently in Diesel Common Rail Systems. How to Eliminate Them?

In the maintenance of high-pressure common rail systems, high-pressure oil circuit failure is a relatively common problem. Failure of the high-pressure oil circuit may result in failure to start, difficulty in starting, and stalling during operation. These are fault phenomena that often trouble maintenance personnel.

The Fuel Injector Doesn’t Inject Fuel


When the injector fails to inject fuel, symptoms such as large idle speed jitter and no pulsation in the high-pressure oil pipe will usually appear. At the same time, when a fault diagnosis instrument is used for detection, it may display information such as increased idle speed oil volume and fuel injection drive circuit failure.


1. First, check whether there is any problem with the injection drive circuit, whether it is damaged, whether there is a short circuit or open circuit failure.

2. Check the high-pressure oil pipe for leaks.

3. Check whether the fuel injector itself is faulty, such as excessive carbon deposits causing sticking, or the fuel injector has failed.

Rail Pressure is Difficult to Establish

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When a fault occurs that the rail pressure is difficult to establish, using a diagnostic instrument to detect the fault will obtain information about the rail pressure being too low. This is usually caused by problems such as insufficient fuel supply capacity of the high-pressure pump, failure of the fuel metering valve, or loose sealing of the high-pressure pipeline connection.


1. Check whether the high-pressure oil pump can provide sufficient rail pressure.

2. If the high-pressure fuel pump is normal, check whether the fuel metering valve is faulty.

3. Check whether the indentation on the sealing surface at the connection between the high-pressure connecting pipe and the injector is regular.

Rail Pressure Continues to be Extremely High

640 (2)

When this fault occurs, the fault diagnostic tool can be used to detect that the derailment pressure exceeds the limit for longer than the specified value. Common causes of this problem are metering errors and pressure limiting valve failure.


1. Check the fuel metering valve for malfunction.

2. Check whether the pressure limiting valve of the common rail system is faulty.

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