How to Troubleshoot Rail Pressure Fault?
2 Answers
Rail pressure fault troubleshooting method is: Turn on the ignition, connect the decoder. Use the decoder to enter the system and read the fault code. The decoder reads a current fault code 0559, indicating that the rail pressure is too low, below the normal working range. From the fault code, it can be inferred that the rail pressure sensor has detected that the fuel pressure in the common rail pipe is too low, making it difficult to establish rail pressure, resulting in difficulty starting the engine. Many reasons such as the rail pressure sensor, fuel metering unit, or clogged and flattened return pipe can cause the rail pressure relief valve to open, leading the engine control unit to enter a self-protection limp-home mode. Only a diagnostic tool can be used to confirm the issue.
Last time I encountered a rail pressure fault, I first checked the low-pressure fuel circuit and found the diesel filter was severely clogged. After replacing the filter, the problem persisted, so I plugged in the diagnostic tool to check the fault codes, which showed an error with the rail pressure sensor. I disconnected and reconnected the sensor plug, but that didn't solve the issue either. Next, I tested the fuel pressure—the low-pressure side was normal, but the high-pressure side was lower than it should be. Finally, I discovered that the intake metering valve on the high-pressure fuel pump was stuck. After cleaning the valve core, the fault was resolved. Remember, regularly replacing the diesel filter can prevent this issue. When facing a fault, don't rush to replace parts—first, troubleshoot the fuel circuit and sensors, these basic components.
