What are the causes of abnormal rail pressure?
2 Answers
Abnormal rail pressure can be caused by: faulty pressure switch or clogged oil passage. Faulty pressure switch: The engine uses high-pressure common rail injection to control fuel supply, meaning the injectors for all cylinders are supplied with high-pressure diesel through a single high-pressure fuel rail. When the fuel in the rail becomes insufficient due to reasons such as pressure issues, it leads to reduced engine power output per unit time and abnormal rail pressure. In this case, the pressure switch needs inspection and repair. Clogged oil passage: As engine oil passes through the fine pores of the oil filter, solid particles and viscous substances in the oil accumulate in the filter. If the filter becomes clogged, oil cannot flow smoothly through the filter element, potentially rupturing the filter or opening the safety valve, allowing oil to bypass through the relief valve and carry contaminants back to lubrication points. Airborne pollutants may deposit around the PCV valve, potentially clogging it. If the PCV valve is blocked, contaminated gases flow backward into the air cleaner, polluting the filter element and reducing its filtration capacity. This leads to intake of excessively dirty air-fuel mixture, further contaminating the crankcase, increasing fuel consumption, and causing abnormal rail pressure. In this case, the oil passage needs inspection and cleaning.
I often tinker with diesel cars myself and have encountered rail pressure abnormalities several times. The issues are mostly due to high-pressure fuel pump wear causing unstable fuel supply, or injector clogging leading to poor fuel flow; faulty sensors giving false pressure readings; dirty fuel filters clogging the system with impurities; aging circuits causing signal interruptions; or incorrect settings in the control computer. Last time, I used an OBD tool to check the fault codes and found the fuel pump was failing, so I replaced it myself to solve the problem. Regularly changing filters and using good quality fuel can prevent issues. Address power loss early to avoid expensive roadside breakdowns. Diesel cars are relatively low-maintenance, and keeping some tools handy for DIY repairs really saves money. Now my car runs much smoother.
