The maintenance technicians tested the injection pressure of the 0R-0471 injectors and found that the pressure fluctuated between 16-22MPa, which was far beyond the standard fluctuation range (≤1MPa). After disassembling the injectors, it was found that the plunger was severely worn, and the gap between the plunger and the cylinder sleeve was too large, leading to pressure leakage and unstable pressure. The reason for the wear was that the fuel filter was not replaced regularly, and the impurities in the fuel caused abrasive wear of the plunger.