The maintenance technicians disassembled the 0R-0471 injectors and found that the valve seat was severely worn, and the sealing performance between the valve seat and the needle valve was poor, leading to oil leakage. The reason for the wear was that the injectors had been used for a long time without regular maintenance, and the impurities in the fuel caused abrasive wear of the valve seat. In addition, the injection pressure was too high, which also accelerated the wear of the valve seat.