The maintenance technicians checked the 0R-3190 injectors and found that the nozzle needle valve was worn, and the sealing performance between the needle valve and the valve seat was poor, leading to oil leakage at the nozzle. In addition, the injection pressure of the injectors was too low, which also aggravated the oil leakage. The reason for the wear of the needle valve was that the company used low-quality diesel fuel, and the impurities in the fuel caused abrasive wear of the needle valve.