In the post-repair test, the diesel engine is easy to start for the first time, but it cannot be started after stopping. After inspection, the gear housing cover was removed, and it was found that the housing of the high-pressure oil pump was broken, and the locating screw of the tappet body at the rear of the pump body was cracked and fell off. The reason for the damage is that the No. 1 pump is first installed on the gear chamber cover. When the gear chamber cover is installed on the machine body, the driver does not use a screwdriver to push in the tap hole and compress the tappet and then install the gear chamber cover. The gear chamber cover is rigidly mounted on the body so that the tappet body of the No. 1 pump is abutted against the cam of the camshaft.