1. When shutting down, the speed gradually decreases, and there is no abnormal change in the sound and smoke color of the diesel engine. This fault often occurs in the fuel system. According to the principle of starting with the easy and then the difficult, first check whether there is fuel in the fuel tank and whether the fuel tank vent is blocked. If there is no oil in the fuel tank, it cannot be supplied, the vent is blocked, and negative pressure is formed in the fuel tank, then the fuel supply is not smooth. If there is no problem, then check from the low-pressure oil circuit to the high-pressure oil circuit step by step to see if there is any debris blocking the oil circuit and whether air enters. For single-cylinder engines, the failure of the high-pressure oil circuit is mostly due to the injection pump not being able to supply high-pressure oil or the injector needle valve pair being stuck; for multi-cylinder engines, it is mostly in the power transmission part of the ejection pump, such as the transmission gear rolling key, the spline key fixing screw falling off or breaking, the axle breaking, etc.
2. The speed is unstable when shutting down, and white smoke comes out of the exhaust pipe. This fault is mostly caused by water in the diesel. If the exhaust pipe still emits white smoke and the engine stalls after the water in the oil is removed, it may be caused by the cylinder gasket being burned and connected to the water channel, causing water to enter the cylinder. If the cylinder gasket is intact, it may be caused by a crack or break in the cylinder liner, or a crack in the cylinder head connected to the water channel, causing cooling water to enter the cylinder. Because there is water in the cylinder, the temperature of the mixed gas is reduced, and the engine will stall naturally.