The phenomenon, causes and troubleshooting of overspeed fault of diesel engine, such as the sudden increase of engine speed, out of control over the rated speed, a huge roar, and a lot of black smoke or blue smoke from the exhaust pipe. Cause of failure: (1) The governor of the fuel injection pump itself failed, which made it lose its normal speed regulation characteristics. The characteristic of this situation is that the governor of fuel injection pump is stuck and loose. (2) The external factors change the speed regulation characteristics of the diesel engine, which shows that there is no fault in the governor of the fuel injection pump itself, and extra oil enters the cylinder to participate in combustion during the operation of the diesel engine. Troubleshooting, such as repairing the fuel injection pump and regulator, mainly check whether the fuel quantity adjusting mechanism of the fuel injection pump and the governor rod are stuck and whether the governor spring is broken. Check whether there is excess oil entering the combustion chamber for combustion, such as oil leakage from cylinder, excessive oil leakage from oil-bath air filter and oil leakage from waste gas wheel supercharger. Emergency measures for diesel engine overspeed. The overspeed of diesel engine is very dangerous, so measures should be taken in time to avoid accidents. The emergency measures to stop overspeed are as follows: quickly retract the accelerator pedal to the parking position. The fuel injection pump with exposed oil supply pull rod or toothed rod can quickly pull the pull rod back to the oil stop position. If there is a decompression device, quickly pull the decompression handle to the decompression position. Shift to the high gear in time, press the brake pedal, slowly lift the clutch and let the engine stall. Quickly loosen the high-pressure oil pipe of each cylinder and stop oil supply. If the intake pipe has a valve, the valve can be closed. If there is no valve, you can remove the air filter and block the intake pipe. Troubleshooting. Check whether the fuel control mechanism on the accelerator pedal and governor is reset. If not, repair the control mechanism.