1. Improper fuel injection pump assembly
Why?
1) When assembling the fuel injection pump of a diesel engine, if the sleeve positioning screw is not screwed into the sleeve positioning groove, the sleeve will rotate when the diesel engine is running, thereby changing the relative position of the spiral groove on the plunger of the fuel injection pump and the oil return port on the sleeve. When the throttle control handle is pulled to the flameout position, the straight groove on the plunger cannot be aligned with the oil return port on the sleeve, which will cause the fuel injection pump to be unable to stop pumping oil and the diesel engine to be unable to be turned off.
2) When assembling the fuel injection pump, if the marks of the three parts of the rack, gear, and plunger are not aligned or are not assembled according to regulations, when the throttle control handle is pulled to the flameout position, the straight groove on the plunger cannot be aligned with the oil return port on the sleeve, and the fuel injection pump cannot stop pumping oil, causing the diesel engine to be unable to be turned off.
2. Exhaust brake device malfunctioning
For vehicles equipped with exhaust brakes, the diesel engine is turned off with the help of the exhaust brake. When the engine is to be turned off, the driver steps on the exhaust brake button valve, and the exhaust brake butterfly valve power cylinder works after ventilation, the butterfly valve core rotates, and the exhaust pipe is blocked. At the same time, when the exhaust brake button valve is stepped on, the oil stop cylinder moves and the oil volume is closed to the minimum position to achieve the purpose of turning off the engine.
The main reasons for the failure to turn off the engine when operating in the correct way are as follows:
1) It is a failure of the exhaust brake button valve. Leakage or pipeline rupture and no ventilation cause the power cylinder of the butterfly valve to not work, so the butterfly valve core cannot rotate and block the exhaust pipe; the oil stop cylinder is not ventilated or leaks, the oil volume is still at a certain position, and the engine cannot be turned off.
2) It is a failure of the exhaust brake butterfly valve power cylinder. If the exhaust brake butterfly valve power cylinder leaks or does not work, although the exhaust brake button valve is stepped on, due to the leakage of the power cylinder, the piston stroke is not large, and the exhaust pipe cannot be blocked, so it cannot be turned off.
3) The linkage mechanism between the exhaust brake butterfly valve and the power cylinder is loose. At this time, although the power cylinder is in motion, it cannot block the exhaust pipe, making it difficult to shut down the engine.
4) The injection pump plunger is stuck and the plunger spring is broken. At this time, although the oil stop cylinder is in motion, it cannot pull the throttle adjustment lever, causing the engine to rotate at a certain speed and cannot be shut down.
What to do?
If this happens, if the button valve or oil stop cylinder is faulty, it should be replaced; if the butterfly valve power cylinder is faulty, it should be repaired in time, and if it is seriously damaged, it should be replaced; if the linkage mechanism is loose, it should be tightened in time, and the pipeline should be replaced if it leaks; if the injection pump plunger is stuck, it should be repaired in time and checked on the calibration bench.
3. Diesel engine "runaway"
Diesel engine "runaway" means that the speed loses control, increases sharply, exceeds the rated speed, and is accompanied by violent vibration and abnormal noise. When the diesel engine "runs away", if it cannot be stopped in time with effective methods, it will cause major property losses or even casualties.
The main reasons for the "runaway" of the diesel engine are the following two aspects:
One is that a large amount of oil enters the cylinder to burn; the other is oversupply of fuel. Although the performance is that the engine is overspeeding, there are also differences. A large amount of oil enters the cylinder to burn, and the exhaust pipe emits blue smoke; when the "runaway" is caused by oversupply of fuel, the exhaust pipe emits thick black smoke. When the diesel engine "runs away", you must respond calmly and calmly, and first judge the color of the exhaust pipe smoke.
What to do?
If blue smoke is emitted, you can block the intake pipe or open the decompression, because the method of cutting off the fuel oil line is ineffective at this time; if thick black smoke is emitted, you can cut off the fuel oil line, that is, quickly loosen the connecting nut of the high-pressure oil pipe. At the same time, block the intake pipe or open the decompression.
