The needle valve of the fuel injector is not tightly sealed with the valve body and is seized
Symptoms of failure: the low-pressure oil circuit is unblocked, the diesel engine is rotated after the speed control handle is placed in the oil supply position, the fuel injection sound of the fuel injector cannot be heard for some cylinders, and white smoke is emitted from the exhaust pipe, so it is difficult to catch fire. When the diesel engine is on fire, the exhaust pipe is still emitting smoke, the idling speed is not stable, accompanied by the panting sound of "Teng, Teng", and there is an obvious knocking sound at high speed and throttle. When the temperature of the diesel engine rises, the exhaust pipe emits black smoke, the fuel injector is hot, and the fire "misses legs". Disconnect the high pressure oil pipe of the missing leg cylinder. The exhaust pipe of the diesel engine no longer emits smoke, and the sound of cylinder knocking also disappears. However, there is exhaust phenomenon at the high-pressure oil pipe joint of the injector, and foam is discharged.
Failure cause analysis: (1) During the working process of the diesel engine, the high-pressure diesel oil pumped out from the fuel injection pump carries some mechanical impurities, enters the fuel injector and adheres to the sealing cone surface of the needle valve body, causing pinning, cushioning, and contact Not tight (2) Due to the ablation of high-pressure and high-temperature gas in the combustion chamber, coupled with the frequent erosion of mechanical impurities in the fuel, pits and pits appear on the sealing ring between the needle valve and the needle valve body, causing the needle valve and the valve The sealing performance between the bodies deteriorates, and the phenomenon is that the oil return volume at the oil return hole of the injector increases. In this way, the high-pressure and high-temperature gas in the combustion chamber will enter the annular oil chamber of the injector during operation. Under the action of high temperature, the injector needle valve and the valve body are heated and expand and bite each other to death. (3) There are too many mechanical impurities in diesel oil, which will also cause impurities to enter between the needle valve and the guide surface of the valve body and bite to death. Because the needle valve of the injector is stuck to the valve body, the atomization performance of the diesel oil is deteriorated, the fuel injection time is too short and extends slightly backward, resulting in a too short ignition rate and combustion period, which makes the diesel engine work rough, so the diesel engine emits " Teng, Teng sound and obvious cylinder knocking sound. (4) Because the needle valve of the injector is not tightly sealed with the valve body or is stuck in the open position, the high-temperature gas in the combustion chamber enters the annular oil chamber of the injector, It will cause the injector to be hot. If the diesel engine is turned in this state, the compressed air generated in the cylinder will enter the annular oil chamber and oil passage through the opened nozzle hole, and be discharged from the high-pressure oil pipe, thus presenting a high-pressure oil pipe discharge. gas phenomenon.
