The fuel injector is a key part of the diesel engine, and its working quality directly affects the power, economy, emission and reliability of the diesel engine. According to the requirements of mixture formation and combustion, the fuel injector should have a certain injection pressure, injection stroke, and appropriate fuel injection cone angle. In addition, the fuel injector should be able to quickly cut off the fuel supply when the fuel injection needs to be stopped without oil dripping. Phenomenon.
The components of the common rail system are sensitive to the water in the fuel system, especially the parts with precision valve components such as the injector, which are lubricated by diesel oil. Once the system enters water, it may cause problems such as corrosion of parts or poor lubrication. The common injector faults mainly include:
● Poor atomization of fuel injector
Symptoms of failure: The power of the diesel engine drops, the exhaust emits black smoke, and the sound of the machine is abnormal.
Fault analysis: When the fuel injection pressure is too low, the nozzle hole wears and has carbon deposits, the end surface of the spring wears or the elastic force decreases, the fuel injector will open early and close late, and poor atomization of fuel injection will occur. In addition, because the diesel mist with too large particle size cannot be fully burned, it will flow into the oil pan along the cylinder wall, which will increase the oil level of the engine oil, decrease the viscosity, deteriorate the lubrication, and may cause an accident of burning the cylinder.
● The needle valve is stuck
Symptoms of failure: engine power drops, shakes, and even fails to start.
Fault Analysis: Moisture or acidic substances in the diesel will cause the needle valve to corrode and get stuck. After the needle valve sealing cone surface is damaged, the combustible gas in the cylinder will also rush into the mating surface to form carbon deposits, causing the needle valve to bite to death. The oiler will lose its fuel injection effect, causing the cylinder to stop working.
● The guide surface of the needle valve and the needle valve hole is worn
Symptoms: The power is reduced, the engine is difficult to start, or even unable to start.
Fault Analysis: The needle valve reciprocates frequently in the needle valve hole, coupled with the intrusion of impurities in diesel oil, the guide surface of the needle valve hole will gradually wear out, so the gap increases or scratches appear, resulting in internal leakage of the injector increase, the pressure decreases, the fuel injection volume decreases, and the fuel injection time lags, causing difficulty in starting the diesel engine. When the fuel injection time is delayed too much, the diesel engine cannot even run, and the needle valve coupling should be replaced at this time.
● Oil dripping from injector
Fault phenomenon: When the temperature of the diesel engine is low, it is difficult to start, and the exhaust pipe emits white smoke, and when the temperature of the diesel engine rises, it becomes black smoke. And high fuel consumption.
Fault Analysis: When the injector is working, the sealing cone surface of the needle valve body will be subjected to frequent strong impacts from the needle valve, coupled with the continuous injection of high-pressure fuel, the cone surface will gradually appear worn or spotted, resulting in fuel injection dripping oil. When the temperature of the diesel engine is low, the exhaust pipe emits white smoke, and when the temperature of the diesel engine rises, it turns into black smoke. Check whether the movement of the needle valve is flexible, the taper surface should be free of wear and tight, otherwise it is necessary to replace the nozzle assembly with a new one.
● Oil return volume is too high
Fault phenomenon: the fuel injection pressure is reduced, the fuel injection time is delayed, the engine power is reduced, and even the diesel engine is stalled.
Fault analysis: When the needle valve coupling is severely worn or the needle valve body and the injector housing are not tightly matched, the oil return volume of the injector will increase significantly. At the same time, it is also necessary to pay attention to the valve plate, which will also The oil return volume of the injector is too large, which affects the performance of the engine.
● initial state
When the solenoid valve of the fuel injector is not triggered, the fuel injector is closed, and the oil drain hole is also closed, and the small spring presses the ball valve of the armature to the throttle hole, forming a common rail high pressure in the valve control cavity. Similarly, the common rail high pressure is also formed in the fuel injector, and the common rail pressure maintains a balance between the pressure of the control plunger section and the pressure of the nozzle spring, and the opening force of the high-pressure fuel acting on the needle valve cone surface, so that the needle valve remains closed. state.
● Fuel injection start state
When the solenoid valve is triggered, the armature will open the drain hole, and the fuel will flow from the valve control chamber to the upper cavity, and return to the fuel tank from the cavity through the oil return pipe, reducing the pressure in the control chamber; When the force acting on the control plunger is released, the nozzle needle valve is opened and the injector starts to inject fuel.
● Fuel injection end state
Once the solenoid valve is powered off and is not triggered, the force of the small spring will press the solenoid valve down, and the ball valve will close the oil drain hole; after the oil drain hole is closed, the fuel enters the control room from the oil inlet hole to build up oil pressure, and this high pressure acts on the control chamber. On the plunger section, the rail pressure plus the spring force is greater than the pressure on the cone surface of the needle valve, so that the nozzle needle valve is closed.
● Conclusion:
In order to avoid abnormal damage to the injector, it is necessary to change the oil according to the season and maintain the diesel filter regularly. Avoid low-quality fuel and low-quality filters, and avoid long-term high-load operation of the engine. At the same time, it should be pointed out that the common rail system is a high-pressure system, please do not disassemble it without authorization to avoid injury, and the injector is a precision component, please choose a professional maintenance point for maintenance. Do not disassemble without authorization to avoid secondary damage to the injector.
