The needle valve of the fuel injector burns to death
The phenomenon that the needle valve of the fuel injector burns to death is that when the engine is working, when the pressure regulating screw on the fuel injector is tightened or loosened, the working condition of the engine does not change. In addition, due to the different positions where the needle valve of the fuel injector burns to death, the phenomenon shown when the engine is running is also different.
When the needle valve burns to death in the open state, when the engine is working, there will be a metal knocking sound without a certain rhythm in the cylinder. At the same time, the exhaust pipe will also make a “pop, pop” sound, and the exhaust is gray-white. The temperature of the injector’s high-pressure oil pipe is also higher than that of other cylinders. At this time, if the knocking sound disappears when the fuel is cut off, when the high-pressure fuel pipe is released, a jet of fuel will be sprayed from the release point.
When the needle valve burns to death in the closed state, the needle valve does not work when the engine is working, so the temperature of the high-pressure oil pipe of this cylinder is lower than that of other cylinders. When the cylinder is checked for oil cut, there is no change in the operation of the engine. Observe the loosening position, only spray oil, not jet.
The main reasons that cause the fuel injector needle valve to burn are:
(1) Incorrect assembly method
① The anti-rust oil was not removed when installing a new oil nipple. In order to prevent rusting during storage and transportation, the fuel injection nozzle is generally coated with a layer of anti-rust oil. When replacing the fuel injector, if the oil is not cleaned off, the anti-rust oil will stick the needle valve at high temperature, causing the fuel injector needle valve to burn.
②The fuel injector leaks diesel oil. When the end of the fuel injector is wet due to the leakage of diesel fuel, it may cause the surface to burn, and the heat of combustion is directly transferred to the fuel injector, causing the needle valve to burn.
③When installing the fuel injection, heat-insulating materials such as asbestos rope are used instead of copper washers, which affects the heat dissipation of the fuel injection nozzle. The needle valve guide part of the fuel injection nozzle will overheat and cause the needle valve to move inflexibly and even get stuck.
④The torque of the tightening screw sleeve of the injector is too large during installation, which will block the movement of the needle valve.
⑤The clearance between the injector and the injector seat hole is too small. In this way, when the engine temperature is high, the original very small gap of the needle valve assembly is damaged, causing the injector needle valve to burn to death.
(2) There is dirt in the fuel oil circuit
Diesel contains too many impurity particles, which is the main reason that the needle valve of the fuel injection nozzle burns. The fuel filter used in the engine generally can only filter out impurities larger than 0.05 mm. Obviously, the filtering ability is not too strong. If the fuel filter element is ruptured at this time, the upper and lower felt pads of the filter element are missing or damaged, so that part of the fuel enters the fuel injection pump directly, and the dirt may enter the fuel injection nozzle and block it.
(3) The engine temperature is too high to burn out the needle valve
① The engine frequently runs at low speed for a long time, causing the injection pressure of the injector to decrease, and the oil leaks around the injector to form carbon deposits, which causes the temperature to rise and burn the needle valve to death.
②The engine oil flees into the combustion chamber, causing a large amount of carbon deposits in the fuel injection nozzle after burning, making the heat of the fuel injection nozzle difficult to radiate and causing the needle valve to burn.