The phenomenon after the fuel injector needle valve burns out is that when the engine is working, there is no change in the engine working condition when tightening or loosening the pressure regulating screw on the fuel injector. In addition, due to the different locations where the injector needle is burned, the phenomena displayed when the engine is running are also different.

When the needle valve is burned open and the engine is running, there will be an irregular rhythmic metal knocking sound in the cylinder. At the same time, the exhaust pipe will also make a "pop, pop" sound, and the exhaust will be gray-white. The temperature of the high-pressure oil pipe of the injector is also higher than that of other cylinders. At this time, if the knocking sound disappears during the oil cutoff inspection, when the high-pressure oil pipe is loosened, fuel will be sprayed from the loosened place.

When the needle valve is burned in the closed state, the needle valve does not work when the engine is running, so the temperature of the high-pressure oil pipe of this cylinder is lower than that of other cylinders. When the cylinder is cut off for oil inspection, there is no change in the engine operation. From the high-pressure oil pipe Observe the loosened part, only fuel is injected, not air.

(1)Incorrect assembly method

① The anti-rust oil was not removed when installing the new oil nozzle. In order to prevent rust during storage and transportation, the fuel injection nozzle is generally coated with a layer of anti-rust oil. When replacing the fuel injector, if this oil is not cleaned away, the anti-rust oil will stick to the needle valve at high temperatures, causing the fuel injector needle valve to burn.

② Diesel leaks from the fuel injector. When the end face of the fuel injector is wet due to leaking diesel, it may cause surface combustion, and the heat of combustion is directly transferred to the fuel injector, causing the needle valve to burn.

③ When installing fuel injection, asbestos rope and other insulating materials are used instead of copper gaskets, which affects the heat dissipation of the fuel injection nozzle. The guide part of the fuel injection nozzle needle valve will overheat, causing the needle valve to become inflexible or even stuck.

④ When installing the fuel injector, the tightening torque of the screw sleeve is too large, which blocks the movement of the needle valve.

⑤The matching gap between the fuel injector and the fuel injector seat hole is too small. In this way, when the engine temperature is high, the original tiny gap of the needle valve assembly is destroyed, causing the injector needle valve to burn.

(2) There is dirt in the fuel oil line

Diesel oil contains too many impurity particles that are too large, which is currently the main reason for burning the injector needle valve. The fuel filter used by the engine can generally only filter out impurities larger than 0.05 mm. Obviously, the filtration 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, causing part of the fuel to directly enter the fuel injection pump, and the dirt in it may enter the fuel injector and clog it.

(3) The engine temperature is too high and the needle valve is burned out.

① The engine often runs at low speed for a long time, which causes the fuel injection pressure of the injector to decrease, and oil seeps around the injector to form carbon deposits, causing the temperature to rise and burn the needle valve.

② The oil rushes into the combustion chamber and causes a large amount of carbon deposits in the fuel injector after combustion, making it difficult for the heat to dissipate from the fuel injector and causing the needle valve to burn.