Diesel injector common failures and solutions

        The so-called injector it is a very high precision precision devices (the most sophisticated is the most sophisticated needle valve and needle valve body), mainly to receive the injection pulse signal sent by the ECU, accurate control of fuel injection amount.General injectors can be divided into four types: shaft needle type electromagnetic injector, ball valve type electromagnetic injector, disc valve type electromagnetic injector, the lower oil injector.

　　

        The fault of injector is caused by fouling in diesel engine. The main reason is that the injector head in the combustion chamber is in the environment of high temperature and high pressure for a long time. Due to the influence of thermal expansion and cold contraction, the needle valve slowly expands and deformed or the fuel injection port is blocked by carbon accumulation. The amount of fuel injection decreases and the fuel injection cannot be normally injected gradually, thus affecting the normal operation of the diesel engine. General injector fault has the following points, the common fault of injector and troubleshooting methods are introduced as follows.

 

 

        When the injection pressure is too low, there is carbon accumulation in the jet hole wear, spring end wear or elastic force drop, will cause the injector to open ahead of time, delay closing, and form the phenomenon of poor spray atomization. If the single cylinder diesel engine can not work, multi-cylinder diesel engine power decline, exhaust smoke, the operation of the machine sound is not normal. In addition, because the particle size is too large diesel fog droplets can not fully combustion, then along the cylinder wall into the oil pan, make the oil oil surface increased, viscosity decline, lubrication deterioration, may also cause burning vara cylinder accident. Solution: the injector should be disassembled for cleaning, maintenance, re-commissioning.

 

　　

 

        When the needle valve couple wear seriously or needle valve body and injector shell with not tight enough, the fuel injector return significantly increased, some up to 0.1 ~ 0.3 kg/h. If the oil return pipe is broken or leaky, the oil return will be wasted. Therefore, the return line must be intact and installed airtight so that the return oil can flow smoothly into the tank. If the oil return pipe is connected to the diesel filter, the terminal shall be equipped with a one-way valve to prevent the diesel oil in the filter from pouring into the injector.

　　

 

        As the high-pressure oil flow is continuously sprayed and scour, the nozzle hole of the needle valve will be gradually grinded and enlarged, resulting in the decrease of injection pressure, the shortening of injection distance, poor diesel atomization, and the increase of carbon accumulation in the cylinder.

        Solution: the hole diameter of the single-hole axle-pin injector is generally greater than 1 mm. A steel ball with a diameter of 4 ~ 5 mm can be placed at the end of the hole and knocked gently with a hammer to make the local plastic deformation of the nozzle and reduce the hole diameter. Due to the large number of holes and small aperture, the perforated direct injection injector can only be tapped gently at the hole end with the high-speed steel blanking sample. If it still fails after debugging, the needle valve couple should be replaced.
　　

 

        The water or acid substance in the diesel oil will make the needle valve rust and get stuck. After the seal cone of the needle valve is damaged, the combustible gas in the cylinder will also enter into the mating surface and form carbon deposition, making the needle valve bite to death. Then the fuel injector will lose the function of oil injection and cause the cylinder to stop working.

        Solution: the needle valve can be couple in the used oil heated to boiling in the smoke, then remove and use pad with a soft cloth hand vice clamp needle tail slowly, it drew on clean oil, let the needle valve in the valve body activity grinding repeatedly, until the needle valve can couple the horse hour hand valve from the valve body to slowly withdraw from. If the injector loaded test is not qualified, the needle valve couple should be replaced.

 

 

       The end face of the needle valve body is impacted by the frequent reciprocating movement of the needle valve, which will gradually form pits over a long period of time, thus increasing the lift of the needle valve and affecting the normal operation of the fuel injector.

        Solution: the needle valve body can be clamped to the grinding machine for grinding this end face, and then use fine grinding paste on the glass plate for grinding.

　　

        When the fuel injector is installed in the cylinder head, the carbon accumulation in the installation hole should be carefully cleared. The copper washer must be flat and shall not be replaced by asbestos plate or other materials to prevent poor heat dissipation or lack of sealing effect. If the self-made copper washer, it must be processed with red copper according to the specified thickness to ensure that the distance of the injector extending out of the cylinder head plane meets the technical requirements. For example, this distance of 135 series diesel engine is 1.5-2mm, which will affect the cylinder compression ratio. In addition, the concave shape of the fuel injector pressing plate should be installed face down, and unilateral bias should be avoided in the tightening process. It should be tightened evenly according to the specified torque, otherwise the fuel injector head will produce leakage and oil channeling due to deformation and deviation.
　　

 

        The needle valve frequently reciprocates in the needle valve hole, together with the diesel oil impurities and dirt invasion, will make the needle valve hole guide surface gradually wear, so the gap increases or appears the scratch mark, resulting in increased leakage in the injector, pressure reduction, injection amount reduction, injection time lag, resulting in the diesel engine starting difficult.

        Solution: when the injection delay too much, the locomotive can not run, even a needle should be replaced at this time I thing.

　　

 

        When injector works, the sealing cone face of needle valve body can be subjected to the strong impact of needle valve frequently, plus the high-pressure oil flow is jetting out from this place continuously, the cone face can appear Nick or spot gradually, lose sealing thereby, cause injector drop oil. When the temperature of the diesel engine is low, the exhaust pipe will emit white smoke, which will turn into black smoke when the engine temperature rises. If the oil supply to the cylinder is stopped, the sound of smoke and cannon will disappear.

        Solution: with detachable fuel injector, the needle valve head touch a little chrome oxide thin paste (be careful not to touch the needle valve hole) was carried out on the cone grinding, then washed with diesel oil into fuel injector test. If still not qualified, the couple need to change the needle valve.