How to Repair Stuck Injection Needle Valve?

Injection needle valve is one of three couple precision elements of diesel engine fuel supply system. Its normal service life is more than 1000h. But due to improper use, it will often be worn and stuck after hundreds of hours or even dozens of hours.

The main reasons of stuck injection needle valve are:

①The diesel is not clean and the high pressure tube contains impurities, which accelerates the abrasion of diesel injector nozzle and make the closure of diesel injector nozzle lax. The high pressure gas in combustion chamber channels, burning out injection nozzle elements. In addition, the dirt on the injector pressure regulating spring, tappet and other parts will move to the inside of fuel injector through fuel injector tappet. Cotton rope, lead wire etc used to prevent oil leakage in the oil way may enter into the injector through high pressure oil tube, which can make injector element clogged. 

②Two high the machine temperature and poor cooling of injector causes clogged injector element. And when oil delivery time is too late, the scale in the cooling waterway is too much or blocked, the pump impeller end surface is worn or diesel engine is suffered long-term overload operation, the diesel engine will be overheating. 

③If the delivery valve is worn and the oil drips when the injector stops injecting, it will make the injector burn to coke and appear stuck fault. 

④Injection pressure is too low,  resulting in high pressure gas of the combustion chamber channeling. 

⑤Gaskets were missed or destroyed when fuel injection installed, causing leakage and the local temperature of fuel injector too high to stuck. 

⑥The reason of parts machining, for example the mounting hole of injector on cylinder head fits tightly with injector, the clearance between injector and mounting hole of injector on cylinder is too small, mounting hole of injector on cylinder head is too deep etc

 

2. The danger of stuck injection needle valve

Injector elements stuck has the following effects on the diesel engine:

①. The power is not enough for diesel engine. If the injector element is completely jammed, fuel will not be sprayed into the cylinder, which leads to the individual cylinder of diesel engine inoperation. Therefore, insufficient power happens.    

②Diesel engine discharges black smoke. If the injector’s element don’t stuck completely, but movement is not flexible , may cause the drip of injector, etc, which makes diesel engine discharge black smoke owing to poor combustion. 

③The oil level of oil sump rises. Serious seepage of diesel injector element will make the injection of fuel in the cylinder cannot be fully mixed with air. Part of the fuel enters into the oil pan through the wall of air cylinder, resulting in the oil level of machine oil rising. 

④If the diesel engine work in the state of drip of diesel injector element, which will have some faults similar to the top of piston’s ablation、scratch or bearing abnormal damage etc. 

⑤In some cases, diesel engine may appear deflagration or detonation. 

Therefore, when the above faults were found in the diesel engine, the injector elements should be checked timely and repaired, preventing its working with faults from causing more serious damage to diesel engine. 

 

3.The methods for stuck injection needle valve:

①Firstly, heat the stuck injector in the diesel or oil. Then, take out and cover it with cloth. Nip the needle valve with pliers or other tools and move slowly, until needle valve withdraws from needle valve body. 

②Inject a small amount of clean oil into the needle valve body. Make needle valve move in the needle valve body over and over again, until it can move freely. If the sealing surfae of needle valve has the traces of burns, grind it by using abrasive paste. 

③Dosage and milling time of grinding paste need to be focused during grinding. 

④Install injector element inside the injector after being cleaned. Pay attention to the tighten force of holding-down nut on injector element, and adjust the pressure of injection. Then, diesel engine can be used again.