Disassembly Sequence and Maintenance Method of Fuel Injector of Diesel Engine

The fuel injector is also an important part of the fuel supply system of the diesel engine. Its function is to spray the high-pressure diesel oil from the fuel injection pump into the combustion chamber in the form of mist, and form a good combustible mixture with the compressed air in the combustion chamber. The fuel injector not only determines the spray quality of diesel, the cooperation between the oil beam and the combustion chamber, but also affects the fuel injection advance angle, fuel injection duration and fuel injection regularity, which have a direct impact on the performance of the engine. Therefore, the basic requirements for the work of the injector are: a certain injection pressure and range, as well as an appropriate spray cone angle, and match with the shape of the combustion chamber. In addition, the fuel injection can be stopped quickly at the end of the fuel injection without oil dripping.

one: fuel injector maintenance

After cleaning the injector parts, if any of the following abnormal conditions are found, they should be repaired or replaced. When the end face of the injector body combined with the needle valve body has minor damage, pull out the two positioning pins and grind the plate Grind on. Be careful not to touch the rough end surface when pulling out the positioning pin.
② When the surface of the pressure regulating spring of the fuel injector is scratched, pitted or permanently deformed, it should be replaced.
③ The carbon deposits in the inner shoulder blade and hole wall of the injector tight cap should be completely removed.
④ The diameter part of the fuel injection nozzle assembly is worn, and it should be replaced if there is serious oil leakage.
⑤ When the nozzle holes have defects such as wear and enlargement, those that affect the spray quality should be replaced.
⑥ If the sealing seat surface of the needle valve and needle valve body is not too worn, it can be repaired by mutual grinding with alumina abrasive paste. When grinding each other, do not use too much force, and the sealing surface can reach a uniform and not too wide sealing band.
⑦ Due to the backflow of gas in the diesel engine cylinder or the intrusion of fine impurities into the fuel injector, the needle valve becomes black or stuck. After cleaning and mutual research, it can be reused or replaced according to the severity of the situation.

two: Matters needing attention in injector assembly

① During the entire fuel injector assembly process, the parts must be kept clean, especially the seals of the fuel injector assembly itself and the end face of the injector body. Even small debris and dust can cause sliding blockage and The sealing of the contact surface is poor. The scapular surface where the tight cap of the fuel injector contacts the fuel injector should be smooth and flat, and no carbon deposits or burrs are allowed, otherwise it will affect the coaxiality and verticality of the installation of the fuel injector assembly, thereby causing the sliding of the fuel injector bad.
② When assembling, first screw in the oil inlet pipe joint that is pre-equipped with an oil filter core, and press the copper gasket tightly to achieve a tight seal without oil leakage. Then put the pressure regulating spring and ejector rod into the injector body, screw in the pressure regulating screw until it just touches the pressure regulating spring, and then screw on the pressure regulating nut.
③ Clamp the fuel injector upside down on the bench vise, install the fuel injector assembly, and tighten the cap. The tightening torque is 59-78 N.m (6-8kgf.m). Too much torque will cause deformation of the needle valve body, affecting the sliding performance of the needle valve, and too small torque will cause oil leakage.
④ The assembled fuel injector assembly should be tested on the test bench for sealing and spraying, and the opening pressure of the fuel injection should be adjusted.