Fuel Injector Nozzle DLLA324N413

Disassembly and Inspection of Injector Head and Grinding Repair Skills of Needle Valve Coupling (part 3)

1.3 Inspection

After cleaning, check all parts of the fuel injector, especially the needle valve coupling, to determine whether to replace or repair. The cylindrical guide surface of the needle valve is black, and at the same time, the needle valve is inserted into the needle valve body and feels loose, which proves that the clearance of the guide surface is large. When in use, there must be a lot of oil return, and the oil pressure cannot be adjusted high. Trying to increase the oil pressure may cause the pressure regulating spring to fail, and the oil will not be sprayed out.

The valve line of the needle valve plays the role of controlling the fuel injection volume, maintaining a certain injection pressure and ensuring good atomization of the fuel injection. If there are signs of damage, it is not sealed during use, and the atomization of the fuel injection is poor or cannot be atomized. At the same time, there is a phenomenon of dripping on the surface of the nozzle hole of the needle valve body.

There are traces of unevenness and damage on the joint plane of the large end of the needle valve body, which proves that it is not used well. If the defect is on the outer ring, the fuel will leak out during use; if the defect is on the inner ring, the fuel will leak to the oil return hole.

The fit between the nozzle hole of the needle valve body and the small head of the needle valve should not be too loose or too tight. If it is too loose, the atomization quality will decrease, the atomization will be less and the oil particles will be thicker, and the sound will not be crisp. If it is too tight, the fuel injection will form a line, and the fuel injection will not make a sound. If the fuel injection lasts too long, afterburning will easily occur.