(3)Expansion of nozzle needle valve hole
As the high-pressure oil flow continuously spray and scouring, nozzle needle valve holes will be expanded, leading to injection pressure drop, spray distance shortened, diesel atomization getting poor, cylinder carbon accumulation increases.
Solution: Single Hole shaft needle injector aperture is generally bigger than 1mm, place a steel ball(diameter of 4~5 mm) at the end of hole, knock with a hammer lightly, so that the hole become narrow. for porous direct injection injector, because of the number of holes, small aperture,  you’d better replace the needle valve into a new.
(4) Needle valve get stuck
the water or acidic substances in diesel will make the needle valve rust and get stuck, needle valve seal cone damaged, the cylinder combustible gas will also flow into to form carbon, so that the needle valve get stuck, the injector will lose the role of fuel injection, resulting in the cylinder stop work.
Solution: Put the needle valve in the waste oil to heat until boiling and smoke, then take out,  clamp the needle valve tail slowly moving by a hand clamp with a soft cloth, take it out and  coat some clean oil, put it in the valve body, moving and grinding, until the needle valve can come out of  valve body from the valve itself slowly when invert. If the injector test is not qualified, you should replace the needle valve.