1. Main reasons
The fuel injector spring is broken. The guide part and sealing cone of the fuel injector are severely worn. The nozzle needle valve body is in sealing contact with the injector housing, and the two surfaces are corroded or scratched. The shoulder foot part of the fuel injector coupling fastening nut is burned or the tightening torque of the fastening nut is not correct
The fuel injector is not thoroughly cleaned and the assembly is not clean. The fuel injector component bit deadly. The fuel injection pressure is too low. The steel ball inside the top rod of the fuel injector is lost or worn, causing the fuel injection pressure to remain low even when the pressure regulating screw is fully tightened. The pressure reducing ring of the fuel injection pump outlet valve is worn, causing incomplete fuel injection and oil droplets. The fuel injection pump has low oil pressure.
2. Check and diagnose
The main inspection for poor atomization of fuel injectors is as follows:
(1) Diesel fuel is injected in a linear pattern and cannot be atomized, or although it can be atomized, there are still visible oil droplets in the atomized oil beam. When the oil beam is injected, there is no pressure or insufficient pressure.
(2) The oil jet is off center. Usually, by carefully observing Ding with the eyes, one can detect whether the ejected oil beam is skewed.
(3) The fuel injection cone angle does not comply with regulations. The testing method is to vertically lower the fuel injector and place a piece of toilet paper below it at a distance of 100 millimeters from the fuel injector, so that the injector sprays vertically at normal working pressure. Then, the diameter of the oil stain on the toilet paper should be measured to be 25-35 millimeters (reference value for S195 diesel engine).
(4) There is a lot of oil leakage and return, and the fuel injector parts drip or soak severely. The start and end of the fuel injection are not clear, crisp, and the sound is not clear. The diagnosis of the sealing performance of the fuel injector head is to loosen the screw of the high-pressure oil pipe joint of the inspected cylinder, disconnect the cylinder for 10-20 seconds, and then quickly tighten the high-pressure oil pipe screw. At this point, if the diesel engine's sound returns to normal within 1 second, it indicates that the nozzle cone is well sealed; If it returns to normal after a few seconds, it indicates poor sealing of the needle valve cone surface; If the cylinder does not work or works intermittently, and there is air leakage from the oil pipe joint when the cylinder is disconnected (i.e. air guiding phenomenon), and the temperature of the fuel injector is extremely high, it indicates that the fuel injector of the cylinder is stuck.
3. Troubleshooting
(1) If it is found that the fuel injector is not tightly sealed, the sealing cone surface of the fuel injector can be ground with toothpaste. Be careful not to stick the grinding paste between the needle valve and the valve body, which may cause wear on the cylindrical mating surface. If the requirements cannot be met, it should be replaced.
(2) Check and adjust the fuel injection pressure. When the fuel injector is working normally, there is a uniform and continuous "clacking" sound, while when the fuel injection pressure is too low, there is a uniform and continuous "hissing" sound accompanied by black smoke. At this point, you can try adjusting the fuel injector injection pressure. If the pressure adjustment screw is tightened to the bottom and the injection pressure is still low, you should check whether the steel ball is worn or lost (1/8 "steel ball) and whether the top rod is broken. Excessive or insufficient fuel injection pressure will directly affect the performance of diesel engines.
① The method of adjusting fuel injection pressure on a diesel engine is to unscrew the return pipe connecting bolt on the fuel injector and remove the return pipe. Release the high-pressure oil pipe and fuel injector pressure plate, and remove the fuel injector. Turn the fuel supply pipe to an angle, install the fuel injector on the end of the high-pressure fuel pipe, and fix it
In a position that is easy to observe the fuel injection situation and easy to adjust. Pull the hand oil pump with the oil pump wrench, and observe the spray condition of the nozzle. Normally, there should be a "rattle" sound, and there should be no dripping, grainy or forked oil spray. Otherwise, it needs to be adjusted. When adjusting, first loosen the nut of the adjustment screw of the oil nozzle, tighten the adjustment screw while pumping oil until all the sprayed oil is atomized and makes a "creaking" sound. The above adjustments are ineffective. The fuel injector components can be cleaned or replaced with new components. The injection pressure of 165 series, 170 series, and 175 series small diesel engines is adjusted according to this method. Three way pressure gauge inspection method: Install a 60 megapascal three-way pressure gauge on the oil pump joint with good sealing of the plunger pair. At this time, the 60 megapascal pressure gauge and the oil pump form a simple fuel injector tester. Remove the fuel injector to be tested from the cylinder head, install it onto the side connector of the three-way pressure gauge through the high-pressure oil pipe, and pull the throttle to the maximum fuel supply position. When adjusting the fuel injection pressure, shake the crankshaft with a fuel injection frequency of 20-30 times per minute to make the fuel injector spray outwards, while observing the reading value of the pressure gauge pointer. Turn the pressure adjustment screw of the fuel injector, turn it to the left to decrease the pressure, and turn it to the right to increase the pressure. The reading of the pressure gauge pointer before it swings back is the injection pressure value on the fuel injector.
(3) If the oil mist cone angle is too large when the injector sprays oil, it may be caused by the nozzle hole of the needle valve body being enlarged due to high-pressure diesel flushing, and the needle valve needle having a too large reverse cone angle. When such faults occur, new parts should be replaced and old fuel injectors should be scrapped. The phenomenon of high-pressure diesel flushing causing the nozzle hole of the needle valve body to become larger is also rare, and the common fault at the joint between the needle and the nozzle hole is severe carbon deposition. After removing the carbon deposition, it can be ground.
(4) If all parts of the injector are normal and the oil pressure adjustment screw is slightly tightened, the injector will not spray oil, indicating that the plunger of the fuel injection pump is worn and the pump oil is weak. The fuel injection pump should be checked.
(5) If there is a dripping phenomenon when replacing the new fuel injector parts, the wear of the pressure reducing ring ring of the fuel injection pump outlet valve should be checked. If the oil outlet valve is slightly worn, then the manufacturing quality of the fuel injector is too poor.