Analysis of common faults of fuel injector

Analysis of common faults of fuel injector

1.1 oil dripping of fuel injection nozzle

Fault signs: fuel injection continues and the injection hole is blocked, which makes the fuel unable to be atomized, uneven fuel injection quantity, poor starting performance, working knocking, exhaust smoke and carbon deposition increase, resulting in the decrease of engine power, increase of fuel consumption and increase of wear.

Fault analysis: (1) the sealing conical surface of the needle valve and the needle valve body is seriously worn, with groove marks, which widens the contact surface of the conical sealing ring, deforms the conical surface, and increases the roughness, resulting in oil dripping from the nozzle, carbon deposition near the nozzle, and even plugging the nozzle. (2) The higher the residual pressure of the high-pressure oil pipe (that is, the pressure when the high-pressure oil pipe does not inject oil between two times of the injection nozzle) is, the more serious the oil dripping of the injection nozzle is. The main reason that affects the residual pressure is the oil outlet valve coupling. The oil dripping fault of the fuel injection nozzle is not all on the fuel injection nozzle, but closely related to the tightness of the oil outlet valve coupling. Abnormal wear of the oil outlet valve will cause oil dripping of the fuel injection nozzle. (3) The poor sliding and work blocking of the needle valve and the guide surface of the needle valve body, or the serious abrasion of the needle valve and the guide surface of the needle valve body, the loose contact between the needle valve body and the injector body, or the sealing cone of the needle valve and the needle valve body is padded and closed by mechanical impurities, will also cause the oil dripping of the nozzle.

1.2 the seal between the needle valve and the valve body of the injector is not tight and is blocked

Trouble signs: the low-pressure oil circuit is unblocked, the speed control handle is placed at the oil supply position, and the diesel engine is cranked. The injection sound of the fuel injector cannot be heard by individual cylinders, and the exhaust pipe emits white smoke and is not easy to catch fire. When the diesel engine is on fire, the exhaust pipe still emits smoke, the idle speed is not stable, accompanied by the "Teng, Teng" gasping sound, and the high-speed and the gas pedal is accompanied by the obvious knocking sound. When the temperature of the diesel engine increases, the exhaust pipe emits black smoke, the fuel injector burns, and the fire "lacks legs". Disassemble the high-pressure oil pipe of the leg missing cylinder. The exhaust pipe of the diesel engine will not smoke, and the knocking sound will disappear. But there is an exhaust phenomenon and foam discharge at the high pressure oil pipe joint of injector.

Fault analysis: (1) during the working process of diesel engine, the high-pressure diesel oil pumped from the injection pump carries some mechanical impurities into the fuel injector and adheres to the sealing cone of the needle valve body, causing card sticking and pad up, resulting in loose contact. (2) Due to the ablation of high pressure and high temperature gas in the combustion chamber, coupled with the frequent flushing of mechanical impurities in the fuel oil, there are pockmarks and pits on the sealing ring belt between the needle valve and the needle valve body, which leads to the deterioration of the sealing performance between the needle valve and the valve body. The phenomenon is that the oil return volume at the oil return hole of the injector increases. In this way, the high pressure and high temperature gas in the combustion chamber will enter the annular oil chamber of the injector. Under the action of high temperature, the needle valve and the valve body of the injector are heated and expanded, and they bite each other. (3) Too many mechanical impurities in diesel oil will also cause impurities to enter between the needle valve and the valve body guide surface and bite. Because the needle valve and the valve body of the injector are locked, the atomization performance of the diesel oil is poor, the injection time is too short and slightly extended backward, resulting in the short burning period of the fire speed, which makes the diesel engine work rough, so the diesel engine makes "Teng, Teng" sound and obvious knocking sound. (4) Because the needle valve and the valve body of the injector are not sealed tightly or locked in the open position, the high temperature gas in the combustion chamber enters the annular oil chamber of the injector, causing the injector to burn. If the diesel engine is cranked in this state, the compressed air generated in the cylinder will enter the annular oil chamber and oil passage through the open injection hole, and be discharged from the high-pressure oil pipe, thus presenting the phenomenon of high-pressure oil pipe exhaust.