Thoughts and methods for troubleshooting common faults of engine common rail injector

Thoughts and methods for troubleshooting common faults of engine common rail injector:

Common rail injector is precision matching parts of diesel engine system, the stand or fall of injector working condition directly affects the performance, fuel economy and reliability of the diesel engine, the fuel injector, it is not hard to see to the working principle of the fuel injector work need to have a stroke of injection pressure, injection and the suitable spray cone Angle, moreover injector when need to stop injection can quickly cut off fuel supply, not drip occur.

In the working process of fuel injector, there will be various kinds of faults and phenomena, so what are the thoughts and methods to eliminate the common faults of fuel injector? Let's take a look:

1. The nozzle is blocked

Because the fuel mixed with solid impurity particles, or because of poor combustion to produce carbon deposition, working time a little longer will accumulate in the injector around the nozzle, so that the nozzle into a semi-blocking state. Once the orifice is blocked, the oil pressure in the fuel pump rises with a tapping sound.

Prevention method: on the one hand, fuel entering the injector should be strictly filtered; On the other hand, by improving combustion, it prevents the orifice from being blocked by too much carbon accumulation.

2. Oil dripping from the nozzle

When injector work, needle valve body sealing cone will be the needle valve frequent strong impact, coupled with high pressure fuel constantly from the injection, cone will gradually appear wear or spots, resulting in fuel injector drops. When the temperature of the diesel engine is low, the exhaust pipe will emit white smoke. The exhaust pipe will emit the irregular sound of the cannon. At this time, if the oil supply to the cylinder is stopped, the smoke exhaust and the cannon sound will disappear.

Exclusion method: remove the nozzle, check the movement of the needle valve is flexible, seat surface sealing is good, and then carefully clean and develop or replace the new nozzle couple.

3. Nozzle corrosion and end carbon deposition

The nozzle corrosion is caused by the cold corrosion caused by the sulfide in the exhaust, and the corroded nozzle is caused by the chemical corrosion due to the too cold metal surface. Any nozzles found to be corroded should be replaced.

Carbon accumulation at the end of the nozzle is easy to form when the diesel engine is running at idle speed or under low load. As the load on the diesel increases, the carbon trapped in the nozzles burns off as the fuel is ejected. End carbon deposition has a certain impact on the atomization of fuel and the uniformity of fuel distribution in combustion, resulting in incomplete combustion, power reduction of diesel engine, and the occurrence of afterburning and various mechanical faults.

Removal method: remove the nozzle and remove the carbon deposition on the nozzle by mechanical or weak corrosion method. Carbon removal inside the orifice is important, but the sealing surface must be protected from damage. In order to prevent the steel wire used for clearance from breaking in the hole, the steel wire must be installed in the chuck, and the length of the steel wire exposing the nozzle shall not exceed 2 mm.

4. The needle valve is stuck

The moisture or acid in the diesel oil will make the needle valve rust and get stuck. After the seal cone of the needle valve is damaged, the flammable gas in the cylinder will also enter into the mating surface to form carbon deposition, making the needle valve bite to death. Then the fuel injector will lose the function of oil injection and cause the cylinder to stop working.

Removal method: remove the fuel injector, take out the fuel injector couple, and pull out the needle valve with a tool. If it is not easy to pull out, first put the fuel injector couple into the diesel oil for about 20 minutes and then take it out. When the needle valve on the tail gasket copper, with pliers clamp tail side rotation side to pull out. After pulling out, put it into the cleaning solution for cleaning, and then reload. If it is dirt invasion, it will be flexible after cleaning, if it is due to the geometric shape of the workpiece affected by the flexible, to add a small amount of grinding paste, gently grinding, grinding after cleaning.

5. Poor atomization of oil injector

When the injection pressure is too low, jet hole wear with carbon deposition, spring wear or elastic force drop, will cause the injector to open ahead of time, delay closing, and the formation of spray oil atomization phenomenon. The power of the diesel engine decreased, the exhaust emitted black smoke, and the noise of the machine was abnormal. In addition, because the particle size is too large diesel fog droplets can not fully combustion, it will flow down the cylinder wall into the oil pan, making the oil surface increased, viscosity decline, lubrication deterioration, may also cause burning vara cylinder accident. At this time, the injector should be disassembled for cleaning, maintenance and re-commissioning.

Spring snap

In addition to the permanent deformation of the injector's pressure-regulating spring due to the steel drop, the fracture also happens frequently, which has become one of the weak links of the injector. Mainly because of the high temperature, high load, high frequency of working conditions, spring steel poor fatigue strength.

Solution: to improve the fatigue strength, select high quality heat resistant and fatigue resistant materials, surface treatment and shot peening to enhance the fatigue strength. In order to make the pressure regulating spring work safely and reliably. Reduce the dynamic load of the spring, the injector can be designed into the spring can be immersed in the diesel fuel injector body, so that when the injector works, the working ring of the spring can produce hydraulic "buffer" and some lubrication, in order to prevent the formation of pitting surface on its contact surface and lead to the fracture of the spring.

7. Needle valve body end wear

The end face of the needle valve body is impacted by the frequent reciprocating movement of the needle valve, which will gradually form pits over a long period of time, thus increasing the lift of the needle valve and affecting the normal operation of the fuel injector. The needle valve body can be clamped onto the grinding machine for grinding this end face, and then grinding on the glass plate with fine grinding paste.

8. Needle valve and needle valve hole guide surface wear

The needle valve frequently reciprocates in the needle valve hole, together with the invasion of the impurity pollution in the diesel oil, will make the needle valve hole guide surface gradually wear out, thus the gap increases or appears the scratch mark, causes the fuel injector internal leakage to increase, the pressure reduces, the fuel injection quantity reduces, the fuel injection time lag, causes the diesel engine to start the difficulty. When the injection time delay is too much, the diesel engine can not even run, the needle valve couple should be replaced.

9. Fuel injector and cylinder head combined hole leakage oil channeling

When the fuel injector is installed in the cylinder head, the carbon accumulation in the mounting hole should be carefully cleared. The copper washer must be smooth and shall not be replaced by asbestos plate or other materials to prevent poor heat dissipation or lack of sealing effect. If the copper washer is made by yourself, it must be processed with copper according to the specified thickness to ensure that the distance of the injector extending out of the cylinder head plane meets the technical requirements. In addition, when the pressure plate of the injector is firmly installed, it shall not be one-sided bias by all means, and it shall be tightened evenly according to the specified torque, otherwise, the head of the injector will produce leakage and oil leakage due to deformation and deviation.

Damaged fuel injector return pipe

When the needle valve couple wear seriously or needle valve body and injector shell is not tight enough, the fuel injector return is significantly increased, some up to 0.1 -- 0.3 kg/h. If the oil return pipe is broken or leaky, the oil return will be lost, resulting in waste. Therefore, the return line must be intact and installed airtight so that the return oil can flow smoothly into the tank. If the oil return pipe is connected to the diesel filter, the terminal shall be equipped with a one-way valve to prevent the diesel oil in the filter from flowing into the injector.