The injector is installed on the cylinder head, and the nozzle goes deep into the combustion chamber of the diesel engine, and works for a long time under the environment of high temperature, high pressure and gas corrosion. The internal moving parts are impacted by the high-speed flow of fuel and repeatedly washed by the small mechanical impurities in the fuel, which is very easy.
The cause of diesel injector failure
Poor atomization of fuel injector I
When the injection pressure is too low, there is carbon deposit in the nozzle wear, and the end face of the spring is worn or the spring force drops, it will cause the injector to open in advance, delay to close, and form the phenomenon of poor atomization.
If it is a single cylinder diesel engine, it will not work; if it is a multi cylinder diesel engine, the power will be reduced, the exhaust will emit black smoke, and the running sound of the machine will not be normal. In addition, because the diesel droplets with too large particle size can not be fully burned, they will flow into the oil pan along the cylinder wall, which will increase the oil level, reduce the viscosity and worsen the lubrication, and may also cause the accident of tile burning and cylinder pulling.
Solution: the fuel injector shall be disassembled for cleaning, maintenance and re commissioning.
The return pipe of the second injector is damaged
When the wear of the needle valve couple is serious or the fit between the needle valve body and the injector shell is not tight enough, the return oil volume of the injector increases obviously, some of which can reach 0.1-0.3 kg / h. If the oil return pipe is damaged or leaked, the oil return will be lost in vain, causing waste.
Therefore, the oil return pipe must be intact and sealed so that the oil can flow into the oil tank smoothly. If the return pipe is connected to the diesel filter, a check valve shall be set at its terminal to prevent the diesel in the filter from flowing back into the injector.
Needle valve orifice expansion
As the high-pressure oil flow continues to spray and wash, the injection hole of the needle valve will gradually grind larger, resulting in the decrease of the injection pressure, the shortening of the injection distance, the poor atomization of diesel oil, and the increase of carbon deposition in the cylinder.
Solution: the hole diameter of the single hole needle injector is generally greater than 1mm. A steel ball with a diameter of 4-5mm can be placed at the end of the hole, and it can be tapped gently with a hammer to make the local plastic deformation of the injection hole and reduce the hole diameter. Due to the large number of holes and small hole diameter, the porous direct injection injector can only be tapped gently on the hole end with the punching sample made of high-speed steel. If it is still unqualified after debugging, the needle valve coupling should be replaced.
Needle valve bites
The water or acid substance in the diesel oil will rust the needle valve and get stuck. After the sealing cone of the needle valve is damaged, the combustible gas in the cylinder will also rush into the mating surface to form carbon deposits, which will cause the needle valve to bite, and the injector will lose the injection effect, causing the cylinder to stop working.
Solution: heat the needle valve coupling in the waste oil until it boils and smokes, then take it out, clamp the tail of the needle valve with a pair of pliers padded with soft cloth and slowly move it out, dip it with clean oil, let the needle valve move and grind repeatedly in the valve body, until the valve can slowly exit from the valve body when the needle valve coupling is inverted. If the injector is not qualified in the test, the needle valve coupling shall be replaced.
Wear on the end face of five pin valve body
The end face of the needle valve body is impacted by the frequent reciprocating motion of the needle valve, which will gradually form a pit over a long period of time, thus increasing the lift of the needle valve and affecting the normal operation of the injector.
Solution: the needle valve body can be clamped on the grinder to grind the end face, and then the fine grinding paste can be used to grind the glass plate.
Six injector and cylinder head joint hole gas leakage oil channeling
When the fuel injector is installed in the cylinder head, the carbon deposit in the installation hole shall be carefully removed, and the copper gasket must be flat and shall not be replaced by asbestos plate or other materials, so as to prevent poor heat dissipation or failure to play a sealing role.
If the copper washer is made by ourselves, it must be processed with red copper according to the specified thickness to ensure that the distance between the injector and the cylinder head plane meets the technical requirements. In addition, the concave shape of the pressure plate of the fuel injector shall be installed downward, and unilateral bias shall not be allowed during tightening, and the pressure shall be tightened evenly according to the specified torque, otherwise the head of the fuel injector will leak gas and oil due to deformation and deflection.
Wear of seven needle valve and guide surface of needle valve hole
The frequent reciprocating movement of the needle valve in the needle valve hole, together with the invasion of impurities and dirt in the diesel oil, will gradually wear the needle valve hole guide surface, resulting in the increase of the gap or the occurrence of scratch marks, resulting in the increase of the internal leakage of the injector, the decrease of the pressure, the decrease of the injection quantity and the delay of the injection time, resulting in the difficulty of starting the diesel engine.
Solution: when the injection time is delayed too much, the locomotive can not even run, at this time, the needle valve coupling should be replaced.
Eight injector drips
When the injector works, the sealing conical surface of the needle valve body will be impacted frequently by the needle valve. In addition, the high-pressure oil flow will be continuously ejected from this place, and the conical surface will gradually appear nicks or spots, thus losing the seal, causing the injector to drip oil.
When the temperature of the diesel engine is low, the exhaust pipe emits white smoke, and when the temperature of the engine rises, it becomes black smoke, and the exhaust pipe will emit irregular shooting sound. At this time, if the oil supply to the cylinder is stopped, the smoke exhaust and shelling sound will disappear.
Solution: disassemble the fuel injector, dip a little chrome oxide fine grinding paste on the head of the needle valve (pay attention not to stick in the needle valve hole) to grind the conical surface, then wash it with diesel oil, and install it into the fuel injector for test. If it is still unqualified, the needle valve coupling shall be replaced.