Common rail injector working principle and common six fault detection.

The injector is a key component of the diesel engine, and its work directly affects the power, economy, emissions and reliability of the diesel engine. According to the requirements of mixture formation and combustion, the injector should have a certain injection pressure, injection stroke, and appropriate injection cone angle. In addition, the injector should be able to cut off the fuel supply quickly when it is necessary to stop the injection, without dripping. phenomenon.

Structure and working principle of common rail injector nozzles

OFF (no injection) => open (start injection) => full open (injection) => closed (injection reduction) => fully closed (stop injection)

● Initial state

When the injector solenoid valve is not triggered, the injector is closed, the drain hole is also closed, and the small spring presses the armature ball valve against the orifice to form a common rail high pressure in the valve control chamber, China-Lutong Engineer Mr.Wang said. Similarly, a common rail high pressure is also formed in the injector, and the common rail pressure balances the pressure of the control plunger section and the pressure of the nozzle spring with the opening force of the high pressure fuel on the tapered surface of the needle valve, so that the needle valve remains closed. status.

● Fuel injection start status

When the solenoid valve is triggered, the armature opens the drain hole, the fuel flows from the valve control chamber to the upper cavity, and returns from the cavity to the oil tank through the oil return pipe, so that the control chamber pressure is lowered; the control chamber pressure is reduced, and the pressure is reduced. The force acting on the control plunger, at which point the nozzle needle is opened and the injector begins to inject oil.

● End of injection

Once the solenoid valve is powered off, the force of the small spring will not be triggered, and the solenoid valve will be pressed down. The ball valve will close the drain hole. After the drain hole is closed, the fuel will enter the control chamber from the oil inlet hole to establish the oil pressure. This high pressure is controlled. On the cross section of the plunger, the rail pressure plus the spring force is greater than the pressure on the conical surface of the needle valve, causing the diesel nozzle needle to close.

Common rail system components are sensitive to water in the fuel system, especially injectors with precision valve assemblies that are inherently diesel lubricated. Once the system enters the water, it may cause problems such as rust or poor lubrication of the parts.

Common injector fault detection

01. Injector bad atomization

Fault phenomenon: The diesel engine power is reduced, the exhaust gas is black smoke, and the machine running sound is not normal.

Fault analysis: When the injection pressure is too low, the nozzle wears carbon, the spring end face wears or the elastic force decreases, the injector will be opened in advance, delayed to close, and the injection atomization phenomenon will be formed. In addition, since the diesel droplets having an excessively large particle diameter cannot be sufficiently burned, they flow into the oil pan along the cylinder wall, so that the oil oil surface is increased, the viscosity is lowered, the lubrication is deteriorated, and an accident of the burnt cylinder may be caused.

02. The injector is stuck

Symptom: Engine power drops, jitter, and can't even start.

Fault analysis: The moisture or acid in the diesel oil will cause the needle valve to rust and get stuck. After the sealing cone of the needle valve is damaged, the combustible gas in the cylinder will also enter the mating surface to form carbon deposit, so that the needle valve will be killed and sprayed. The oil loses the fuel injection, causing the cylinder to stop working.

03. Needle valve and needle valve hole guide surface wear

Symptom: The power is reduced, the engine is difficult to start, and it cannot even start.

Fault analysis: the needle valve reciprocates frequently in the needle valve hole, and the intrusion of impurities in the diesel oil will cause the guide surface of the needle valve hole to wear gradually, so the gap is increased or the scratch is scarred, resulting in leakage inside the injector. The increase, the pressure is reduced, the fuel injection amount is reduced, and the injection time is delayed, which makes the diesel engine difficult to start. When the injection time delay is too much, the diesel engine can't even run. At this time, the needle valve coupler should be replaced.

04. Fuel injector drip

Fault phenomenon: When the diesel engine temperature is low, the starting is difficult, the exhaust pipe emits white smoke, and the diesel engine temperature becomes black smoke. And the fuel consumption is high.

Fault analysis: When the injector is working, the sealing cone of the needle valve body will be frequently and strongly impacted by the needle valve. In addition, the high-pressure fuel is continuously ejected from the place, and the cone surface will gradually wear or spot, thus causing the fuel injection. Drip oil. When the temperature of the diesel engine is low, the exhaust pipe emits white smoke, and when the temperature of the diesel engine rises, it becomes black smoke. Check that the movement of the needle valve is flexible, the cone surface should be free of wear and the seal is otherwise required to replace the new nozzle nozzle.

05. The oil return is too high

Fault phenomenon: the injection pressure is reduced, the injection time is delayed, the engine power is reduced, and even the diesel engine is turned off.

Fault analysis: When the needle valve part is seriously worn or the needle valve body and the injector shell are not tightly matched, the oil return of the injector is obviously increased, and the valve plate is also required to be noticed. This causes the injector to return too much oil and affects engine performance.

06. Solenoid valve electromagnetic coil melting

Symptom: The injector does not work properly;

Fault analysis: the power supply voltage is too large or the power-on time is too long, causing the solenoid valve coil to melt;

Solution: It is forbidden to manually power up the injector;

Contact: Mr.Rodge

Skype: rodge_chinalutong

Whatsapp: 008613859818106

E-mail: rodge@china-lutong.com