How Fuel Injectors Work

You known, fuel injector is one of the important parts of you car. So it is important for us to learn something about how it works. In this article, I will tell you some knowledge on this aspect.


Fuel Injector Diagram


The circuit diagram of the fuel injector is shown in the figure below. The engine control unit controls the opening of each fuel injector individually. The power supply of the fuel injector is the 12V battery voltage sent by the SC2210A fuse through the address code 38. The engine control unit controls the opening of the 1-cylinder, 2-cylinder, 3-cylinder, and 4-cylinder injectors through T80 / 79, T80 / 59, T80 / 73, and T80 / 65, respectively.


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J220-Motronic control unit; J519-vehicle power grid control unit; N30-1 cylinder fuel injector; N31-2 cylinder fuel injector; N32-3 cylinder fuel injector; N33-4 cylinder fuel injector; T2aq-2 core black Plug connection; T2ar-2 core black plug connection; T2as-2 core black plug connection; T2at-2 core black plug connection; T14a-14 core black plug connection, behind the left headlight in the engine compartment; T80-80 core black plug Connection; connection in E48-injector harness (fuel injector).



Fuel Injector Working Principle


When the fuel injector is not injecting oil, the return spring presses the needle valve tightly against the valve seat through the armature to prevent dripping. When the electromagnetic coil is energized, it generates electromagnetic attraction force, which attracts the armature and drives the needle valve away from the valve seat. At the same time, the return spring is compressed, and the fuel passes through the needle valve and is ejected from the annular gap or injection hole of the shaft needle and the nozzle.


When the electromagnetic coil is powered off, the electromagnetic suction force disappears, the return spring quickly closes the needle valve, and the fuel injector stops fuel injection.


When the structure of the fuel injector and the fuel injection pressure are fixed, the fuel injection quantity of the fuel injector depends on the opening time of the needle valve, that is, the energizing time of the electromagnetic coil. The spring force of the return spring will have an effect on the tightness of the needle valve and the crispness of the fuel injector.


Fuel Injector Function


First, increase oil pressure (constant pressure): increase the injection pressure to 10MPa-20MPa.


Second, control of fuel injection time (timing): fuel injection and stop fuel injection according to the specified time.


Third, control the fuel injection quantity (quantitative): According to the working condition of the diesel engine, change the fuel injection quantity to adjust the speed and power of the diesel engine. The fuel injector accepts the fuel injection pulse signal sent by the ECU to precisely control the fuel injection quantity. Injector is a precision device with very high processing accuracy, which requires a large dynamic flow range, strong anti-clogging and anti-pollution capabilities and good atomization performance.


Fuel Injector Problems Symptoms


Common fuel injector failures are as below:


A. Poor atomization of the injector


Trouble phenomenon: The power of the diesel engine is reduced, the exhaust smoke is black, and the sound of the machine is not normal.

Failure analysis: When the injection pressure is too low, the injection hole wears carbon deposits, the spring end face wears or the elastic force drops, it will cause the injector to open early, close late, and form a bad phenomenon of injection atomization. In addition, because the diesel droplets with an excessively large particle size cannot be fully burnt, they flow into the oil pan along the cylinder wall, increasing the oil level of the engine oil, reducing the viscosity, and deteriorating the lubrication. It may also cause the accident of burning the Vara cylinder.


B. Needle valve stuck

Fault phenomenon: The engine power drops, shakes, and even can’t start.

Failure analysis: Moisture or acidic substances in diesel will cause the needle valve to rust and be stuck. After the needle valve sealing cone is damaged, the combustible gas in the cylinder will also penetrate into the mating surface to form carbon deposits, which will cause the needle valve to bite The oiler loses its fuel injection effect, causing the cylinder to stop working.


C. The guide surface of the needle valve and the needle valve hole is worn

Trouble phenomenon: The power is reduced, the engine is difficult to start, or even unable to start.

Failure analysis: The needle valve frequently reciprocates in the needle valve hole, coupled with the intrusion of impurities in the diesel, the guide surface of the needle valve hole will gradually wear out, so the gap increases or the scratches appear, resulting in leakage in the injector The increase, the pressure decreases, the fuel injection volume decreases, and the fuel injection time lags, making it difficult to start the diesel engine. When the fuel injection time is delayed too much, the diesel engine cannot even run, and the needle valve installation should be replaced at this time.


D. Oil spray nozzle

Fault phenomenon: When the temperature of the diesel engine is low, it is difficult to start, the exhaust pipe emits white smoke, and the diesel engine becomes black smoke after the temperature rises. And high fuel consumption.

Failure analysis: When the injector is working, the sealing cone surface of the needle valve body will be subjected to frequent strong impact of the needle valve, coupled with the continuous high pressure fuel injection from this place, the cone surface will gradually wear or spots, resulting in fuel injection Drip oil. When the temperature of the diesel engine is low, the exhaust pipe emits white smoke, and after the temperature of the diesel engine rises, it becomes black smoke. Check whether the movement of the needle valve is flexible, the cone surface should be free of wear and tightness, then, you need to replace the new injection nozzle installation.


E. The oil return is too high

Fault phenomenon: reduce the injection pressure, postpone the injection time, reduce the engine power, and even cause the diesel engine to stall.

Failure analysis: When the needle valve installation is worn seriously or the needle valve body and the injector housing are not tightly matched, the oil return of the injector will increase significantly. At the same time, the valve plate should also be noted As a result, the fuel return of the injector is too large, which affects the engine performance.


In order to avoid abnormal damage to the fuel injector, it is necessary to change the oil according to the season and maintain the diesel filter regularly. Avoid using inferior fuel and inferior filters, and also need to avoid the engine running for a long time. At the same time, it should be pointed out that the common rail system is a high-pressure system. Please do not disassemble it without permission to avoid injury. The fuel injector is a precision component.


Conclusion: Fuel Injector Replacement & Price


Then, if you found that your car fuel injector was broken, the first suggestion is to go to the professional maintenance point for maintenance. But if you want to try to repair it by yourself, I can give you some tips for fuel injector replacement. Installation steps are as below:


(1) Remove the upper body of the intake branch pipe.

(2) Remove the fuel injection pipe with an open ring wrench 3035.

(3) Unscrew the fastening nut, remove the bracket, and remove the fuel injector.

(4) Replace the heat insulation pad between the injector and the cylinder head.

(5) Install a new fuel injector.

(6) Check the base and install the injector correctly on the cylinder head.

(7) Install the bracket, the tightening torque of the bracket bolt is 20N·m.

(8) Install the fuel injection pipe with a tightening torque of 25N·m.

(9) Install the upper body of the intake branch pipe.


As one of the biggest car fuel injector manufacturers in China, DEFUS can provide the auto parts to many brands of cars, including Toyota, Ford, Nissan, Audi, Chrysler, Mazda, Honda, etc. And we accept customization. If you are searching for the replacing fuel injector, please watch our website and we will give you the favorable price.

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