The Structure Principle of Automobile Fuel Injector, the Fault Phenomenon of Fuel Injector

What is a car fuel injector? I believe everyone has a common question in it. The fuel injector is a very important part of the gasoline EFI device. It controls fuel injection. If something goes wrong, it will affect the normal operation of the engine and will make the engine unnormal or stop immediately. According to the structure of the fuel injection port, the fuel injector can be divided into two types: shaft needle type and hole type. Let’s take a look at the structural principle of the car’s fuel injector with me.

Structural Principle of Automotive Injector—Introduction

fuel injector

The fuel injector is a key part of the car’s electronic fuel injection device. It controls the final fuel injection. If something goes wrong, the engine will not work properly or stop working immediately. If the fuel injector is installed at the position of the original carburetor and is combined with the throttle valve, this form is called a single-point electronically controlled fuel injection. Its advantages are low cost and simple maintenance. The unequal distance leads to uneven fuel distribution, and the fuel easily adheres to the wall of the intake pipe when the cold engine is started.

If the fuel injector is installed on the intake pipe of each cylinder, this form is called the multi-point electronically controlled fuel injection device, which is the form currently adopted by most gasoline-electric injection engines. Its advantage is that each cylinder has its own fuel injector. The fuel injector is as close as possible to the intake valve, avoiding the shortcomings of single-point electronically controlled fuel injection. The disadvantage is high cost and complicated maintenance. At present, most automobile engines use multi-point EFI, and a small number of economic vehicles use single-point EFI. If the old fuel injector engine is converted to an electronic injection type, a single-point electronic injection type is used.

General automobile electronically controlled gasoline injection device consists of three parts: fuel supply part, gas supply part and control part. The fuel supply part is composed of a fuel tank, gasoline pump, gasoline filter, pressure regulator and fuel injector. The gasoline pump draws gasoline from the fuel tank and filters impurities through the gasoline filter. The negative pressure of the intake manifold is sent to the injector of each cylinder through the oil pipe. The injector is equivalent to a switch, the part that controls the switch is the ECU.

The fuel injector is controlled by the solenoid, and the on-off of the solenoid current is controlled by the ECU. The ECU processes the signal fed back by the sensor and sends an electrical signal to the fuel injector. This electrical signal determines the time when the fuel injector is turned on and the gasoline is injected. This time interval is called the “pulse width” of the fuel injector. After the solenoid coil of the injector is energized, it generates a magnetic field. Under the action of the magnetic field, the plunger is sucked up against the spring force and takes the valve body away from the valve seat. Gasoline is ejected from the nozzle port under pressure; when the solenoid coil is de-energized, the magnetic field It disappears, the plunger moves down under the force of the spring, the valve body closes the nozzle port against the valve seat, and the gasoline can’t get out. The valve body is divided into two types: a ball valve and a needle valve. In order to ensure the accuracy of the fuel injection, the ball valve or the needle valve and the valve seat are required to have a high processing accuracy, and the lift of the valve body is small, only about 0.1 mm. Due to the role of a pressure regulator, the front of the injector is a high-pressure fuel path, and the rear is the low pressure of the intake manifold. The pressure difference forms a negative pressure to ensure that the fuel is sprayed into the vicinity of the intake valve.

The structural principle of automobile fuel injector-inspection methods of fuel injector

fuel injector

  1. When the starter drives the engine to rotate, use a long handle screwdriver or stethoscope to listen to whether the injector has a “click, click” working sound. Use the method of unplugging and plugging the injector harness connector to identify whether the injector is working.
  2. If the fuel injector does not work, a test light can be connected to the harness connector of the fuel injector to start the engine. If the test light flashes, it indicates that the injector control system is working properly, and the fault is in the injector. For the inspection of the fuel injector, a multimeter should be used to measure the resistance value of its electromagnetic coil. The resistance value is normal, indicating that the injector is blocked (affected by the carbon deposits generated during combustion and the gum in the fuel. This phenomenon is most common), the needle valve is stuck, etc., the injector should be repaired, cleaned or replaced; If it is normal, the fuel injector must be replaced.
  3. If the test light does not work, it means that the control system or circuit of the fuel injector is faulty. In this regard, you should first check whether the related lines of the fuel injector are intact, and only after ensuring that the external lines are good, can you determine that the computer is defective.

The structural principle of automobile fuel injector-maintenance of fuel injector

Fuel injector

The injector should be checked and adjusted once after working for about 700h. If the opening pressure is lower than the specified value of 1Mpa or more, or the carbon deposit on the head of the needle valve is serious, the needle valve should be removed and put into clean diesel oil to scrape off the carbon deposit with wood chips. The injection pressure difference of each cylinder of the same machine must be less than 1Mpa. In order to enable the diesel fuel injected into the cylinder by the fuel injector to burn completely in time, the fuel supply time of the fuel pump must be checked regularly. If the fuel supply time is too early, the vehicle will have difficulty in starting and failure of knocking the cylinder; if the fuel supply time is too late, it will cause black smoke in the exhaust, the engine temperature will be too high, and fuel consumption will increase. The fitting precision of the needle valve coupler of the injector is extremely high, and the hole diameter of the injection hole is very small, so the clean diesel oil of the specified brand must be selected strictly according to the seasonal changes, otherwise, the injector will not work properly.

Do not collide with other hard objects when cleaning the needle valve assembly of the fuel injector, and do not let it fall to the ground to avoid bruising. When replacing the needle valve coupler of the injector, the new coupler should be immersed in hot diesel oil at 80 ℃ for about 10 s to allow the anti-rust oil to fully melt, and then the needle valve should be pumped back and forth in the valve body in clean diesel, Wash thoroughly, so as to avoid the trouble of sticking to the needle valve due to the melting of the anti-rust oil when the injector is working.

Whether the fuel injector can work normally depends on whether we maintain it properly. Check whether the fuel injector is injecting oil: when the oil pump works normally, check the fuel injector. Start the engine and touch the fuel injector with a stethoscope to hear the sound of work. No sound, the fuel injector does not work. Then use a high-impedance test light, connect it to the harness connector of the fuel injector, and start the engine. If the test light is on, it indicates that the control circuit of the fuel injector is normal. If the fault is in the fuel injector, it should be replaced. If the test light is off, the fault is in the injector control circuit. I hope that the relevant information I shared about the structural principles of automobile fuel injectors can help buyers and your customers.

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