Introduction of fuel injector

The fuel injector is actually a simple solenoid valve. When the electromagnetic coil is energized, the suction force is generated, the needle valve is sucked up, the nozzle hole is opened, and the fuel is ejected at high speed through the annular gap between the shaft pin at the head of the needle valve and the nozzle hole, forming mist, which is beneficial to full combustion.

Basic introduction of fuel injector

The injector itself is a normally closed valve (normally closed valve means that the valve is always closed when there is no control signal input; Normally open valve means that when there is no control signal input, the valve is always open, and the valve needle moves up and down to control the opening and closing of the valve. When the ECU sends the fuel injection instruction, its voltage signal will make the current flow through the coil in the fuel injector, generate a magnetic field to attract the valve needle and open the valve, so that the fuel can be ejected from the fuel injection hole. The biggest advantage of jet fuel supply is that the control of fuel supply is very accurate, so that the engine can have the correct air-fuel ratio in any state, which not only keeps the engine running smoothly, but also conforms to the norms of environmental protection laws and regulations.

Nozzle carbon deposition and its influence

As one of the key components of EFI engine, the performance of injector will be seriously affected. Nozzle blockage will seriously affect the performance of the car. The reason for the blockage is that carbon deposits in the engine are deposited on the fuel nozzle or impurities in the fuel block the fuel nozzle channel. After the car runs for a period of time, the fuel system will form certain deposits. The formation of deposits is directly related to automobile fuel: firstly, because gasoline itself contains colloid and impurities, or dust and impurities brought in during storage and transportation, deposits similar to sludge are formed in automobile fuel tanks and oil intake pipes over time; Secondly, the unstable components in gasoline react at a certain temperature to form colloid and resin-like viscous bodies. When these viscous substances are burned in the nozzle, intake valve and other parts, the deposits will become hard carbon deposits.

Carbon deposition in injector and its influence

In addition, due to urban traffic congestion, cars are often at low speed and idle speed, which will aggravate the formation and accumulation of these deposits. The deposits in the fuel system are very harmful. Deposits will block the needle valve and valve hole of injector, affect the working performance of precision parts of EFI system, and lead to the decline of dynamic performance; Deposits will form carbon deposits in the intake valve, which will lead to the untidy closing of the intake valve, unstable idle speed of the engine, increased fuel consumption and deterioration of exhaust emissions; Deposits will form hard carbon deposits on the piston crown and cylinder head, which is easy to cause engine failure due to its large heat capacity and poor thermal conductivity. In addition, it will shorten the service life of the three-way catalyst. The work of injector plays an important role in the power of each engine. Due to poor fuel, the injector does not work normally, resulting in serious carbon deposition in the cylinder; The accelerated wear of cylinder and piston ring will cause unstable idle speed, rising fuel consumption, weak acceleration, difficult start-up, excessive emission, complete blockage of injector and damage to engine.

Carbon deposition in injector and its influence

Therefore, it is necessary to clean the nozzle regularly. Long-term non-cleaning or frequent cleaning of the nozzle will have a bad influence. As for the cleaning time, it depends on the condition of the car and the quality of fuel added at ordinary times. Generally speaking, it is recommended that most users clean it once every 20,000 ~ 30,000 km. The car is in good condition and the fuel quality can be extended to about 40,000 ~ 60,000 kilometers. When the injector is slightly blocked, it also has a certain impact on the vehicle condition. Sometimes, there will be such a fault: the car is a little shaky when it starts in first gear, and it disappears when it accelerates in high gear. Assuming that all kinds of sensors on the car are working normally, the throttle is clean and the circuit is normal, it is likely that the fuel injector is slightly blocked.

However, when accelerating in high gear, slight gum may be sprayed away (dissolved) again, and the performance of the car will be restored. This slight blockage of the fuel nozzle can usually be avoided. Because slight gum can be dissolved. Therefore, in daily driving, you should always run at high speed to reduce the possibility of carbon deposition. If the fuel injector is not cleaned for a long time, the blockage will be more serious when the gasoline quality is poor or the vehicle runs for a long time, resulting in poor fuel injection, poor fuel injection angle and atomization, poor engine performance at idle speed, acceleration or full load, reduced engine power, increased fuel consumption, aggravated emission pollution, and even made the engine unable to work. Therefore, the nozzle should be carefully cleaned and inspected regularly to ensure its good work.

Maintenance of choke

Cleaning nozzle

When cleaning is needed, it is necessary to choose the specific time-the control of fuel injection quantity: for the same type of EFI vehicle, the pressure of the gasoline pump is constant, and the pressure of the injector is always constant as long as it is adjusted by the fuel pressure regulator, regardless of the throttle opening. The fuel nozzle is strictly matched with the fuel pump and fuel pressure regulator. Only under the designed pressure can the fuel nozzle achieve the best atomization effect. The pressure is lower than the design pressure, and the sprayed oil is not in the form of fog, but columnar, and should not be mixed with air. When the pressure is too high, the sprayed oil is conical and difficult to mix. Moreover, the injection force is too large, and a lot of fuel is directly sprayed on the pipe wall, which directly affects the mixing ratio parameters.

Cleaning nozzle

Whether it is accelerating or idling, the pressure should be constant. The pressure of different models is also different (some friends said that the choice of several gears of the cleaning machine is actually the choice of pressure of different models, not the different acceleration idle pressure, the wrong choice of injection pressure and poor nozzle atomization). The amount of fuel injected depends on the length of fuel injection time. Fuel injectors are divided into voltage-driven type and current-driven type according to the different control modes of electromagnetic coils.

Voltage type can also be divided into low resistance type and high resistance type. High resistance can be connected to 12V, and low resistance can only be connected to low voltage. If you connect 12V wrongly for a long time, it will burn the coil. When the fuel is injected, the voltage provided by the computer is constant, such as 12V, which immediately becomes 0V when the fuel is cut off. This change is instantaneous, just like the concepts of 0 and 1 in computer language, there is no concept of 0.5 in the middle. In other words, this is a pulsating DC signal, not a noun like alternating current. What is the concept of alternating current? Positive and negative interleaving is called alternating current. It seems that except for the part in front of the generator rectifier, there is basically no contact with alternating current. When the nozzle is blocked, the fuel injection is not smooth, or there is carbon deposit and colloid in the nozzle gap, which can not reach the designed fuel injection quantity or atomization effect and needs to be cleaned.

trouble clearing

1. Nozzle blocked

It can be dredged with a needle, and the warp and weft should be carefully cleaned after dredging. The large plane of needle valve body is in poor contact with the plane of injector body, or the cylindrical surface of needle valve is seriously worn. If the large plane of needle valve body is in poor contact with the plane of injector body, chromium oxide can be coated on the flat plate for figure 8 grinding; If the cylindrical surface of the needle valve is seriously worn, the needle valve couples should be replaced in pairs.

trouble clearing

2. Poor sealing

The needle valve and needle valve body are poorly sealed, resulting in poor atomization of the nozzle or oil dripping.

This kind of fault can be coated with fine chromium oxide or toothpaste on the sealing belt at the needle end, but never on the cylindrical part. Then insert the needle valve into the needle valve body and turn it while knocking until it is tightened.