I. Types and Causes of Vulnerable Faults of Injectors

Vulnerable faults of injectors in electronically controlled fuel injection system can be divided into mechanical faults and circuit faults.

(1) Mechanical failure

Mechanical failure is characterized by mechanical action failure caused by stuck, blocked and leaked fuel injectors, which leads to engine working condition damage and seriously affects the normal use of automobiles.

1. The fuel injector is stuck. The fault is that the engine ECU sends out the fuel injection signal, and the electromagnetic coil of the fuel injector generates magnetic attraction after being electrified. Because the gap between the needle valve and the valve seat is blocked by the residual glue, the lifting action of the oil suction plunger becomes unsmooth, and the prescribed needle valve opening speed cannot be reached, which affects the normal fuel injection quantity. After the fuel injector is stuck, the engine has the symptoms of unstable idle speed, difficult starting and poor acceleration performance. The main reason why the injector is stuck is the use of inferior gasoline. Paraffin and colloid in inferior gasoline will cause the injector to jam in a short time, which will lead to early engine failure.

2. The fuel injector is blocked. Faults can be divided into two situations: internal blockage and external blockage. The reason of internal blockage is that impurities and dirt mixed in gasoline block the movement gap inside the injector, which makes the mechanical action of the injector invalid. The reason of external blockage is that the injection port outside the fuel injector is blocked by carbon deposit and dirt, which leads to the failure of injection work of the fuel injector. After the fuel injector is blocked, the engine is difficult to start, unstable in operation, idling and flameout, the acceleration performance becomes worse, and even the engine chatters, resulting in abnormal wear and deterioration of parts. Due to the different degree and situation of injector blockage, the symptoms of early engine failure are also different.

3. The fuel injector leaks. Faults can be divided into two situations: internal leakage and external leakage. Internal leakage is due to the premature wear of the injector in use, which leads to the injector constantly leaking gasoline into the intake manifold under the pressure of the pressure oil circuit. The external leakage is located at the joint of the fuel injector and the pressure oil pipe. Gasoline leaks out of the intake manifold, and oil drops are on the cylinder block. They evaporate in the fume hood when heated. Once there is a spark of circuit leakage, it will cause a fire at any time. When the fuel injector leaks, the fuel consumption of the engine increases obviously, the dynamic performance of the engine deteriorates, and the HC value of the exhaust gas increases.

(2) Circuit failure

The circuit fault of the injector itself is mainly manifested in the electromagnetic coil, which can be summarized as coil open circuit, coil short circuit and coil aging.

1. The solenoid is open. The fuel injection condition of the injector with blown electromagnetic coil is interrupted, which leads to the failure of the engine. The main reason of coil burning is that the wiring is changed blindly during maintenance, which leads to wiring error and the coil insulation layer is burned out. In addition, in the maintenance of cleaning the injector, because the operator is unfamiliar with the knowledge of electromagnetic coil resistance, the injector with lower resistance is mistakenly connected to the battery power supply, which leads to the overload of coil current, heating and ablating the insulated layer of the enameled wire of the coil, and even burning the wire of the coil seriously.

2. The electromagnetic coil is short-circuited. Electromagnetic coil short circuit refers to the pulse control current that normally appears in the electromagnetic coil of the fuel injector, and it flows through a short line without a specified line. After the short-circuit fault occurs, as long as the ignition switch is turned on, the fuel injector will always inject fuel. When starting the engine, the spark plug is flooded because there is too much oil to start it. Even if the engine can barely start, the operating conditions of the engine are extremely deteriorated, the fuel consumption is too high and the mixture is too rich, which leads to deflagration and engine wheezing, resulting in increased mechanical wear.

Second, the prevention and control measures of vulnerable faults of fuel injectors

(A) mechanical failure prevention and control measures

As the fuel of electronically controlled engine, gasoline should strictly abide by the gasoline label and quality specified in the instruction manual, pay attention to cleanliness when filling, and try to choose unleaded gasoline that meets the specified standards. If it is difficult for local gas stations to ensure the above conditions, they should try to use high-grade gasoline and add gasoline additives with cleaning and sol functions to the fuel tank every quarter to improve their quality and performance. In the process of automobile use, the fuel filter should be replaced in time in strict accordance with the prescribed mileage.

For the stuck and blocked injectors, clean them with mixed solution in time to avoid more serious mechanical damage caused by the car driving with disease. Attention should be paid to the resistance type of injector when cleaning. The high-resistance injector can be directly connected with the battery, and the low-resistance injector must be connected in series with the battery, with a resistance of10Ω-20Ω, so as not to burn out the electromagnetic coil. If the special cleaning equipment for fuel injection system is used, the cleaning effect will be better. For fuel injectors blocked by carbon deposits and dirt, scraping method can be used to clean them.

The leakage fault of the injector will be directly reflected in the working state of the engine, and the leakage position should be found in time. The simplest method is to take down the injector, observe whether there is oil dripping, and check the external leakage faults one by one. Once the leakage is found, it should be stopped in time, and it must not be taken lightly, so as not to cause a car fire accident.

(2) Prevention and control measures of circuit failure

The fuel injector should keep the circuit system clean during use, and it is forbidden to change the connection mode of the circuit at will. Do not use knocking vibration when removing the fuel injector to avoid damaging the internal electromagnetic coil. When removing the wire connector, turn off the ignition switch first to prevent instantaneous overvoltage from burning the electromagnetic coil and electronic devices inside the engine ECU. When overhauling the fuel injector circuit, a high impedance digital multimeter or a microcomputer fault analyzer should be used, and ignition is strictly prohibited to avoid burning the fuel injector control circuit of the engine ECU.

When detecting the fault of the fuel injector circuit, you can use the stethoscope when the engine is idling. If the needle valve seating sound with the same frequency, the same interval and the same sound can be heard on each injector body, the sound is monotonous and uniform, indicating that the injector works normally. If the engine is found to be unstable and on fire, and there is no needle valve seating sound after auscultation, it should be removed and inspected to determine whether it is a mechanical fault or a circuit fault.

Practice shows that in the circuit failure of the fuel injector, the failure of the engine microcomputer control system has a high probability of causing the engine working condition to deteriorate, which is mainly manifested in the damage of various sensors and internal electronic devices of the engine ECU. Sensor fault is easy to judge and eliminate, but engine ECU fault is difficult to judge, which requires special instrument diagnosis, and maintenance must be carried out in a special maintenance station authorized by the manufacturer. When the sensor fails, the comparison method is often used in maintenance practice, that is, the sensor suspected of failure is removed and replaced with a sensor with good technical condition, and the performance of the two is compared to judge the failure. The fault of engine ECU itself is often manifested as the continuous deterioration of working state under certain working conditions, which can be diagnosed by simple voltage detection. Turn on the ignition switch, unplug the fuel injector connector, and test the voltage. One is 12v (fuel injector power cord) and the other is Ov (grounded after passing through the engine ECU). If the measurement results are not in conformity with the regulations, it is judged that the microcomputer control system of the engine is faulty. The fault of the electromagnetic coil of the fuel injector can be judged by detecting the resistance value. A resistance value of ∞ indicates that the coil is open, a low resistance value indicates a short circuit, and a resistance value much higher than the specified value indicates that the coil is aging.

When the engine can't start after the fault occurs, it will bring difficulties to find the fault. In practice, the method of segmentation recognition is often used to judge. First, turn on the ignition switch and check whether the electric fuel pump has running sound. If the sound is normal, you can cut off the power supply and install a fuel pressure gauge at the oil drain plug to detect the pressure of the electric fuel pump. When the pressure is lower than 200kPa, it is judged that the electric fuel pump is worn or damaged and should be replaced. If the pressure is normal, remove the fuel injector and connect the battery power supply with the matching test plug. The fuel injector should inject fuel. If there is no fuel injection, the oil supply system is faulty. If the fuel injection is normal, replace the fuel injector without connecting the wire connector, and intermittently contact the fuel injector pin with the temporary power cord of the test plug; At the same time, manually control the throttle and start the engine with the starter; As long as the throttle opening is appropriate, the intermittent rhythm of the stylus is appropriate, and the engine ignition system works normally, the engine will run at idle speed. If it doesn't start at all, there is something wrong with the ignition system. Continue to repair the ignition system fault.

I don't know if it is what you need. If you still need reference materials, please visit (59 168).