What Is a Jet Injector?

At present, the fuel injector for automobiles is actually a simple solenoid valve. When the solenoid coil is energized, a suction force is generated, the needle valve is sucked up, the injection hole is opened, and the fuel passes through the ring between the shaft needle on the needle valve head and the injection hole. The gap sprays out at high speed, forming a mist, which is conducive to full combustion. In the past, the fuel injection nozzles for diesel engines were controlled mechanically, and the mechanical diesel nozzles worked by controlling precision parts (needle valve, needle valve body). The nozzle parts are one of the three precision parts of the traditional diesel engine. The three precision parts are: plunger, plunger sleeve, needle valve, needle valve body, oil outlet valve, oil outlet valve seat. The gasoline engine nozzle is part of the gasoline electrical control system, replacing the carburetor of the carburetor type gasoline engine. Automotive nozzles are mainly diesel nozzles, gasoline nozzles, natural gas nozzles, etc. Now some foreign manufacturers can make special nozzles for hydrogen.

Chinese name: Injector

Foreign name: fuel spray nozzle
Principle: Simple solenoid valve

Injector definition

The fuel injection nozzle itself is a normally closed valve (normally closed valve means that the valve is always closed when no control signal is input; while a normally open valve is that the valve is always open when no control signal is input). A valve needle moves up and down to control the opening and closing of the valve. When the ECU issues an injection instruction, its voltage signal will cause a current to flow through the coil in the nozzle, generating a magnetic field to suck up the valve needle, and let the valve open so that the fuel can be ejected from the injection hole. The biggest advantage of injection fuel supply is that the fuel supply control 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 its exhaust gas can also comply with environmental protection regulations.

Impact of carbon deposits at the injector

As one of the key components of the EFI engine, its performance will seriously affect the performance of the engine. Blocked fuel injectors can severely affect car performance. The cause of the blockage is due to the deposit of carbon in the engine on the fuel injection nozzle or the blockage of the fuel injection nozzle passage due to impurities in the fuel. After the car has been driving for some time, a certain amount of deposits will form in the fuel system. The formation of deposits is directly related to the fuel of the car: firstly, because the gasoline itself contains colloids, impurities, or dust and impurities brought in during storage and transportation, oil-like sludge deposits are formed on the car's fuel tanks and oil inlet pipes Secondly, the unstable components in gasoline react at a certain temperature to form gum and resinous viscous substances. When these stickies are in the nozzles, intake valves, etc., when they burn, the deposits will become hard carbon deposits.

In addition, due to urban traffic congestion, cars are often at low speeds and idle speeds, which will aggravate the formation and accumulation of these deposits. Fuel system deposits are very hazardous. The deposit will block the needle valve and valve hole of the fuel injection nozzle, affect the working performance of the precision parts of the electronic injection system, and cause the power performance

Injector Deposits will form carbon deposits on the intake valve, causing it to close improperly, resulting in unstable engine idling, increased fuel consumption and worsening exhaust emissions; deposits will form hard deposits on the piston top and cylinder head, etc. Because of the high thermal capacity and poor thermal conductivity of coke deposits, it is easy to cause engine shock and other faults; in addition, it will shorten the life of the three-way catalyst.

The performance of the injectors plays a fundamental role in the power of each engine. Due to poor fuel, the injectors do not work well, causing serious carbon deposits in the cylinder; cylinder barrels and piston rings are accelerated to wear, resulting in unstable idle speed, increased fuel consumption, weak acceleration, difficult starting and excessive emissions. Grease nipple, damage the engine. Therefore, it is necessary to clean the fuel injection nozzles regularly. Long-term uncleaning or frequent cleaning of the nozzles will cause bad effects.

As for the timing of cleaning, it should be determined according to the condition of the car and the quality of the fuel added in general, generally speaking. Good vehicle conditions and good fuel quality can be extended to about 40,000 to 60,000 km. When the fuel injection nozzle is slightly blocked, it also affects the vehicle condition to a certain extent. Sometimes this kind of failure occurs: when the first gear is engaged, the car starts to shake, and when it is hung up, the phenomenon disappears when accelerating. It is assumed that the various sensors on the car are working normally, the throttle valve has been cleaned and the circuit is normal It is likely that the fuel injection nozzle is slightly blocked. However, when accelerating at high gears, it is possible that a slight amount of gum is sprayed away (dissolved) and the performance of the car is restored. In such a situation that the fuel injection nozzle is slightly blocked, cleaning is generally not required. Because slight gum can be dissolved away. Therefore, in daily driving, you should often run a high speed to reduce the possibility of coke formation. When the gasoline quality is poor or the vehicle runs for a long time, if the fuel nozzle is not cleaned for a long time, this clogging phenomenon will be more serious, resulting in poor fuel injection by the engine, poor injection angle and atomization, resulting in engine idling and acceleration Or, the engine does not work well at full load, which causes the engine power to decrease, fuel consumption to increase, emission pollution to increase, and even to make the engine inoperable. Therefore, the inspection nozzle should be carefully cleaned regularly to ensure that it works well.

Injector cleaning

When you need cleaning, you need to choose a specific option-how much fuel injection is controlled: the pressure of the gasoline pump is constant for the same type of EFI vehicle, regardless of the opening of the throttle valve, as long as it is adjusted by the fuel pressure regulator, the fuel is injected. Mouth pressure is always constant. The fuel injection nozzle is strictly used in conjunction with the fuel pump and fuel pressure regulator. Only the designed pressure can achieve the best atomization effect. The pressure is lower than the designed pressure. The sprayed oil is not misty and cylindrical. It should not be mixed with air; if the pressure is too high, the sprayed oil has a conical shape, and it is not easy to mix, and the spraying force is too large, and a lot of fuel is directly sprayed on the pipe wall, which directly affects the mixing ratio parameters.

Whether accelerating or idling, the pressure should be constant. The pressure of different models is also different (the gear selection of a washing machine mentioned by a friend is actually a pressure selection for different models, not a different pressure for accelerating idle speed. The fuel injection pressure was selected incorrectly, and the nozzle was atomized. bad). The amount of fuel injection depends on the length of the fuel injection time. According to the different control methods of the electromagnetic coil, the fuel injector is divided into two types: voltage-driven and current-driven. The voltage type is also divided into low resistance and high resistance. High resistance can be connected to 12V. Low resistance can only be connected to low voltage. Misconnection to 12V will burn the coil for a long time. During fuel injection, the voltage provided by the computer is constant, such as 12V, which immediately becomes 0V when the oil is cut off. This change is instantaneous, just like the concept of 0 and 1 in computer language. There is no 0.5 in the middle. In other words, this is a pulsating DC signal, not a term such as AC. What is the concept of alternating current? Positive and negative interleaving is called alternating current. It seems that in the car, except for the part before the generator rectifier, AC power is basically not accessible. When the fuel injection nozzle is blocked, the fuel injection is not smooth, or there is carbon deposit and glue in the gap between the fuel injection nozzles, and the designed fuel injection quantity or atomization effect cannot be achieved, so cleaning is required. ^[1]

Injector troubleshooting

Injector nozzle orifice blocked

You can use a needle to clear it, and clean it carefully after clearing. The large plane of the needle valve body is not in good contact with the plane of the nozzle body, or the cylindrical surface of the needle valve is worn. If the large plane of the needle valve body and the plane of the injector body are not in good contact, you can use chrome oxide to coat the plate for "8" -shaped grinding; if the cylindrical surface of the needle valve is worn, replace the needle valve pair.

Injector seal is bad

The needle valve and the needle valve body are not well sealed, causing poor atomization or dripping of the fuel injection nozzle.

This kind of trouble can use fine chromium oxide or toothpaste to apply on the sealing tape of the needle valve end, but do not apply to the cylindrical part, insert the needle valve into the needle valve body, and turn it until it is close. After grinding, chromium oxide or toothpaste must be washed away.

Injector has air

There is air in the oil circuit. Just remove the air from the oil circuit.

Poor fuel supply from the injector

The oil pump needs to be repaired. If there is a leak in the oil pipe joint, try to connect it so that it does not leak.

Insufficient elasticity of the injector

The spring of the piston spring is insufficient or the spring is broken. The spring should be replaced.

Worn injector piston

Piston wear affects oil supply. The piston needs to be replaced.

Causes of Injector Stuck

Farmer friends who have used diesel generators generally know that the fuel injector is one of the three pairs of precision components of the diesel fuel supply system. Its normal service life is over one thousand hours. However, due to improper use, it often wears out and gets stuck for hundreds of hours or even tens of hours.

First, the main reasons for the injector stuck:

1. The diesel oil is not clean. There are impurities in the high-pressure oil pipe, which will cause the needle valve parts to close tightly. The high-pressure gas in the combustion chamber will blow back and burn the needle valve parts. In addition, the dirt on the injector pressure regulating spring, tappet and other parts are moved to the upper part of the injector needle valve through the injector tappet, or the cotton rope and lead wire on the oil circuit to prevent oil leakage from entering the spray through the high-pressure oil pipe. Oiler will cause the needle valve coupler to get stuck.

2. The engine temperature is too high and the fuel injector is not cooling well, which causes the oil valve valve to be stuck. Too late oil supply time, too much scale or blockage of the cooling water channel, wear of the impeller end face of the water pump, and long-term overload of the engine will cause the engine to overheat.

3. The oil outlet valve is worn, which causes the oil dripping phenomenon when the injector stops injecting fuel, which causes the fuel injection nozzle to burn and deposit coke, which causes a stuck fault.

4. When the injector is installed, the missing gasket or gasket is damaged, causing air leakage and causing the local temperature of the injector to become too high and stuck.

5. The fuel injection pressure is too low, causing high-pressure gas in the combustion chamber to reverse.

6. Reasons for parts manufacturing, such as the tight fitting of the injector installation hole on the cylinder head with the injector, the gap between the needle valve body and the installation hole on the cylinder head is too small, the cylinder head injector installation hole is too deep, etc. .

Second, the repair method of the stuck injection nozzle: first put the stuck injection nozzle into diesel oil or engine oil to warm it up, then take it out and cover it with a cloth, then clamp the needle valve with pliers and slowly move the needle Remove the valve from the needle valve body. Put a small amount of clean engine oil into the needle valve body, and make the needle valve move repeatedly in the needle valve body until the needle valve can move freely in the needle valve body. If the sealing surface of the needle valve has burn marks, it should be ground with abrasive paste. When grinding, pay attention to grasp the amount of grinding paste and grinding time. Install the cleaned bell valve assembly on the fuel injector and adjust the fuel injection pressure before reuse.

Injector

Fuel consumption cause of injector

During the use of the diesel generator set, some customers reported that the fuel consumption of the unit was too fast, but they did not know which component to start with. Fengde will analyze several situations for everyone:

First, when excessive oil consumption is found, you should first check whether there is any oil leakage at the connection between the body and the gear room cover, the large disk on the side of the wheel, the rear cover, and the cover. If the oil leaks, pay attention to the integrity of the gaskets at each connection and replace the damaged gaskets. If the gasket is intact, check whether the connecting screws in all parts are loose. Use a wrench to tighten the loose bolts to the specified torque. If the above parts are basically normal, and the oil leakage is in the rack position, the oil casing should be inspected. The main inspection part is at the front end of the oil casing side on the same side as the row wheel. There is a long-term friction between the lower frame and the angle iron protecting the oil casing, and the oil casing is ground through to form a gap, resulting in oil leakage.

2. Normal wear caused by long-term use of the engine or abnormal wear caused by improper maintenance will cause longitudinal stretch marks on the cylinder liner of the diesel engine, and the cylinder bore and piston side clearance will exceed the specified values, which will reduce the support force of the piston ring accordingly. Small, the phenomenon of oil scraping is not clean. Or because the inner support twist spring in the oil ring is disconnected at the opening position of the oil ring, the oil scraping is not clean and participates in combustion, causing severe oil consumption symptoms, manifested as difficulty in starting the diesel engine, and obvious blue smoke from the exhaust pipe. , The respirator is seriously fuelling. In addition, the side of the piston that should have been turned upside down caused the combustion chamber to be turned upside down during assembly. Although the starting of the diesel engine will not be affected, the loss of oil will be very serious, and the fuel consumption will be about 0.5 kg per day.

Third, the valve guide wears severely and can burn diesel generator oil. Although rare, but according to the introduction of relevant information, it is also a cause that cannot be taken lightly.

Injector

Injector troubleshooting

The inspection steps based on the leakage in the injection pump of the diesel generator are as follows:

1. See if the valve seat is tense, and whether the tense seat is leaking like an African search.

2. First, let our body go to the oil pump, open the pump cover, start the small throttle, the engine is running, and we can see the internal leakage of the fuel pump. If the surface of the cylinder piston and plunger scapula oil is stained, the drop of the oil flow can be observed by the small bubble roller mechanism. Further examination of blade surface washer plunger, plunger defect or wear.

3. If there is no foam, you should consider the problem of the fuel pump on the vice. Allow the user to write 3-4 kg of diesel fuel into the container, remove the fuel pump assembly, remove the hollow screw and screw the fuel pump into the tube, and connect the fuel pump inlet to the water pump to block the port. Oil, when one person's morale, one person puts in diesel Press the pump and you will soon be able to find the place where the oil leaks. The method has been applied to the head of a pump which can also be tested. Before testing the pump head, the plunger position should be adjustable to stop the position against oil, that is, the plunger can be tilted to avoid back holes. Until the leak is identified.

Check the cause of the exclusion method

1.Seat tight tightening valve seat 6-8 kgf

2.The gap of the fuel pump will be placed in a large or part to replace the grinding or fuel pump and oil instead of sealing

3, assembled, the pressure side of the shoulder pad. Replace with new shoulder pad surface

4, plunger plunger replacement wear serious

5. Cracked or uneven surface of shoulder plunger sleeve. Replace the plunger pair

6. Upper body and trachoma or replacement of defective upper body ^[2]

Injector