The fuel injection nozzle used in automobiles is actually a simple solenoid valve. When the solenoid coil is energized, a suction force is generated, the needle valve is sucked up, and the nozzle is opened. Fuel is sprayed at a high speed through the annular gap between the needle and the nozzle at the head of the needle valve, forming a mist shape, which is conducive to full combustion.Previously, the fuel injection nozzle used in diesel engines was mechanically controlled, and the mechanical diesel nozzle worked by controlling precision coupling parts (needle valve, needle valve body).The nozzle coupling is one of the three precision couplings of the traditional diesel engine. The three precision couplings are plunger, plunger sleeve, needle valve, needle valve body, oil outlet valve and oil outlet valve seat.The gasoline engine nozzle is a part of the electronic control system of the gasoline engine, replacing the carburetor of the carburetor gasoline engine.The nozzles used for automobiles mainly include diesel nozzle, gasoline nozzle, natural gas nozzle, etc. Now some foreign manufacturers can manufacture special nozzles for hydrogen.
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 normally open valve means that the valve is always open when no control signal is input), which is controlled by a valve needle moving up and down.WhenECUWhen the fuel injection command is issued, the voltage signal will make the current flow through the coil in the fuel injection nozzle, and generate a magnetic field to suck up the valve needle, so that the valve can be opened so that the fuel can be ejected from the fuel injection hole.The biggest advantage of injection 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 its exhaust gas can meet the specifications of environmental protection laws and regulations.
Effect of carbon deposition
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AsEFI engineOne of the key components of the fuel injection nozzle, its work will seriously affect the performance of the engine.Blockage of fuel injection nozzle will seriously affect vehicle performance.The reason for the blockage is that carbon deposits on the fuel injection nozzle in the engine or impurities in the fuel block the fuel injection nozzle path.After a car has been driven for a period of time, certain deposits will form in the fuel system.The formation of deposits is directly related to the fuel of the car: first, because the gasoline itself contains colloid and impurities, or dust and impurities brought in during storage and transportation, accumulated deposits similar to sludge are formed in the fuel tank, fuel inlet pipe and other parts of the car;Secondly, the unstable components in gasoline react at a certain temperature to form colloid and resin like viscous substances.When these viscous substances are burned in the fuel injection nozzle, intake valve and other parts, the deposits will become hardCarbon deposit。
Fuel injection nozzle
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 sediments.Deposits in the fuel system are very harmful.Deposits will block the needle valve and valve hole of the fuel injection nozzle, affect the working performance of the precision components of the electronic injection system, and lead to a decline in power performance;Deposits will form carbon deposits on the intake valve, which will lead to untight closing, unstable idling of the engine, increased fuel consumption and worsening exhaust emissions;The deposits will form hard carbon deposits on the piston crown, cylinder head and other parts. Due to the high heat capacity of carbon deposits and poor thermal conductivity, it is easy to cause engine shock and other failures;In addition, the service life of three-way catalytic converter will be shortened.
The quality of the fuel injection nozzle plays a fundamental role in the power of each engine.Due to poor fuel, the fuel injection nozzle does not work properly, causing serious carbon deposition in the cylinder;Accelerated wear of cylinder barrel and piston ring will cause unstable idle speed, increased fuel consumption, weak acceleration, difficult starting and excessive emissions. In serious cases, the fuel injection nozzle will be completely blocked and the engine will be damaged.Therefore, it is necessary to clean the nozzle regularly. If the nozzle is not cleaned for a long time or frequently, it will cause bad effects.
As for the cleaning time, it should be determined according to the condition of the car and the quality of the fuel normally added. Generally speaking.Good vehicle condition and good fuel quality can be extended to about 40000~60000 km.When the fuel injection nozzle is slightly blocked, the vehicle condition will also be affected.Sometimes such a fault occurs: the car shakes when it is in first gear and starts. When it is in high gear and accelerates, such a phenomenon disappears. Assuming that various sensors on the car work 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 in high gear, it is possible that the slight glue is sprayed away (dissolved), and the car's performance is restored.In such a slight blockage of the fuel injection nozzle, it is generally unnecessary to clean it.Because the slight colloid can be dissolved.Therefore, in daily driving, you should always run at a high speed to reduce the possibility of carbon deposition.When the fuel quality of the vehicle is poor or the driving time is long, if the fuel injection nozzle is not cleaned for a long time, this blockage will be more serious, which will cause poor fuel injection, poor fuel injection angle and atomization of the engine, resulting in poor operation of the engine at idle speed, acceleration or full load conditions, resulting in reduced engine power, increased fuel consumption and increased emission pollution,Even make the engine unable to work.Therefore, the fuel injection nozzle should be cleaned and tested carefully on a regular basis to ensure that it works well.
clean
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When cleaning is required, specific choices are needed - control of fuel injection quantity: for the same type of EFI vehicle, the pressure of the gasoline pump is constant, regardless of the throttle opening, as long asFuel pressure regulatorThe pressure of the fuel injection nozzle is always constant.The fuel injection nozzle is strictly used together with the fuel pump and the fuel pressure regulator. Only the designed pressure can achieve the best atomization effect. The pressure is lower than the design pressure, and the oil sprayed is not foggy, columnar, and should not be mixed with air;If the pressure is too high, the oil ejected is conical and difficult to mix, and the injection force is too large, so a lot of fuel is directly injected into the pipe wall, which directly affects the mixing ratio parameters.
The pressure should be constant whether accelerating or idling.The pressure of different models is also different (a friend mentioned that the selection of several gears of the cleaning machine is actually the pressure selection for different models, not the different pressure for accelerating idle speed, incorrect selection of the injection pressure, and poor atomization of the injection nozzle).The amount of fuel injection depends on the duration of fuel injection.According to the control mode of solenoid coil, fuel injector can be divided into voltage driven type and current driven type.Voltage type also includes low resistance andHigh resistanceThe high resistance can be connected to 12V, while the low resistance can only be connected to low voltage. If it is connected to 12V wrongly for a long time, the coil will burn.During fuel injection, the voltage provided by the computer is constant, for example, 12V. When fuel is cut off, the voltage changes to 0V immediately. This change is instantaneous, likeComputer languageThere is no such thing as 0.5 between 0 and 1.In other words, this is a pulsating DC electrical signal, not a term like AC, etc.What is the concept of AC?Alternating current is only called alternating current.It seems that in the car, except for the part before the generator rectifier, there is basically no AC contact.When the fuel injection nozzle is blocked, the fuel injection is not smooth, or there are carbon deposits and glues in the gap between the fuel injection nozzles, and the designed fuel injection volume or atomization effect cannot be reached, then cleaning is required.[1]
Troubleshooting
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Orifice blockage
The needle can be used for dredging, and after dredging, it should be carefully cleaned.The large plane of the needle valve body is in poor contact with the plane of the main body of the fuel injection nozzle, or the cylindrical surface of the needle valve is severely worn.If the large plane of the needle valve body is in poor contact with the plane of the main body of the fuel injector, chrome oxide can be coated on the flat plate for "8" grinding;If the cylindrical surface of the needle valve is severely worn, the needle valve couple shall be replaced in pairs.
Poor sealing
The needle valve and needle valve body are poorly sealed, resulting in poor atomization or oil dripping of the fuel injection nozzle.
This kind of fault can be coated on the sealing belt at the needle valve end with fine chrome oxide or toothpaste, but never on the cylindrical part, and then insert the needle valve into the needle valve body, knocking and rotating until it is closed.Chrome oxide or toothpaste must be washed off after grinding.
With air
There is air in the oil circuit.Just exhaust the air in the oil circuit.
Poor oil supply
The fuel transfer pump needs to be overhauled.If the oil pipe joint leaks, try to connect it to prevent it from leaking.
Insufficient elasticity
The force of the piston spring is insufficient or the spring is broken.The spring should be replaced.
Piston wear
Piston wear affects oil supply.Replace the piston.
Causes of jamming
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Farmers who have used diesel generators generally know that the fuel injection nozzle is one of the three pairs of precision parts in the fuel supply system of diesel engines.Its normal service life is more than 1000 hours.However, due to improper use, it is often worn and stuck after hundreds of hours or even dozens of hours.
1、 Main reasons for stuck fuel injection nozzle:
1. The diesel oil is not clean, and there are impurities in the high-pressure oil pipe, which makes the needle valve couple not closed tightly, and the high-pressure gas in the combustion chamber flows back, burning the needle valve couple.In addition, the dirt on the pressure regulating spring, tappet and other parts of the injector moves to the upper part of the injector needle valve through the injector tappet, or the cotton rope and lead wire used to prevent oil leakage on the oil circuit enters the injector through the high-pressure oil pipe, which will cause the needle valve couple to be stuck.
2. The engine temperature is too high, and the fuel injector is poorly cooled, causing the delivery valve couple to jam.However, too late oil supply time, too much or blocked scale in the cooling channel, wear on the end face of the water pump impeller, long-term overload of the engine, etc. will make the engine overheat.
3. The outlet valve is worn, which makes the fuel injector drip when stopping fuel injection, so as to cause the fuel injector to burn coke and deposit carbon, resulting in a stuck fault.
4. During the installation of the fuel injector, the gasket was missing or damaged, resulting in air leakage, which caused the local temperature of the fuel injector to be too high and stuck.
5. The injection pressure is too low, resulting in the reverse channeling of high-pressure gas in the combustion chamber;
6. Parts manufacturing reasons, such as the fitting between the injector mounting hole on the cylinder head and the injector is too tight, the clearance between the needle valve body and the mounting hole on the cylinder head is too small, and the cylinder head injector mounting hole is too deep.
Fuel injection nozzle
2、 Repair method for stuck fuel injection nozzle: first put the stuck fuel injection nozzle into diesel or engine oil for heating, then take it out and wrap it with cloth, then clamp the needle valve with pliers and slowly move it, and take the needle valve out of the needle valve body.Drop a small amount of clean engine oil into the needle valve body to make the needle valve repeatedly move 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 grinding paste.Pay attention to the amount of grinding paste and grinding time when grinding.Install the cleaned bell valve couple onto the injector, and adjust the injection pressure before reuse.
Fuel consumption reason
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During the use of the diesel generator set, some customers reported that the fuel consumption of the set was too fast, but they did not know which part to start with. Now Fengde will analyze several situations for you:
1、 When excessive oil consumption is found, first check whether there is oil leakage at the connection between the engine body and the gear housing cover, the large plate, the rear cover, and the cover at the side of the traveling wheel.In case of oil leakage, observe whether the sealing gasket at each connection part is complete, and replace the damaged sealing gasket.If the sealing gasket is complete, check whether the connecting screws of each part are loose.The loose bolts can be tightened to the specified torque with a wrench.If the above parts are basically normal, and the oil leakage is at the rack position, the oil shell should be checked. The main inspection part is at the front end of the oil shell side on the same side as the traveling wheel. Most of the engine base screws are loose, and the traveling wheel has a long-term collision with the rack angle iron protecting the oil shell under the pull of the V-belt, and the oil shell is worn through to form a gap, resulting in oil leakage.
2、 The normal wear caused by the long-term use of the engine or the abnormal wear caused by improper maintenance will cause the cylinder liner of the diesel engine to form a longitudinal stretch mark, the cylinder diameter and the piston side clearance exceed the specified value, which will reduce the supporting force of the piston ring accordingly, and lead to the phenomenon of dirty oil scraping.Or because the internal support torsion spring in the oil ring is disconnected at the opening position of the oil ring, resulting in dirty oil scraping and participation in combustion, resulting in serious oil consumption symptoms, which are manifested in difficulty in starting the diesel engine, obvious blue smoke from the exhaust pipe, and serious fuel injection of the respirator.Moreover, on the side of the piston that should be upward, the combustion chamber will be inverted due to the inverted direction during assembly. Although it will not affect the starting of the diesel engine, the oil consumption will be quite serious, with a daily oil consumption of about 0.5kg.
Fuel injection nozzle
3、 If the valve guide is severely worn, it will also burnDiesel generatorAlthough the situation of group A engine oil is rare, according to the introduction of relevant information, it is also a reason that cannot be ignored.
Troubleshooting
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According to the inspection steps for leakage in the injection pump of the diesel generator, the following steps are taken:
1. See if the seat is not tight, and if the tight seat is searching for leakage.
2. First of all, let's go to the oil pump, open the pump cover, start the small throttle, the engine runs, and see the internal leakage of the fuel pump.If the surface of the cylinder piston and plunger scapula is greasy, it can be observed that the drop of the oil flows to the small bubble roller mechanism.Further review the vane surface washer plunger, plunger defect or wear.
3. If there is no foam, you should consider the problem of the fuel pump in the secondary.Users are allowed to prepare and put 3-4 kilograms of diesel into the container, remove the fuel pump assembly, screw in the pipe fuel pump after removing the hollow screw, connect the inlet of the fuel pump to the water pump, and the port will be blocked. When one person's morale is high, one person will put into the diesel pump, and soon find the place where the oil leaks.The method has been applied to the head of pressure test pump.Before the pressure test pump head, the position of the plunger should be adjustable to stop the oil, that is, the plunger can be tilted to avoid returning to the hole.Until the leakage part is found out.
Check the reason for the troubleshooting method
1. Loose fastener of valve seat 6-8 kg force
2. The clearance of the fuel pump will be placed on a large or partially replaced grinding or oil replacement seal for the fuel pump
3. The pressure side of shoulder pad shall be assembled.Replace the shoulder pad surface with a new one
4. The plunger and plunger are seriously worn during replacement
5. Cracked or uneven surface of shoulder plunger sleeve.Replace the plunger pair
Fuel injection nozzle
6. Upper body and trachoma or replace defective upper body[2]
