V normal work the injection engine plays an important role in the injector. An injector is a simple device, but in fact it does a complex job on which the engine's operation depends. An electrovalve is located inside the injector, which, when voltage is applied to the ECU, opens the shut-off needle, and fuel in a certain proportion enters the cylinders
In most cases, the injector may not work due to the lack of voltage supply in the solenoid valve winding, there may be an open circuit, and the injector itself may be clogged, how can the injectors be cleaned. Determine the malfunction of the injector, you need to remove the connector from the injector one by one, the engine speed has dropped, then the injector is operational, there is no decrease in speed, then it is faulty. You can check with a tester and an LED light. We connect the tester to two terminals on the injector, if the reading is within 11-16 ohms, then the injector is suitable for operation, you can connect the injector terminals to the battery for a short time, then you will hear clicks when connecting.
We take the LED and connect it to the voltage supply connector to pins 1 and 2, and the engine turns with the starter, the LED should blink.
We check separately each terminal in the connector, with the ignition on, a positive voltage is supplied to the injector, if the engine is cranked with a starter, then the ECU supplies a negative voltage. To check the positive voltage, we connect one end of the LED to contact 1, and the other to ground, with the ignition on, the LED will be on, if not, look for an open circuit.
We check the negative contact, connect one end of the LED to contact 2 and the other to the positive of the battery through a light bulb, and when you scroll with the starter, the LED will flash, if not, look for an open circuit or the ECU is faulty.
Injectors- an actuator designed to spray fuel in the intake tract fuel system or in engine cylinders internal combustion... There are the following types of these devices - mechanical, electromagnetic, hydraulic, piezoelectric. Injectors for gasoline and diesel engines differ in the way they work. also in different brands car injectors work with different voltages and pressures. We will tell you about all this and much more in this material.
Types of nozzles
Let's characterize each of the listed types separately, and start with electromagnetic injectors... They are installed in gasoline engines... The injectors consist of the following component parts- solenoid valve, spray needle and nozzle.
Electromagnetic injection nozzle
Diesel electro-hydraulic nozzle
The principle of their work is quite simple. When a command is received from the vehicle's ECU, solenoid valve voltage is applied, due to which a magnetic field is created in it, which draws in the needle, thereby freeing the channel in the nozzle. Accordingly, fuel passes through it. As soon as the voltage on the valve disappears, the needle, under the influence of the return spring, closes the nozzle again and gasoline is no longer supplied to the cylinders.
Different voltages are supplied to injectors from different vehicle manufacturers. This must be taken into account when replacing and cleaning injectors.
The next type is electro-hydraulic nozzles... They are used in diesel engines, including those created by Common system Rail. Such nozzles have a more complex design. In particular, they include an intake and drain chokes, a solenoid valve and a control chamber. The injector works as follows.
The movement is based on the use of fuel pressure both during injection and when it is stopped. In the initial position, the solenoid valve is de-energized and, accordingly, closed. In this case, the nozzle needle is pressed against its seat under natural fuel pressure on the piston in the control chamber. That is, there is no fuel injection. Since the diameter of the needle is much smaller than the diameter of the piston, there is more pressure on it.
When a signal from the ECU is applied to the solenoid valve, it opens the drain throttle. Accordingly, fuel begins to flow into the drain line. However, the intake throttle prevents rapid pressure equalization between the control chamber and intake manifold. Accordingly, the pressure on the piston decreases slowly, but the pressure on the needle does not change. Therefore, the needle rises under the differential pressure and fuel injection occurs.
The third type is piezoelectric nozzles... They are considered the most advanced and are used on diesel engines equipped with a common rail fuel system. The design of such a nozzle includes a piezoelectric element, a pusher, a switching valve, and a needle.
The electrical resistance of piezoelectric injectors is several tens of kOhm.
At the moment when fuel does not flow through the nozzle, its needle sits tightly in its seat, since high fuel pressure presses on it. When a signal is received from the ECU to the piezoelectric element, which is an actuator, then at that moment it increases in size (length), and thus pushes the piston. As a result, the valve opens, and through it the fuel enters the drain line. The pressure at the top of the needle decreases and the needle rises. In this case, fuel is injected.
The main advantage of piezoelectric injectors is high speed their triggering(approximately 4 times faster than hydraulic). This makes it possible to carry out multiple fuel injection in one engine cycle. In the process of feeding, the amount of supplied fuel can be controlled in two ways - the time of exposure to the piezoelectric element, as well as the fuel pressure in the rail. However, piezoelectric injectors have one significant drawback - they are not repairable.
The operation of the electromagnetic injector of the injection engine
The operation of the injector in the Common Rail system
Since the working principle diesel injectors is somewhat more complicated than gasoline ones, it makes sense to consider in more detail the algorithm of their operation using the example of early releases of Common Rail injectors.
How does a diesel injector work
Based on the information received, the ECU controls various engine elements, including fuel injectors. In particular, for what period of time and when exactly they should be opened (the moment of opening).
The diesel injector operates in three phases:
- Pre-injection... It is necessary in order for the fuel-air mixture to have the desired quality and ratio. At this stage, a small amount of fuel is fed into the combustion chamber in order to increase the temperature and pressure in it. This is done to speed up the ignition of the fuel during the main injection.
- Main injection... Based high pressure obtained at the previous stage, a high-quality homogeneous combustible mixture is created. Its complete combustion ensures maximum power engine and reduces the emission of harmful gases.
- Additional injection... At this stage, cleaning takes place particulate filter... After the main injection, the pressure in the combustion chamber drops sharply, and the injector needle returns to its place. As a result, fuel ceases to flow into the combustion chamber.
- Cam camshaft moves the injector plunger, freeing its fuel channels.
- Fuel enters the injector.
- The valve closes, fuel stops flowing, and pressure starts to build up in the injector.
- When the boundary pressure is reached (for each model it is different, and amounts to several MPa), the nozzle needle rises, and a preliminary injection occurs (in some cases there may be two preliminary injections).
- The valve opens again and the pre-injection ends.
- Fuel enters the line, its pressure decreases.
- The valve closes, as a result of which the fuel pressure begins to rise again.
- When the operating pressure is reached (more than with the preliminary injection), the injector needle spring is released and the main fuel injection occurs. The greater the pressure in the nozzle, the more fuel will enter the combustion chamber, and, accordingly, will develop high power engine.
- The valve closes, the main injection phase ends, the pressure drops, the injector needle returns to its original position.
- Additional fuel injection occurs (usually there are two).
Any fuel injector is characterized by the following technical parameters:
- Performance... This is the most important parameter that characterizes the amount of fuel that the injector passes per unit of time. Usually measured in cubic centimeters of fuel per minute.
- Dynamic range of work... This indicator characterizes the minimum fuel injection time. That is, the time between the opening and closing of the fuel injector. Usually measured in milliseconds.
- Spray angle... Quality depends on it fuel mixture formed in the combustion chamber. Indicated in degrees.
- Spray Torch Range... This indicator determines in what fraction the atomized fuel particles will be located, and how they will be fed into the combustion chamber. Accordingly, this indicator is also critical for the formation of a high-quality fuel mixture. Measured as a conventional distance in millimeters or their derivatives.
Each injector manufacturer has its own designations for encrypting the technical data of its products. Therefore, when buying, ask the seller for the relevant information or on the Internet.
If at least one of the listed parameters goes beyond the permissible limits, the injector will work incorrectly and form a poor-quality fuel-air mixture. And this, in turn, will adversely affect the operation of your car's engine.
There is also a separate type of nozzles for injection engines with direct injection... Their main difference is their high response speed, as well as the increased voltage at which they operate. Let's consider them in more detail.
Direct injection engine injectors
FSI injector device
These injectors also have another name - GDI (FSI). It was invented in the bowels of Mitsubishi, when its engineers began to produce engines with direct injection of fuel, running on super-lean mixes... Their work is based on the precise timing of the actuation of raising and lowering the working needle.
So, in conventional injection engines, the opening time of the injector is about 2 ... 6 ms. And injectors in engines operating on super-lean mixtures - about 0.5 ms. Therefore, the usual supply of standard 12 V to the injector can no longer provide the required response speed. To accomplish this task, they work on Peak-n-Hold technologies, which means “peak voltage and retention”.
The essence of this method is as follows. The nozzle is supplied high voltage (for example, a voltage of about 100 V is supplied to the injectors of the said Mitsubishi company). As a result, the coil reaches saturation very quickly. At the same time, its winding does not burn out due to the existing back EMF. And to hold the core in the coil, a magnetic field with a lower value is needed. Accordingly, less current is needed.
Graph of current and voltage at the GDI injector
That is, the operating current in the coil first rises very quickly and then drops rapidly. At this point, the Hold phase begins. That is, the fuel injection time is from the start of the pulse to the second inductive burst. Such methods are used by automakers Mitsubishi and General Motors.
However, the manufacturers Mercedes and VW use the developments of the BOSCH company. According to their method, the system does not reduce the stress, but uses pulse width modulation(PWM). The task of implementing this algorithm is assigned to a special block - Driver Injector. As a rule, it is located near the nozzles (for example, Toyota and Mercedes locate the block in a horizontal position in the area of the shock absorber cup, which is the optimal solution today).
PWM on FSI injector
All FSI engines over 90 hp equipped with an improved fuel system. Its difference is:
- parts of the high-pressure pump and injector ramps have a special anti-corrosion coating that protects them from exposure to fuels with an ethanol content of up to 10%;
- high pressure pump control changed;
- the fuel drainage pipeline (to the tank), which leaked along the plunger, was eliminated as unnecessary;
- the fuel discharged through the safety valve installed on the injector rail is diverted through a relatively short pipeline into the circuit low pressure, in front of the high pressure pump.
As for the operation of GDI engines, it is worth noting that it is very sensitive to fuel quality, timely replacement fuel filter... Do not forget to clean the fuel system and change the oil in a timely manner.
Advantages and Disadvantages of Fuel Injectors
Undoubtedly, fuel injectors offer advantages over the traditional carburetor. In particular, they include:
- fuel savings made possible by precise metering;
- low emission exhaust gases into the atmosphere, high environmental friendliness (lambda is in the range of 0.98 ... 1.2);
- increase in motor power;
- ease of starting the engine in any weather;
- no need for manual adjustment of the injection system;
- wide possibilities for controlling the engine in different modes (that is, improving its dynamic and power characteristics);
- the composition of exhaust gases from injection engines meets modern requirements regarding this parameter and harmfulness to the environment.
However, nozzles have their drawbacks as well. Among them:
- high probability of their clogging when using low quality fuel;
- high cost compared to old carburetor systems;
- low maintainability of the nozzle and its individual units;
- the need for diagnostics and repairs using special expensive equipment;
- high dependence on the constant availability of power supply in the car network (in modern systems controlled by electronic devices).
However, despite the existing drawbacks, today injectors are used in most automobile gasoline and diesel engines as more technologically advanced and environmentally friendly fuel injection systems. Concerning diesel engines, then there the old mechanical injectors were replaced with newer ones with electronic control.
Location of nozzles
Depending on the type of nozzles and the injection method, the position of the nozzles may vary. In particular:
- If the car uses central fuel injection, then one or two nozzles are used for this, located inside the intake manifold, in the immediate vicinity of throttle... This system was used on older cars at a time when manufacturers began to abandon carburetor engines in favor of injection.
- With distributed injection fuel for each cylinder has its own injector. In this case, it can be seen at the base of the intake manifold.
- If the engine uses direct fuel injection, then nozzles are located in the upper area of the cylinder walls... In this case, they directly inject fuel into the combustion chamber.
Regardless of where the nozzle is installed, it becomes dirty during its operation. Therefore, it is necessary to periodically check their condition and. In the relevant articles on the site, you can find out in detail:, implement or.
In order to clean the nozzles, two methods are used - ultrasonic and chemical cleaning. Each of these methods can be used under different conditions. So, in the process of contamination of the fuel system and, in particular, the nozzles, hard and soft deposits are formed on the walls. At first, soft ones appear, which are easily washed off under the influence of chemicals. When soft deposits are compacted, they turn into hard ones and you can get rid of them only with the help of ultrasonic cleaning.
Ideally, dry cleaning of nozzles should be carried out approximately every 20 thousand kilometers. And ultrasonic no more than 1-2 times over the entire period of operation, since it destroys the insulation of the winding.
If the nozzle was used more than 100 thousand kilometers of run, then chemical cleaning is not only impractical for it, but also harmful... In its process, large particles of solid deposits can break off, and when they come out, they can simply clog the needle. This is especially true for injectors with direct fuel injection.
When using ultrasonic cleaning, it is important to know at what normal operating voltage the nozzle is operating. The fact is that the standard voltage of 12 V does not provide a high opening and closing speed of the injector. Therefore, nowadays, many car manufacturers use reduced voltage. For example, Toyota injectors operate at 5 V, and Citroen injectors at 3 V. Therefore, they cannot be supplied with the common 12 V voltage, as they will simply burn out. We will talk about the voltage across the injectors a little below.
The best cleaning will be consistent use of the ultrasonic and chemical cleaning method... So, at the first stage, hard deposits turn into soft ones, and at the second stage, they are removed with the help of chemicals.
There are also special additives to add to fuel tank ... Their function is to flush out the injectors when fuel with a cleaning agent passes through them.
Let us dwell in more detail on the question of what voltage is supplied to the engine injectors. First of all, you need to understand that they are controlled by electrical impulses. Moreover, “+” from the battery is fed directly to the injector through the fuse, but “-” controls the ECU. That is, in different moment time, the voltage at the injector is constant. However, if measured with oscilloscope(the multimeter in this case may not show anything, since the pulses are very short-lived), then this device will show the average value. It will depend on the frequency with which the pulses are sent to the injector.
Graphs of voltage impulses on injectors
The graphs shown in the figure will help us answer the question - what voltage is supplied to the injector. The longer the voltage pulses applied to the injector, the higher the average operating voltage.(the pulse duration for most machines is within 1 ... 15 ms). And long impulses are given at high operating engine speeds. Accordingly, the higher these same speeds, the higher the average operating voltage at the injectors will be. That is, working 12 V is supplied to the injectors (in fact, a little less due to a slight voltage drop across the control transistor), however, in a pulse.
Some car owners try to open the injector by simply applying current from the battery in order to clean it. It is necessary to understand that stress directly from the battery cannot be applied to the injector, since there is a risk that it will fail (its winding will burn out). A pulse is supplied to the device through a transistor switch. It acts for a short time, since the winding in the nozzle heats up quickly and can simply burn out. In the process of engine operation, the opening time is controlled by the ECU, and its natural cooling, albeit insignificant, is carried out by the incoming fuel.
As mentioned above, car manufacturers use injectors with different operating voltages. That's why ideal solution will look at this information in car manual or on the manufacturer's website. If you cannot find this information, then the selection of voltage for opening the injector must be approached carefully.
In practice, experienced motorists advise using a special stand to open the injector. However, you can get by with simpler devices. For example, buy a Chinese power supply with an output voltage adjustable within 3 ... 12 V (usually in 1.5 V steps). The connection diagram must necessarily have a button without a stable position (for example, from an apartment bell). To open the nozzle, you should first feed the most low voltage increasing it in case the injector did not open.
If you have low-resistance injectors, then you can open them literally for a split second. Nozzles with high resistance can be kept open longer - 2 ... 3 seconds.
You can also use rechargeable battery from a screwdriver. Having disassembled it, you will see the so-called "banks" - small batteries. Each of them produces a voltage of 1.2 V. By connecting them in series, you can achieve the required voltage to open the injector.
Injector control
As mentioned above, the injectors are controlled using electronic unit control (ECU) of the car. Based on information from numerous sensors, its processor makes decisions about which pulses to apply to the injector. The engine speed and its operating mode depend on this.
So, the input data for the controller are:
- position and speed crankshaft;
- mass quantity of air consumed by the engine;
- coolant temperature;
- throttle position;
- oxygen content in exhaust gases (in the presence of a feedback system);
- the presence of detonation in the engine;
- voltage in the electrical circuit of the car;
- machine speed;
- camshaft position;
- air conditioner operation;
- incoming air temperature;
- driving on uneven road (with a rough road sensor).
The program embedded in the ECU controller allows you to select the optimal engine operating mode in order to save fuel, select the nominal engine operating mode and ensure comfortable car operation.
Conclusion
Despite the simplicity of its device, fuel injectors, if improperly maintained, can bring a lot of trouble to the car owner. So, if they are clogged, the car will lose its dynamic characteristics, excessive fuel consumption will appear, and there will be a large amount of burning in the exhaust gases. Therefore, we recommend that you monitor the condition of the fuel injectors of your car engine, and periodically clean them. Remember that malfunctions with these essentially trivial and cheap parts can turn into problems with more expensive parts in your car.
The location of the electrical connector (1) supply voltage to the fuel
injector and connector (2) on the fuel injector
PERFORMANCE ORDER
1. Disconnect the electrical connector from the first cylinder fuel injector, see.
rice. The location of the electrical connector (1) supply voltage to the fuel
injector and connector (2) on the fuel injector.
2. Connect the control LED to the contacts of the connector (1) (see fig.
Location of the electrical connector (1) supplying voltage to the fuel injector and
connector (2) on the fuel injector). When cranking the engine crankshaft
starter, the LED should flash.
3. In the same way, check the voltage supply to the rest of the fuel
nozzles.
LED does not flash on any of the cylinders
The arrangement of the contacts on the electrical connector for supplying voltage to
fuel injector
PERFORMANCE ORDER
1. Connect the control LED to pin 1 of the electrical connector for
supply voltage to the fuel injector and vehicle earth, see fig. Location
contacts on the electrical connector for supplying voltage to the fuel injector.
2. Connect pin No. 2 of the electrical connector to vehicle ground.
3. Turn crankshaft engine starter. In this case, the LED should
blink. If not, check the entire fuel supply circuit.
nozzles.
LED does not flash on only one or several cylinders
PERFORMANCE ORDER
1. Check the condition of the electrical supply circuit of the fuel injectors and determine
and repair the point of open circuit or short to ground.
2. Check the operation of the engine control unit.
Resistance test
Ohmmeter connection points for testing fuel resistance
injectors
PERFORMANCE ORDER
Disconnect the electrical connectors from the fuel injectors in sequence and,
using an ohmmeter, check the resistance of the fuel injectors, which should
be in the range from 12 to 17 ohms, see fig. Ohmmeter connection points for
checking the resistance of the fuel injectors.
A warning
On an engine warmed up to normal working temperature, resistance
the fuel injectors are increased by 4-6 ohms.
If the resistance of the fuel injector is different from the required one, replace
fuel injector.
