1. Make sure the ignition is OK.
2. Check the fuel system.
3. Check up visually a condition of components of system of injection of fuel.
If the cause of the malfunction after performing the above steps has not been established, then read the list of possible malfunctions of the fuel injection system and how to eliminate them, and also contact the workshop to print out the trouble codes registered by the control unit. Based on the information obtained, determine the cause and check the relevant part.
Attention! In the event of a sudden complete failure of the fuel injection system, first check the fuses No. 13, 21, 25, 27 and 28. Through them, the Mono-Motronic system is powered.
A leak in the intake manifold leads to the entry into the system of «side» air. The amount of this air is not included in the parameters stored in the memory of the electronic control unit and leads to a malfunction of the system. Excess air leads to an uncontrolled lean air-fuel mixture. This defect is especially noticeable when the engine is idling due to fluctuations in the number of revolutions. At full load on the engine, high-pitched detonation knocks appear in such cases.
4. Check the condition of the vacuum hoses and their fastenings. It is necessary to check all hoses on the injection system and intake manifold (vacuum brake booster hose, hot air supply hose, evaporative emission system hoses).
5. Warm up the engine and leave it to idle. Open the hood at the same time.
6. Spray from an aerosol can with the so-called starting fluid (For example, «Startpilot») the injection unit in the area of the flange on the intake manifold side, the gaskets of the intake manifold pipes, and the hoses of the units generating reduced pressure. Disconnect the plug of the lambda probe. If, when applying the specified liquid to a certain part, the engine speed increases, then this is the place of air leakage.
7. Make sure the fuel hoses are tight.
8. Check that the connection plugs fit properly and that the pins are not broken or bent. If necessary, spray the contacts with an aerosol to improve contact conductivity. Do not bend the contacts yourself.
Injection system components - check
Throttle Angle Adjuster
7. Disconnect the plug of the throttle valve angle adjuster.
8. Apply a maximum voltage of 6 V to the connector pins of the regulator plug. Positive charge lead (+) must be connected from above. For a four-pole plug, these are pins 1 and 2 (both upper), and for the six-pole - 1 and 6 (up and down). The pusher must fully move back.
9. Reverse the power supply. Now there should be a negative charge wire on top (-). The pusher must come fully forward.
If the regulator tappet is functioning when this test is performed in this manner, then the regulator is good. Otherwise, replace the regulator.
Additionally, you can check the resistance of the winding of the actuator motor of the regulator. On the mentioned contacts, the resistance should be 3-200 P.
idle sensor
10. Disconnect the plug of the throttle valve angle adjuster.
11. Connect an ohmmeter to contacts of the gauge of idling. On a four-pole plug, these are pins 3 and 4 (both lower), and for the six-pole - 4 and 5 (counting from top to bottom).
Attention! If the throttle valve control is replaced, the idle speed sensor must be adjusted. The work is done in the workshop.
Throttle angle potentiometer
12. Disconnect the throttle angle potentiometer plug.
13. Connect an ohmmeter to the pairs of contacts as indicated in the table. If the data obtained during the measurement do not correspond to those given in the table, then the potentiometer is defective and must be replaced. Given that the potentiometer is non-separable, for this it is necessary to replace the entire lower part of the injection system unit (see illustration).
Nozzle
Checking with the engine running. The engine must have an engine oil temperature of at least 60°C, which corresponds to a 10-minute drive immediately after starting a cold engine.
14. Remove the air inlet pipe.
15. Start the engine and leave it to idle.
16. Pay attention to the shape of the jet of fuel from the nozzle. It should be the same along its entire length and should exit in the direction of the throttle valve.
17. Shut off the engine to check the tightness of the injector closure. With the engine off, no more than two drops of fuel per minute should come out of the nozzle.
The following actions are carried out if the engine does not start.
18. Check fuses 13 and 27.
19. Remove the air filter or air inlet.
20. Have an assistant turn the engine over with the starter.
21. Monitor the injector and make sure it is supplying fuel to the system. If this does not happen, then disconnect the brown plug located on top of the injection system housing (see illustration).
22. Connect an ohmmeter to both middle contacts of the part of the plug that remained on the system case. At an air temperature of +15 - +30°C, the nozzle resistance should be 1.2-1.6 Sigma. Otherwise, the injector is faulty.
23. Turn out the screw with an internal polyhedron and replace the nozzle.
24. Check the power to the injector, if the resistance of the injector is normal.
25. Connect a voltage tester with a diode lamp (do not connect other devices) to both middle contacts of the disconnected part of the plug.
26. Start the engine. The LED light should be on. Otherwise, there is a break in the power wire or a defect in the control unit.
Forced idle mode
27. Remove the air filter or disconnect a branch pipe of an inlet of air.
28. Start the engine and raise the speed to 3000 rpm, and then at this speed remove the gas (close the throttle).
29. At the same time, monitor the operation of the nozzle. At the moment of closing the throttle valve, the jet of injected fuel must be interrupted for some time. This means that the forced idle mode is normal. If this is not the case, then check the throttle angle control and the electronic control unit (In workshop).
Coolant and intake air temperature sensors
30. Intake air temperature sensor. Disconnect the brown plug on the fuel injection housing.
31. Connect an ohmmeter to both external contacts of the sensor.
32. Coolant temperature sensor. Disconnect the plug of the blue two-pole sensor in the coolant pipe (see illustration).
33. Connect an ohmmeter to the sensor contacts.
34. Both sensors. Read the ohmmeter reading.
35. Verify, using the chart below, that the resistance values of both sensors and the air and coolant temperatures are currently within the curves in the chart. If not, then the sensor (And) replace (see illustration).
Fuel pressure
Accurate information about fuel pressure can only be obtained in a workshop when checked with an appropriate measuring device. On the assumption that the fuel pressure is not correct, disassemble the pressure reducing valve in the fuel injection unit. To do this, remove the four hexagon socket screws.
36. Check that the diaphragm is not damaged and that the valve itself is not clogged.
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