1. Make sure the ignition system is OK if your car's engine refuses to run.
2. Check the power supply 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 fuses Nos. 13, 21, 25, 27 and 28.
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 its supply leads to malfunctions in 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.
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 (brake booster vacuum hose, heated 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
A pressure gauge is required to check the pressure reducing valve and measure the fuel pressure (V.A.G 1318) with stopcock and adapter. The fuel pressure at idle should be within 2.5 bar, and when the vacuum hose is disconnected from the pressure reducing valve, the fuel pressure should increase to almost 3 bar (see illustration 8.0).
Throttle angle potentiometer
9. Disconnect the potentiometer plug.
10. Connect an ohmmeter to pins 1 and 2.
12. Open and close the throttle and at the same time monitor the ohmmeter. The resistance value should change evenly. To test the injectors, you need a voltage tester with an LED light.
13. Check the power to the injectors. To do this, disconnect the plugs of each injector in order and connect the tester to the contacts of the plug (see illustration).
14. Ask the assistant to start the engine. The diode lamp on the tester should be lit. Otherwise, the power wire is broken or the electronic control unit for the Digifant injection system itself is faulty.
15. Disconnect all injector power plugs to check the injectors themselves.
16. Connect an ohmmeter to both contacts of the first nozzle. The nominal resistance value is 15-20 ohms.
17. Perform the same test on the next injector.
18. Perform a leak test of the nozzle and the shape of the jet of injected fuel. To do this, remove the nozzles together with the fuel distributor. Do not disconnect power plugs and fuel lines.
19. Disconnect the start fuel valve plug and the coolant temperature sensor plug located on the left side of the exhaust pipe.
20. Dip nozzles into measuring cups.
21. Have an assistant operate the starter for a few seconds. The shape of the fuel jet for all four nozzles must be the same.
22. Disconnect the common power supply plug for the injectors located on the wiring harness.
23. Turn off the ignition, and then turn it on for about 5 seconds. No more than two drops of fuel should flow out of each nozzle. This is normal.
24. Disconnect the multi-pin connector of the intake air temperature sensor on the air volume flow meter (see illustration).
25. Connect an ohmmeter to both outer contacts of the sensor.
26. Disconnect the blue plug of the coolant temperature sensor in the coolant pipe (see illustration).
27. Connect an ohmmeter to the sensor contacts.
28. Both sensors. Read the ohmmeter reading.
29. Verify using the chart below that the resistance values of both sensors and the air and coolant temperatures are currently within the curves on the right side of the chart. If not, then the sensor (And) replace (see illustration).
30. Disconnect all injector plugs to check power supply and fuel start valve operation (see illustration).
31. Disconnect the start fuel valve power plug.
32. Connect a voltage tester with a diode lamp to the valve power plug using the auxiliary wires.
33. Disconnect the plug of the coolant temperature sensor.
34. Ask the assistant to turn the engine with a starter. The tester's diode lamp should light up for about 1-4 seconds. If the light does not light up, then the electronic control unit of the Digifant system may be broken.
35. Turn out the starting fuel valve. In this case, the valve power plug must be connected, and the injector power plugs must be disconnected. Do not disconnect the fuel line from the starting valve either.
36. Disconnect the coolant temperature sensor plug, if connected.
37. Lower the starting fuel valve into a container.
38. Have an assistant turn the engine over with the starter. The valve should open and supply fuel within 14 seconds. The shape of the fuel jet must be uniform along its entire length.
39. Wipe the valve dry before checking for leaks. Within a minute, no gasoline should come out of the valve and, in addition, the valve nozzle should not be wet. To check the lambda probe, a gas analyzer is required or this check must be carried out in a workshop. The conditions for the correct execution of the test and obtaining accurate data is the tightness of the exhaust system, as well as the availability of power to the lambda probe. Make sure the appropriate fuses are good.
40. Warm up the engine.
41. Connect the gas analyzer.
42. Start the engine and let it idle for at least two minutes.
43. Raise the engine speed to 2000 rpm.
44. Write down the readings regarding the content of CO.
45. Disconnect the reduced pressure supply hose from the throttle valve. Lock the hole in the pipe with your finger. The CO content should rise for a moment and then drop back down to the level that was recorded. If the CO content does not change, disconnect the power plug of the lambda probe (see illustration).
46. Pull the wires from both poles of the battery and alternately connect them to the plug contact. If at the same time the CO content changes, then the lambda probe is faulty. If, in this case, the CO content remains unchanged, then you need to check the power supply wires to the electronic system control unit. If everything is normal here, then the control unit is faulty.
47. Disconnect the plug of the power wire of the intake air flow meter. Contacts are numbered from right to left from 1 to 4.
48. Check the intake air temperature sensor on pins 1 and 4 as indicated in p. 2429 of this chapter.
49. Connect an ohmmeter to pins 2 and 3 to test the potentiometer.
50. Displace the valve shutter, following the readings of the ohmmeter. The resistance must change (see illustration).
51. Connect an ohmmeter to pins 3 and 4. The ohmmeter should show resistance between 0.5 and 1 kOhm. If the specified values are not achieved, the flowmeter must be replaced.
52. Turn off the ignition before starting to check the idle speed stabilization valve. In this case, a hiss will be heard from the valve. In addition, you can check if it vibrates while doing this. If not, then check the fuses.
53. Disconnect the idle speed stabilization valve plug if the fuses are OK (see illustration).
54. Check, by connecting a tester with a diode bulb, whether voltage is supplied to the contact of the wire with black and blue insulation (ignition on). Close the second contact of the tester to ground. If there is voltage, it means that the valve is receiving power. Now you need to check the valve itself.
55. Connect an ohmmeter and check up resistance on contacts of the valve. If the contact is good, then the ohmmeter reading should be in the range of 2-10 ohms. If the obtained values differ from the nominal values, then the valve must be replaced. If the resistance values \u200b\u200bare normal, then the defect may be caused by a wire break or the Digifant system control unit is faulty. To check the block in workshops, they use the VAG 1551 reading device. It makes no sense to measure using other devices.
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