1. Make sure the spark plugs are producing spark.
2. Check that fuses 13, 21, 25, 27, 28 and 32 are good and provide power to the ignition and fuel injection systems.
3. Visually check the condition of wires, plugs, etc.
4. Check the ignition coil, Hall sensor or engine speed sensor or ignition timing sensor. If, after following these steps, the fault cannot be found, contact the workshop for a printout of the ignition system fault records.
Spark plug
5. Disconnect the high voltage wire from the spark plug.
6. Remove the spark plug.
7. Put the tip of the high voltage wire on the removed candle and attach it to the cylinder block, ensuring good contact with «weight». It is best to attach an auxiliary wire to the thread of the candle, which then bring it to the cylinder block.
8. Ask the assistant to turn the engine with a starter. If the spark plug produces a spark, then the power to the plugs is good. It is possible that the main adjustment of the ignition system is violated. If there is no spark, then do the same with the second candle. If this candle does not work, then it is necessary to check the entire system.
9. Make sure that the wires and plugs are connected correctly and that the contacts are not bent or oxidized.
10. Make sure that there are no cracks or sparks on the ignition coil housing. If the cover shows signs of damage, then remove the cover and check its inside.
11. Check high voltage wires. They are sensitive to flashover and leakage currents.
Make sure the parts of the power system are dry. Moisture on these parts favors spark flashover.
Attention! When performing measurements on the ignition system, do not forget that you can connect and disconnect measuring instruments only with the ignition off.
Along with the failure of the ignition system due to a lack of power, too little voltage in the network can also cause a failure. Use a voltmeter to check voltage. The main condition for such measurements is a normally charged battery and good fuses.
13. Inspect the fuses and make sure they are good.
14. Four- and five-cylinder engines. Disconnect the output stage connector.
15. Connect a voltmeter to pins 1 (terminal 15) and 3 («weight») plug.
16. Turn on the ignition. The voltmeter should show at least 11.5 V. If there is no voltage at all or it is less than specified, then there is a defect in the wire to the ignition switch.
17. Four-cylinder engine. Perform the same measurement on the power wire of the Motronic or Digifant fuel injection and ignition control unit. The wire has black and blue insulation.
18. Five-cylinder engine. Perform the same measurement on the power wire of the VEZ ignition control unit. The wire has black and blue insulation. In both cases, the voltmeter should show at least 11.5 V.
19. Six-cylinder engine. Disconnect the power supply plug to the ignition coils on the rear bulkhead of the engine compartment. The plug is painted white. Connect a voltmeter in turn to each of the three terminals at the top of the plug and to «mass».
20. Turn on the ignition. The voltmeter should show at least 11.5 V. If there is no voltage at all or it is less than specified, then there is a defect in the wire to the ignition switch.
21. Perform the same measurement on the power wire of the MPI/MPFI ignition and fuel injection control unit. The wire has a black-green insulation. And in this case, the voltmeter should show at least 11.5 V.
Causes of failure of the ignition system in such cases may be a malfunction of the ignition switch or a break in the power wire of the ignition switch / central wiring board and the central wiring board / ignition coils or the central wiring board / control unit. Check the connecting wires using the wiring diagrams.
Ignition coil
Four- and five-cylinder engines
A visual inspection of the condition of the ignition coil was performed earlier. To check the resistance of the ignition coil, disconnect all wires from the coil, turning off the ignition before that.
22. Perform the resistance of the primary and secondary windings of the coil, using a highly sensitive ohmmeter.
23. Connect an ohmmeter to the coil terminals 1/- and 15/+. Rated value of resistance: 0.5-1.5 ohm (see illustration).
24. Perform the next measurement by connecting an ohmmeter to terminals 1/- and 4. In this case, the ohmmeter should show 5-9 kΩ. If the specified coil resistance values are not achieved, the coil must be replaced.
When performing these measurements, it is impossible to determine the presence of a short circuit on the windings. If, despite good measurement results, there is still a suspicion that the coil is defective, then contact the appropriate workshop for a final check of the ignition coil.
Output stage
Four- and five-cylinder engines
The output stage cannot be tested in one go. It is checked in the following sequence:
25. Disconnect the output stage connector next to the ignition coil.
26. Connect a voltmeter to plug pins 2 and 3 («weight»),
27. Start the engine using the starter. The voltmeter should show at least 2 V.
28. Check up a food of system of ignition, as it was specified above.
29. Check ignition coil (see above).
If the system does not generate an ignition spark, despite the fact that all three of the above tests gave a positive result, then the output stage is faulty.
30. Replace the output stage and ignition coil.
High voltage transformer
Some AUDI 80 models with four-cylinder engines have a common ignition coil and output stage. This block is called a high voltage transformer. The connecting terminals 1 and 15 of the ignition coil in this case are closed with protective caps. Connection on «mass» passes through the body (see illustration 2.0).
31. Disconnect the three-pin plug and the main wire of the transformer, turning off the ignition before that.
32. Perform the resistance of the primary and secondary windings of the coil, using a highly sensitive ohmmeter.
33. Connect an ohmmeter to the coil terminals 1/- and 15/+. Rated value of resistance: 0.5-0.7 ohm.
34. Perform the next measurement by connecting an ohmmeter to terminals 15 and 4. In this case, the ohmmeter should show 3-4 kΩ. If the stated resistance values are not achieved, the transformer must be replaced.
When performing these measurements, it is impossible to determine the presence of a short circuit on the windings. If, despite good measurement results, there is still a suspicion that the coil is defective, then contact the appropriate workshop for a final check of the transformer.
To check the power, you need a voltmeter and auxiliary wires with tips.
35. Connect a voltmeter to both external contacts of the three-pin plug and turn on the ignition. The voltmeter should show a voltage of about 12 V. If the voltmeter does not register voltage, then you need to check the supply wire and the wire «masses». One of them is broken.
36. Turn off the ignition.
37. Perform a pulse test. Disconnect the plug of the injector or starting fuel valve, as well as the plug of the injector power wires.
38. Connect the tester with a control diode lamp to pins 2 and 3 of the transformer plug with auxiliary wires.
39. Ask the assistant to start the starter. The tester's LED should flash. If this does not happen, then the Hall sensor or the control unit for the fuel injection and ignition system is faulty.
40. Turn off the ignition.
Ignition coil
Six-cylinder engines
41. Disconnect all high voltage wires from the ignition coils.
42. Check the resistance of the secondary winding of the coil. To do this, connect a high-precision ohmmeter to cylinder connectors 1 and 6 (coil 1). The nominal resistance value is 9-14 kOhm.
43. In the same way, measure the resistance of the secondary windings of coils 2 and 3 by connecting an ohmmeter, respectively, to the connectors of cylinders 2 and 4, 3 and 5.
If the obtained data correspond to the nominal values, then check the resistance of the secondary winding of all coils.
44. Disconnect the white plug on the bulkhead of the engine compartment (ignition coil power plug).
45. Connect an ohmmeter to one of the three terminals 15 at the top of the plug.
46. Disconnect the three-pin plug of the output stage (also on the rear bulkhead of the engine compartment).
47. Connect alternately the second wire of the ohmmeter to all three terminals of the plug. The nominal value of all three measurements is 0.5-1.0 ohms. If the values obtained during the measurement do not correspond to the nominal values, then replace the ignition coil pack.
Output stage
Six-cylinder engines
48. Disconnect the power plugs of all six injectors.
49. Disconnect the four-pin plug of the output stage (on the bulkhead of the engine compartment). If a 3-pin plug is installed, the pin assignment is the same as for 4- and 5-cylinder engines (see illustration 2.23).
50. Connect the tester with a control diode bulb to «mass».
51. Connect the second wire of the tester alternately to pins 1, 3 and 4 of the plug (see illustration).
Ask an assistant to turn the engine with a starter at each measurement. The control diode lamp should flash during all three measurements. Otherwise, check the power supply or replace the output stage.
Hall sensor - check
Four- and five-cylinder engines
52. Disconnect the output stage plug.
53. Displace the rubber collar on the Hall sensor plug, thus providing access to the plug contacts from the back. Do not disconnect the Hall sensor plug itself. The plug is located on the side of the ignition distributor.
54. Connect a voltmeter to terminal 2 (purple insulated wire) and terminal 3 (purple-brown wire) connecting plug.
55. Turn on the ignition and crank the engine by hand to engage the ignition distributor.
The voltmeter should show a voltage of 0-0.5 V at the moment when the distributor diaphragm is outside the Hall sensor. With the diaphragm under the Hall sensor, the voltmeter should show at least 4 V.
If the voltmeter does not register any pulses, then check the power supply to the Hall sensor.
56. Disconnect the plug of the ignition distributor and connect the voltmeter to both external contacts of the plug.
57. Turn on the ignition. The voltmeter should show at least 9 V. If this is not the case, then the control unit is faulty or the power wire of the Hall sensor is broken.
Six-cylinder engines
58. Disconnect all injector plugs.
59. Displace the rubber cuff on the plug of the Hall sensor, thus providing access to the contacts of the plug from the back. Do not disconnect the Hall sensor plug itself.
60. Connect the tester with a control diode lamp to terminals 1 and 3 of the plug (plug terminals are marked) and check that power is supplied to the plug when the ignition is switched on. Otherwise, check the power wire.
61. Connect a tester with a control diode bulb to terminals 2 and 3.
62. Have an assistant turn the engine over with the starter. The LED light should flash. This means that the Hall sensor is normal.
Attention! If the Hall sensor is faulty, then the ignition distributor does not need to be changed. The Hall sensor is replaced separately.
Engine speed sensor
Six-cylinder engines
The engine speed sensor is located above the flywheel ring gear. The sensor power wire is routed to the rear partition of the engine compartment and fixed at the top of the partition. Therefore, it is not necessary to test the engine speed sensor from under the vehicle.
63. Check the power cable from the sensor to the holder on the rear bulkhead, as well as the plug connections.
64. Measure the sensor resistance with a precision ohmmeter. To do this, disconnect the three-pin plug and connect an ohmmeter to pins 1 and 2 of the sensor power supply (see illustration).
The ohmmeter should show 1 kOhm. Otherwise, the sensor is defective.
The third contact of the plug is connected to the shielding braid of the wire. To test the braided shield, connect an ohmmeter to pins 1 and 3, and then to pins 2 and 3. The ohmmeter should register infinite resistance. Otherwise, the engine speed sensor is defective.
Attention! The next check of the sensor is to remove it and clean its end. A dirty end face of the sensor or grease that has entered here will impair the functioning of the sensor.
Attention! Do not detach the sensor holder. Only the sensor itself needs to be removed for inspection and cleaning. If the sensor holder has been disconnected, it must be replaced by a workshop using special tools.
Ignition moment sensor - check
Six-cylinder engines
The ignition timing sensor is mounted directly on the cylinder block. Its verification is carried out through a connecting gray three-pin plug on the wire holder on the rear bulkhead of the engine compartment.
The procedure for checking the ignition timing sensor is identical to checking the engine speed sensor.
The control unit for the injection and ignition system in the usual sense of the word cannot be checked. A block failure can be established by interrogating the data drive about the failures that have occurred, contacting the workshop to print out such information.
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