Glow plugs - check
The fact that one of the glow plugs is defective is usually noticeable when starting a cold engine. For all cylinders with serviceable glow plugs, the mixture ignites immediately, and the cylinder with a faulty spark plug seems to lag behind and get out of the working rhythm. Exhaust gases are dark blue. It may also happen that during the warm season a defect in a candle or several candles does not manifest itself in any way, but this will become obvious when you first start a cold engine.
1. Check the 80 A fuse.
2. Open the fuse box cover (see illustration).
3. Check that the fuse link has not oxidized or burned out. Replace defective insert.
4. Check the voltage supply to the candles, if the fuse is OK.
5. Connect the tester with a control diode bulb to «mass» (-) and the place of attachment of the supply wire of the candle with red-white insulation (see illustration).
6. Disconnect the plug of the coolant temperature sensor.
7. Turn the ignition key to position «warm up». The diode lamp should light up, which confirms the power supply. If the lamp does not light up, then the fuse or power wire is faulty.
8. Check the candles themselves, if the voltage supply is normal.
9. Remove nozzles together with fuel lines.
10. Remove the injector heat shields. When installing, do not forget to replace the old heat-shielding gaskets with new ones. Do not disconnect the spark plug wire.
11. Turn the ignition key to position «warm up». If the engine is warm, disconnect the coolant temperature sensor connector.
12. Watch the glow plugs through the holes in the cylinder head. In this way, you can determine which of the candles is faulty or install a candle with a weak glow (see illustration).
13. Replace defective glow plug. It is recommended to replace all candles at once. To unscrew and install the candles, a key of 12 is required. The tightening torque of the candles is 30 Nm.
Glow plugs are rated for 15,000 engine starts. Practice shows that candle pins burn out even before this period. Typically, burnt out glow plug pins are the result of a defective fuel injector. In this case, the nozzles must be checked and, if necessary, replaced. An unadjusted start of injection pump supply also affects «survivability» glow plugs.
AUDI 80 vehicles with TD engine are fitted with the following glow plugs:
- Beru 857 MJ;
- Bosch, article no. 0250 201 031;
- Audi article no. 102 13002.
Glow plug relay - check
14. Disconnect the power wire with red and white insulation from the glow plug.
15. Connect a tester with a control light to this wire. Be careful not to short circuit.
16. Connect the second wire of a tester to weight.
17. Disconnect the plug of the coolant temperature sensor.
18. Turn the ignition key to position «warm up» and observe the tester indicator light. It should remain lit until the preheat indicator light on the instrument panel goes out. The warm-up time is approximately 8 seconds. Then the control lamp of the tester should light up again for about 10 seconds.
19. Turn the ignition key in the lock to position «Turned off», and then back to position «warm up». As soon as the indicator light on the instrument panel goes out, start the engine and let it idle. After starting the engine, the control lamp of the tester should be on for 180 seconds.
20. Perform a final check. Turn the ignition key in the lock to position «Turned off», and then back to position «warm up».
21. Connect an extension wire to the brown-grey wire at the terminal of the disconnected plug of the coolant temperature sensor and lead it to «mass» (-), for example, on the engine. The control lamp of the tester should go out immediately.
If the control lamp lights up as indicated above, then the glow plug relay is OK. Possible malfunctions of the relay may be caused by a malfunction of the coolant temperature sensor. If the tester's control lamp does not work as indicated above, then check the power wires using the circuit diagram. If they are normal, then the candle switch relay should be replaced (see illustration 13.0a).
Coolant temperature sensor - check
The coolant temperature sensor can be checked with an ohmmeter when removed.
22. Disconnect the temperature sensor plug (see illustration).
23. Connect an ohmmeter to the sensor. Connect one wire of the ohmmeter to the contact on which the brown-gray wire is connected, and the second to the wire with brown insulation.
24. Read the ohmmeter reading by testing the resistance of the sensor at two temperatures. At a temperature of approximately 20°C (room temperature) the ohmmeter should read about 1000 ohms, and at about 120°C the ohmmeter should read about 100 ohms.
If the ohmmeter does not respond to a change in temperature or the ohmmeter readings differ significantly from the rocked ones, then the sensor should be replaced.
Control lamp warming up on the instrument panel - check
If the engine has a sufficient temperature, then it is started without preliminary warming up and the control lamp on the instrument panel does not light up in such cases. When starting a cold engine, it should light up as soon as the ignition key is turned to the appropriate position. The control lamp can be checked without dismantling.
25. Disconnect the glow plug relay.
26. Connect relay terminal 49/L with auxiliary wire to «weight» (-).
27. Turn the key in the ignition switch to position «warm up». The control lamp should light up. Otherwise, either it burned out or its power wire is broken. If the control lamp lights up, and this did not happen before performing the test, then the glow plug relay may be faulty. Check the relay. If the indicator light on the instrument panel lights up for too long or, conversely, for too short a time, then the cause of this may be a defect in the coolant temperature sensor.
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