Design Description
1. Each swirl chamber contains a glow plug (sometimes called a glow plug), screwed into the cylinder head. Glow plugs are energized before starting and during a cold engine start.
2. The electrical power supply to the glow plugs is controlled by the preheating control unit. Excluding later 1.9L engines (WJY) and all 2.0 liter engines, the control unit uses signals received from the coolant temperature sender and the accelerator switch on the high pressure fuel pump. On later 1.9L engines (WJY) and all 2.0 liter engines, the control unit is controlled by the electronic control unit for the injection system (see chapter 4B).
3. On some models, glow plugs are also used to «post-heating». With this function, the glow plugs remain on for some time after the engine is started. After the starter is turned off, the glow plugs begin to work in the mode «post-heating», which has a given duration. Post-heating only takes place when the engine is cold (coolant temperature below 60°C on 1.8 and 1.9 l engines and below 20°C on 2.0 l engines), and if a load is placed on the engine, the power supply to the glow plugs will be interrupted.
4. The driver is informed about the operation of the heating phase by a control lamp located on the front panel. The lamp goes out when the operation of the heating function already allows the engine to be started. Power continues to flow to the glow plugs for a few seconds after the lamp goes out. If no attempt is made to start the engine, the timer cuts off the electrical power to the glow plugs. This prevents the battery from draining and burning out the glow plugs.
Examination
Engines 1.8 l and 1.9 l
5. If the system is faulty, testing is typically done by substituting known-good items, but certain preliminary checks can be performed as described below.
6. If applicable, release the tabs on the right side and top of the engine cover, and then carefully remove the cover so as not to lose the rubber mounts.
7. Connect a voltmeter or 12V test lamp between the glow plug power wire and the «masses» (metal element of the engine or body). Check for a short circuit between the power circuit and the engine/body.
8. Have an assistant turn on the ignition and check the voltage applied to the glow plugs. Make a note of the time that the control lamp is on and the total time that power is applied before the system is turned off. Switch off the ignition.
9. At a coolant temperature of 20°C, the standard warning light duration should be 5 or 6 seconds. After the lamp goes out, another 10 seconds of power supply follow. The duration of the warning light increases at lower temperatures and decreases at higher temperatures..
10. If the power is not supplied at all, then the control unit or the corresponding electrical wiring is faulty.
11. To find a faulty glow plug, on models with a 1.9L D9B engine, remove the air distribution housing. If necessary, also remove the air intake duct and disconnect the vent hose from the oil filler pipe. For more information, please refer to chapter 4B. Disconnect the main power wire and connecting wire or bar from the top sections of the glow plugs. Be careful not to drop nuts and washers.
12. To check the continuity of the electrical circuit between each glow plug terminal and ground, use a continuity tester or a 12V test lamp connected to the positive battery terminal. Good glow plug resistance is very low (less than 1 ohm). Therefore, if the test lamp is not lit or the continuity tester shows high resistance, the glow plug is faulty.
13. If you have an ammeter, you can check the current in each glow plug. After an initial surge of 15 to 20 amps, each spark plug should be at 12 amps. Any spark plug that has more or less current than this value is probably bad.
14. As a final check, the glow plugs can be removed and inspected as described in the next paragraph.
Engines 2.0 l
15. The system can be tested as described in p.p. 7-14. However, verification will be difficult due to the temperatures at which the preheating system operates; at coolant temperatures above 0°C, no preheating is actually required. Approximate heating times are as follows:
Coolant temperature/Preheat duration
- -30°C / 20 seconds
- -10°C / 5 seconds
- 0°C / 0.5 seconds
- 18°C / No heating required