Description
1. The engine's swirl chambers are heated just before the engine is started by electric plugs, commonly called glow plugs. When the ignition key is turned to the "ON" position, a warning light comes on to let the driver know that the heating process is underway. When the light goes out, the engine is ready to start.
2. Current is supplied to the glow plugs via a relay installed either on the bulkhead of the engine compartment or on/near the upper mount of the suspension strut (depending on the model). Checking the serviceability
Note: The following information applies only to 11-volt glow plugs, please ensure that your vehicle has these plugs. Checking 5-volt glow plugs requires special equipment - please contact a specialist.
3. If the system is suspected of being faulty, check that battery voltage is supplied to the glow plug bus for a few seconds when the ignition switch is turned to the "ON" position. If this is not the case, the wiring or relay is damaged. The relay can be tested by replacing it with a known good component.
4. If voltage is supplied to the bus, but it is suspected that one or more glow plugs are not working, a large-range ammeter (0-50 A) can be used to identify the faulty plug. An ohmmeter is unlikely to be able to distinguish a good plug (resistance less than 1 ohm) from faulty.
5. Connect the ammeter between the bus and the feed wire. Have an assistant turn the ignition key. The current flowing through the grounded spark plug in the first few seconds of the test is 8-9 A. So, if the ammeter reading is much higher or lower than 32-36 A, one or more spark plugs are faulty. Disconnect each spark plug one by one to isolate the faulty one.
6. Alternatively, you can use a 12V bulb. Remove the busbar and connect the bulb between the positive battery terminal and each glow plug in turn. If the bulb lights, either the glow plug is good or there is a short circuit. If the bulb does not light, the glow plug is bad.
7. In addition to the above tests, a visual inspection of the suspected faulty glow plug can be performed. Proceed as follows:
8. There are glow plug testers available that consist of a housing that holds the plug, an ammeter, 12-volt connecting wires, and a simple timer that turns on LEDs at 5-second intervals. Without removing the glow plug, connect it with wires to a 12-volt battery and determine the time it takes for the tip of the plug to glow, after which the current drops.
9. You can make a similar device yourself.
10. Connect a wire to each terminal of an ammeter with a range of at least 30 A. For safety, connect one of the wires through a 30 A fuse.
11. Remove the suspected faulty glow plug from the cylinder head, clamp it with special pliers in a metal case and apply it to any point on the engine that is shorted to ground. Connect the wire coming from the positive terminal of the ammeter to the terminal of the glow plug. Ask an assistant to time it while you watch the tip of the glow plug.
12. Connect the wire from the negative terminal of the ammeter to the positive terminal of the battery and begin counting. Watch the ammeter needle and the tip of the glow plug carefully. The tip of the glow plug should glow red in about 5 seconds. After about 15 seconds, the current should drop from 25 amps to 12 amps.
13. Please note that the above figures are approximate. If the current during testing is close enough, the spark plug is probably OK.
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