Pre-heating system (diesel engines) (Peugeot 406)

Table of contents: Examination 🠇 Tightening torques, Nm 🠇

Each swirl chamber contains a glow plug. The glow plugs are used when starting a cold engine. The voltage supply to the glow plugs is controlled by a time relay in conjunction with the diesel injection electronic control unit (ECU).

On some models, the glow plugs remain on for a period after the engine has started, i.e. after the starter is turned off, the glow plugs continue to operate for another 3 minutes. The glow plugs cannot be interrupted during the first 15 seconds, but they can be switched off later if:

pressing the accelerator pedal more than 11 mm and holding it for more than 2.5 seconds;
coolant temperature over 60°C.

The indicator lamp in the instrument cluster lights when the glow plugs are operating. After the lamp goes out, the engine can be started. Voltage is supplied to the glow plugs for several seconds after the indicator lamp goes out. If no attempt is made to start the engine after the lamp goes out, the timer disconnects voltage from the glow plugs to prevent the battery from discharging and the glow plugs from overheating.

Examination

1. Connect a voltmeter between the glow plug supply line and ground. Turn on the ignition and check that voltage is supplied to the glow plugs at the appropriate time interval.

2. At an air temperature of 20°C, the time intervals for supplying voltage to the glow plugs should be 5–6 seconds, during which the indicator lamp lights, and 10 seconds after the indicator lamp goes out. The time the indicator lamp burns increases at lower temperatures and decreases as the temperature rises.

3. If voltage is supplied to the glow plugs, then the relay and wiring are good.

4. To locate a faulty glow plug, remove the air intake duct system and disconnect the crankcase ventilation hose from the oil filler neck. Disconnect the main supply wire and connecting bus from the glow plugs.

5. Using a tester (ohmmeter), check the integrity of the glow plugs by checking the resistance between the contact at the top of the plug and the body of the plug. The resistance of the glow plug is less than 1 ohm; if the tester shows high resistance, the glow plug is faulty.