Checking the diesel engine preheating system (VW Golf 4)

Location of diesel engine controls in the engine compartment of a vehicle with a TDI diesel engine

• 1 - exhaust gas recirculation valve;
• 2 - intake manifold changeover valve;
• 3 - fuel injector with needle movement sensor;
• 4 - control unit. For diesel engine with direct injection system. Height sensor integrated in the control unit;
• 5 - control valve for exhaust gas recirculation;
• 6 - magnetic valve. To limit the boost pressure;
• 7 - air flow meter;
• 8 - coolant temperature sensor;
• 9 - engine speed sensor;
• 10 - Electrical connector for needle movement sensor;
• 11 - Electrical connector for engine speed sensor;
• 12 - Electrical connector of the high-pressure fuel pump (HPFP). For the fuel temperature sensor, volume regulator and needle movement control sensor;
• 13 - injection start valve;
• 14 - fuel shut-off valve;
• 15 - high pressure fuel pump volume measurement post. With fuel temperature sensor, volume regulator and needle movement control sensor;
• 16 - absolute pressure sensor in the intake manifold with temperature sensor

The following items are not shown in the figure:

• A - brake pedal switch;
• B - brake light switch;
• C - accelerator pedal position sensor;
• D - clutch pedal switch.

Verification conditions

The voltage of the vehicle's on-board network must be no lower than 11.5 V.

The engine control device must be in normal condition.

The fuses in the glow plug supply circuit must be in good condition.

Examination

1. Turn off the ignition.



2. Disconnect the electrical connector from the coolant temperature sensor (A – coolant temperature sensor, 1, 3 – electrical connector contacts).

3. In this state, the engine management system considers the engine to be cold and will preheat the diesel engine when the ignition is turned on.

4. Disconnect the electrical connectors from the glow plugs.

5. Connect a voltmeter between one of the glow plug connectors and the vehicle ground.

6. Turn on the ignition. The voltmeter should show that voltage is supplied to the glow plugs for 20 seconds.

7. Otherwise, check the glow plug power supply circuit, find and fix the fault.