Checking the diesel engine preheating system

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

• 1 - valve for exhaust gas recirculation;
• 2 - intake manifold switching valve;
• 3 - fuel injector with needle movement sensor;
• 4 - control unit. For diesel engine with direct injection system. The height sensor is integrated in the control unit;
• 5 - control valve for exhaust gas recirculation;
• 6 - magnetic valve. To limit boost pressure;
• 7 - air flow meter;
• 8 - coolant temperature sensor;
• 9 - engine speed sensor;
• 10 - electrical connector for the needle movement sensor;
• 11 - electrical connector for the engine speed sensor;
• 12 - electrical connector high pressure fuel pump (injection pump). For fuel temperature sensor, volume regulator and needle movement control sensor;
• 13 - valve for starting injection;
• 14 - shut-off fuel valve;
• 15 - post for measuring the volume of the high pressure fuel pump. With fuel temperature sensor volume regulator and needle movement control sensor;
• 16 - absolute pressure sensor in the intake manifold with a 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 car's on-board network must be at least 11.5 V.

The engine control device must be in good condition.

The fuses in the voltage supply circuit to the glow plugs must be good.

Examination

1. Switch off the ignition.



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

3. In this state, the engine management system assumes that the engine is 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 vehicle ground.

6. Turn on the ignition. In this case, the voltmeter should show that voltage is applied to the glow plugs for 20 seconds.

7. Otherwise, check the glow plug circuit, find and repair the problem.