Checking the pre-glow system

If you suspect a defect in the pre-glow system of a diesel engine, proceed as follows:

Check the fuses in the engine electrics.

Is the main fuse OK? (socket 1) onboard supply?

If there are no defects in it, then check the voltage on the glow plugs with a multimeter.

If there is a minimum of 11.5 V, do not miss the opportunity to check the glow plugs.

To do this, disconnect the wire on one of the four glow plugs.

Connect a test lamp between ground and the disconnected wire.

Disconnect the coolant temperature sensor connector and secure it in place.

Put the ignition key in position «Vorgluhen» - preheating.

If the control lamp now lights up for about 20 seconds, then the voltage at the glow plugs and the pre-glow time set by the control unit are in order.

If the test lamp does not illuminate, check the main fuse or pre-glow relay.

If the pre-glow time is not reached, then look for a defect in the control unit.

Faulty pre-glow system

You will probably only notice defects in the pre-glow system in severe frost (below -10°C). Only then will the diesel engine become reluctant to do its job without external heating energy. With a close inspection, you can recognize possible defects in advance: pay attention to the exhaust gases of your Focus. If blue plumes of smoke are coming out of the muffler, then read the fault memory in your workshop as a preventive measure - blue smoke is a signal of cold combustion. Small clouds should not bother you.