Glow Plugs
During cold starts, glow plugs are used to preheat swirl chambers. When current is applied, glow plugs become red hot. A temperature sensor connected to a time circuit in glow plug relay controls pre-heating time.
To start a cold engine, pull out cold start knob to left of steering column (Volkswagen only). Turn ignition switch to glow plug position (No. 2). When light goes out, crank the engine. At below freezing temperatures, depress accelerator pedal while cranking. About 2 minutes after engine starts, push cold start knob in fully.
NOTE:
Cold starting device of Audi 4000 and 5000 is automatically controlled by engine coolant passing over a thermostat. When engine is cold, thermostat pulls on advance lever advancing injection timing.