When you start up a diesel-powered vehicle, the following actions happen:
- The glow plug control module determines the timing and electric current required by the glow plugs based on input from the Engine Control Unit;
- The heating element in the glow plug is electrified so it heats up and emits visible light (hence the name);
- Intake air is compressed;
- The fuel injector spray directs fuel onto the hot tip of the glow plug;
- The injected fuel mixes with the compressed air evaporate and starts combustion almost simultaneously, even when the engine is cold;
- The glow plug remains on during the pre-heating phase to ensure correct combustion of the fuel and reduce the environmental impact of your car.
This process is helped by the increase in temperature of the intake air during compression and the relatively low ignition temperature of diesel. However, a glow plug control module is still essential, as without it controlling your glow plugs, the compression temperature might not be high enough to ensure proper ignition of the injected fuel in a cold diesel engine. This would result in increased exhaust emissions.