It is possible to start a warm diesel engine without using a glow plug, or in warm climates, thanks to the relatively high temperature of the intake air and the relatively low ignition temperature of diesel. However, this isn’t enough to ensure proper ignition of the injected fuel in all temperatures, which results in increased exhaust emissions. A glow plug solves this issue. It is an electrical heating device located in each cylinder of the diesel engine that ensures reliable starts in all weather conditions.
How do glow plugs work?
Unlike a spark plug that is working continuously while you drive, glow plugs are only needed during the ignition process. The glow plugs work by electrifying the heating element so it heats up and emits visible light (hence the name). Intake air is compressed before the fuel injector spray directs fuel onto the hot tip of the glow plug during the injection of the fuel. The injected fuel mixes with the compressed air, evaporates and starts combustion almost simultaneously, even when the engine is cold.
Do the glow plugs stay on whilst the engine is running?
The post-heating time was introduced in more recent vehicles. This was necessary due to increasingly strict exhaust gas standards and the optimisation of combustion processes required as a result. The glow plugs remain switched on during the post-heating time even if the engine is running. The length of the post-heating time is determined by the type of engine and the engine temperature. Only special “post-heating” glow plugs are used for this function.
How long do glow plugs last?
Glow plugs can last up to 160 000 km. They are extremely long lasting. But at times a glow plug can fail and therefore will need to be replaced. If you find the vehicle difficult to start. Check the plugs.