Genuine BOSCH glow plug
Part number 0250403021

A glow plug is a heating device that is used to start diesel engines. It is installed in the combustion chamber and operates by heating the air within the cylindrical chamber to ignite the fuel mixture. A diesel engine compresses the air in the combustion chamber to raise its temperature, and when fuel is injected into the chamber, ignition happens. However, this process requires the air to be at a certain temperature for the ignition to occur. When the engine is cold, the air in the combustion chamber is also cold, which means that the engine doesn't start. This is where a glow plug comes in handy.

A glow plug is heated electrically and is timed to heat up before the engine is ignited. The heating process takes a few seconds, and once the glow plug reaches the right temperature, it heats the air in the combustion chamber to the temperature required for ignition. This, in turn, leads to the ignition of the fuel and ultimately starts the diesel engine. Glow plugs are present in all modern diesel engines, and some systems have more than one glow plug for better reliability and faster heating. To sum up, a glow plug is a crucial component in diesel engines, which makes it possible for them to start even in cold temperatures.