MOTORPOS: The important role of glow plugs in a diesel engine
Although glow plugs can easily last more than 100 000 km they could stop working at any time.
A diesel engine is a powerful and complex piece of engineering.
Unlike a petrol engine that requires a spark, a diesel engine relies on pressure to compress the air within the cylinder. This compression increases the temperature of the air inside the cylinder to a level that will allow the spontaneous combustion of the diesel droplets that are injected into the cylinder. This is why diesel engines have such high compression ratios. Diesel needs at least 210°C to combust on its own.
When cold starting a diesel engine the low air temperature, as well as the cold piston and cylinder surfaces, make it difficult for high enough combustion temperatures to be reached. It is the role of glow plugs to heat the cylinders sufficiently to start the engine.
When glow plugs detoriate, a diesel will be slow to start and once it fires up will run roughly, miss and produce lots of white smoke.
Although glow plugs can easily last more than 100 000 km they could stop working at any time and need to be replaced when the above symptoms are present.
It is imperative that top quality glow plugs are used as inferior plugs may swell and be very hard to remove. The tips of poor quality glow plugs may also break off and end up in the cylinders.
