A diesel car doesn’t use spark plugs. Instead, compression heat is used and this causes ignition in the engine. However, a diesel engine isn’t completely free of plugs. It will still use components which are known as glow plugs.
What a Glow Plug Does
You’ll find that there is a glow plug for each cylinder in your diesel car. It’s a piece of metal with a shape a little similar to a pencil. There’s a heating element on the tip. When you turn the key in an older diesel engine, you shouldn’t turn it all the way. Instead, partially turn until the wait to start light on the dash goes off. This indicates the heating element has reached a temperature at which it can start the engine.
How Often to Replace
There’s no set rule as when to replace glow plugs in a diesel car. A good indicator that you need new glow plugs is that it’s difficult to start the car, taking a few attempts. That will be especially true when the engine is cold. If you remove the glow plugs and look at them, you should replace if the glow plugs are blackened at all, or deformed in any way.