Glow Plugs

A glow plug is not applicable in all cars, in fact, if you drive a petrol car, you may have never come across a glow plug. Glow plugs are only used in diesel vehicles, however, they are similar to spark plugs. Instead of creating a spark for the ignition, they are responsible for heating the air within the engine to assist with the ignition process.

Different to petrol engines as they require a spark to ignite the fuel. Whereas a diesel engine will auto-ignite due to temperatures created by vastly higher cylinder pressures compared to that of a petrol engine. When an engine is being started up for the first time or during the colder months of the year, it can take longer for the cylinder to get the required temperatures to therefore ignite the fuel. This is where the glow plug comes into tuition in that it pre-heats the cylinder to allow combustion to happen straight away. Diesel cars are sensitive, therefore, in order for the car to start, the heating element has to take place for the combustion process to occur.

If your glow plugs are on their way out or no longer work, it can result in a number of issues. If you notice any of the below symptoms, you can check the health of your glow plugs by using a multimeter and testing the resistance.

• White Smoke - white smoke will occur when there is insufficient heat within the engine to burn the diesel fuel. This will occur when you start up your vehicle, you may notice a big puff of white smoke coming out of the exhaust. This is an indication that one or more of your glow plugs are not functioning correctly. Other issues within your engine can cause white smoke, however, if you test the glow plugs using a multimeter, you will soon find out if it is the glow plugs or something else causing the issue.
• Hard to start your engine - in the cold weather, if you are struggling to get your car started, this is an indication that the glow plugs are not working correctly, which means the combustion chamber cannot reach the right temperatures to start the engine.
• Check engine light - the check engine light will appear on the dash of your car. If you notice this, this is an indication that something is not working or functioning properly within your engine. If you notice this check engine light, as well as some of the other symptoms, this could mean your glow-ups need changing. However, a check engine light can also appear if there are other issues within your engine.
• Vehicle's fuel efficiency - another issue that can be caused by a bad glow plug is your fuel efficiency will not be as effective.

Your vehicle will start without a glow plug, however, this will depend on the current temperature. As mentioned above, your diesel glow plug is designed to assist in starting up your vehicle, if it is particularly cold, your vehicle may not start without them. If you notice any of the below symptoms, it is best to get a replacement plug to ensure your diesel car starts every time.