What are Glow Plugs and How Do They Work? | High-Quality Glow Plugs | DIY Car Service Parts | Middlewich


August, 2019

What Are Glow Plugs and How Do They Work?

Glow plugs are like mini heaters in your car’s bonnet. As heating elements, they warm the air and diesel in your engine for effective combustion.

Glow plugs share the same functionality as spark plugs. But rather than sparking the ignition in petrol engines, they heat air and fuel to start diesel engines.

Each diesel engine has a glow plug for every cylinder, which is why different makes and models need different numbers of plugs.

Glow Plug Anatomy | DIY Car Service Parts | Middlewich Spa

Glow Plug Anatomy

A glow plug begins as a heating coil, which is inserted into a metal tube. The tube is filled with electrically insulating ceramic powder and sealed at one end. When the glow plug is electrically energised, its heated tip can exceed 1000°C within a few seconds.

Ceramic glow plugs are an alternative to standard plugs. These include a heating element that is encased in ceramic (Silicon Nitride). The casing allows the glow plugs to heat particularly quickly, reaching higher operating temperatures for extended periods of time.

Note: good-condition, high-quality glow plugs heavily reduce exhaust gases emitted by your vehicle, keeping your environmental impact to a minimum.

How Do Glow Plugs Work? | High-Quality Glow Plugs | DIY Car Service Parts | Middlewich

How Do Glow Plugs Work?

Unlike spark plugs, glow plugs need to be warm enough under pressure to self combust. In hot weather, fuel needs little assistance from other car parts to achieve this. However, diesel engines often struggle to ignite fuel in cold weather. The glow plugs heat the fuel in order for the engine to start.

To start the engine, the intake air is compressed and, as the piston rises, the engine injects diesel into the combustion chamber. The injected fuel combines with the air, evaporates and ignites.

The ignition happens so quickly after evaporation that these processes are almost simultaneous.

Glow plugs undergo a three-phase process when the engine is started.

1) Pre-Heating

The glow plugs heat quickly to start the engine.

2) Temperature Maintenance

The glow plugs maintain their temperature to ensure optimal combustion.

3) Post-Heating

The glow plugs remain heated for a few minutes after the engine has been started to maintain the combustion process.

Read our blog post on how glow plugs are manufactured here.

Finding the Right Glow Plugs | DIY Car Service Parts | Middlewich

Finding the Right Glow Plugs

With thousands of glow plugs available to choose from, it can be an overwhelming task to find the replacements for your car.

But by entering your number plate into our car lookup tool, you can find the best glow plugs for your vehicle within seconds.

With one of the widest high-quality glow plug ranges on the market, DIY Car Service Parts stocks plugs from the top recommended manufacturers, providing glow plugs for every make and model.


All DIY car service parts are manufactured by trusted, high-quality brands. Here are just a few of the brands that we stock.

About DIY Car Service Parts

Whether you’re changing your own car parts or saving costs by providing them to your local garage, DIY Car Service Parts is the ultimate site for easily identifying the vehicle parts that you need.

DIY Car Service Parts isn’t just about accessing car parts from the best brands at the lowest prices. With over 35 years’ experience in the automotive industry, we are experts in the car parts field. Our specialist team is on hand to answer any of your queries and offer valuable advice so that you can understand more about the ways that your car works and get savvy under the bonnet.

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