What Are The Differences Between Glow Plugs And Spark Plugs?

Most car engines need three things to work: fuel, air, and heat or ignition source. And glow plugs and spark plugs both serve as the main ignition sources in a combustion engine.

However, they differ in the engine where they are found. Spark plugs are seen in gasoline engines, while glow plugs work with diesel ones. 

Learn more about how spark plugs and glow plugs work in this article.

Explaining Glow Plugs And Spark Plugs

The Diesel World video first explained how engines work to understand the use of plugs better.

It stated that in middle school subjects, you are taught in science how compressing the air makes its temperature high. So the more compressed the air, the hotter. 

One of the key factors for an engine to work is heat or ignition. And sometimes, manual compression is not enough to produce the needed temperature, so plugs come in.

Either spark plugs or glow plugs, assist in producing the needed internal temperature for an engine to work.

On the other hand, not all diesel engines use glow plugs. Instead, some have a mesh wire-like grid heater that works the same as glow plugs. But for those that use glow plugs, one of its main roles is the cold starting. 

The compressor ratio is higher in a diesel engine than in a gas engine so that there’s guaranteed heat, so glow plugs aid in maintaining enough temperature for the engine.

The narrator in the Diesel World video clarified that a glow plug only helps in starting, not in the running. Once the engine starts to run, the glow plugs will stop working. 

Meanwhile, a gas engine needs spark plugs every time, as it’s used to ignite the gasoline air mixture.

How? The spark plugs receive the charge from an ignition coil to spark and ignite fuel. Also, they continuously work to ensure your gas engine runs smoothly.

Frequently Asked Questions

What do spark plugs look like? 

A standard spark plug has a conductor in the middle. It is surrounded by a ceramic insulator to ensure that the spark only happens at the tip.

This plug also has a perfect fit to remain sealed against high pressures. After all, it is located in the combustion chamber wall. 

There are different spark plugs: copper, platinum, or iridium. Sizes also vary in thread or nut, and the sealing types in taper or crush washer. 

What do glow plugs look like? 

Compared to spark plugs, glow plugs have more parts. It is a long and thin metal piece with an element of heating at the tip. This tip turns into a cherry-like color once the engine starts. 

The materials used to create a glow plug have features that resist oxidation and withstand high temperatures. 

Generally, the glow plug top parts are the following: bolt, round nut, insulation disc, o-ring seal, gasket, and plug body.

Meanwhile, below are the insertion thread, annular gap, glow tube, coil, insulating filling, and heating coil.

Can I use spark plugs and glow plugs interchangeably? 

No. Spark plugs and glow plugs have their unique usage and functions. If you have a gas engine, a spark plug is for you. However, check if you need a glow plug if you have a diesel engine.

Before buying a plug, know what to get for your engine because they can’t perform the same task.