Are Glow Plugs and Injectors The Same? [Main Difference]

Glow plugs and injectors are not the same. Although they both contribute to one function, fuel combustion, they have completely different functions.

They are both parts of a vehicle’s engine system. 

The thing they have in common is that if you want your vehicle running smoothly, both of these components need proper maintenance.

They also need to be occasionally replaced because they deteriorate and experience wear and tear over time. 

Glow Plugs

A glow plug is responsible for the heating component of an engine. It heats incoming fuel and air in order to achieve proper fuel combustion, making starting and driving the vehicle possible.

This is only present in diesel engines as gasoline engines use spark plugs. 

Glow plugs use a metal coil to conduct the heat generated. It is enclosed in a metal tube and surrounded by ceramic powder.

The tip of these plugs can reach high levels of heat up to 1000 degrees celsius. 


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Injectors are little electrical parts that work to distribute fuel into the intake manifold by spraying. Without proper fuel distribution, the vehicle won’t properly function. 

The injector valves open and close at the exact rpm as the diesel engine, which is around 1800. It reaches approximately 150,000 times per hour.

For injectors to continue to run smoothly, there should be clean filters as well as optimal fuel quality. 

Main Difference

The main difference between glow plugs and injectors, other than their functions, is their necessity

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in a diesel engine. A diesel engine can possibly still function even without glow plugs. 

This is because diesel engines use air compression for fuel combustion. Meaning that the pistons are the ones that compress air and make it hot enough to ignite the fuel.

Additionally, the glow plug isn’t necessary for a diesel engine to function in warmer climates. 

Meanwhile, injectors are detrimental to engines. They are the ones that distribute and transfer fuel from the tank to the engine.

When injectors don’t function properly or, worse, aren’t in the engine at all, there is a 100% chance that the engine won’t run. 

Proper Injector Maintenance

You can improve the shelf life and performance quality of an engine’s injectors by following a few easy steps. 

Since the injectors deal with delivering fuel, it is important to observe the fuel quality. Clear fuel without foreign substances or sediments can prevent injectors from being clogged. High-quality fuel can also rid the need for additives. 

Cleaning the injectors can also help achieve peak performance. They should be cleaned every 25,000 to 30,000 miles or every time you have your vehicle serviced.

Lastly, if high-quality fuel is out of your budget, it is a fuel additive is a good alternative because they prevent gunk from forming and help in proper fuel combustion. 

Frequently Asked Questions

How much do glow plugs cost?

Glow plugs tend to cost $50 to $100. Generally, each cylinder of an engine needs one glow plug. When labor costs are added, a full set replacement of glow plugs costs around $450 to $600. 

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How much do injectors cost?

The cost of replacing the injectors of your vehicle depends on the type of injector and how many injectors your vehicle’s engine needs.

A good thing to remember is that each cylinder of an engine needs one fuel injector. Normally, a full replacement costs around $300 to $800 in shops. 

How often should injectors be replaced?

Injectors should be replaced every 50,000 to 100,000 miles, depending on how you use your vehicle. Unlike glow plugs, injectors can be serviced and cleaned.

When you perform consistent maintenance steps, you can improve the longevity of your engine’s injectors.

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