How Many Spark Plugs Does A Diesel Have?

Diesel engines and gasoline engines have significant differences and individual features. Spark plugs are mostly seen in gasoline engines and they play an important role to start the engine. But what about diesel engines? How many spark plugs does a diesel engine have?

Diesel engines do not have spark plugs; instead, they have glow plugs which act almost the same as spark plugs. The number of glow plugs in a diesel engine is just the same as the number of cylinders in the engine. So, if there are 8 engines in a cylinder, the engine will have 8 glow plugs.

Now, let’s get to the whole article so you don’t leave this page with any confusion regarding the topic. We’ll discuss everything including how the glow plugs differ from spark plugs, how the glow plugs function, and so on.

How Many Spark Plugs Does A Diesel Have?

Diesel engines do not have spark plugs like gasoline engines, they have glow plugs instead. It’s because the ignition of gasoline and diesel fuel are different. However, the role of both spark plugs and glow plugs in the ignition are the same.

If things seem confusing, let me clear it up now. Spark plugs ignite the gasoline engines and help them create energy to start your car. Similarly, glow plugs are used to start the engine.

But the way they start the engine has a difference.

In gasoline engines, the combustion process easily starts by igniting the gasoline inside the chamber. But the ignition of diesel fuel is not as simple as that.

Just a small spark from spark plugs isn’t enough to start the ignition. For this, the glow plugs heat the area extremely fast; they can reach up to 1000℃ temperature within a few seconds and start the ignition process.

Because of the ceramic coatings on glow plugs, they can heat up significantly more quickly. And, they not only heat the diesel fuel but also heat up the entire engine for the appropriate operation from the start.

The Number Of Plugs

Simply put, your diesel engine has the same number of glow plugs as its cylinder number. For instance, if your engine has 6 cylinders, there are 6 glow plugs in your diesel.

How many glow plugs a diesel engine has depends on the engine manufacturer. In many new engines, the glow plugs are combined with other parts like the fuel injector.

The numbering system is also the same regarding the number of spark plugs in a gasoline engine. You’ll find spark plugs in every cylinder of your gas engine, meaning there would be 6 spark plugs in a 6-cylinder engine.

What Are The Differences Between Spark Plugs and Glow Plugs?

Let’s have a quick look at the differences between spark plugs and glow plugs.

FactorsSpark PlugGlow Plug
LocationIt locates in the wall of the combustion chamber.It locates in each cylinder of the diesel engine.
LookIt has a central conductor that’s surrounded by an insulator.It’s a thing and a long piece of metal and there’s a heating element at its tip.
Working timeSpark plugs work continuously while you drive.It only works during the ignition process.
Working processSpark plugs produce a lot of sparks per minute to keep the fuel mixture lit.It electrifies the heating element so it can heat up and emit visible light.
Plug requirementSpark plugs are a must to ignite the engine every time you want to drive.Diesel will ignite even without a glow plug if the engine or the day is warm enough. 
Spark plugs vs Glow Plugs

So yes, although new car owners find it hard to differentiate glow plugs from spark plugs, there are significant differences between the plugs.

What’s The Function of Glow Plugs?

In short, glow plugs to heat up diesel engines quickly, keep the temperature balanced and keep the engines heated as long as needed. In detail, they function in three phases.

  • Pre-ignition phase: As soon as you turn the ignition ON, glow plugs to heat up the cylinders. However, if you have an older car, the duration might be longer than the newer one.
  • Ignition phase: Glow plugs create optimal combustion and ensure a healthy engine starts every time you drive.
  • Post-ignition phase: The plugs will keep working as long as the engine heats up.

How to Choose The Right Glow Plugs

Glow plugs also have different types like spark plugs. Which one you should go for depends on factors like your engine size, engine type, acceleration, and nitro percentage.

High nitro-percentage will require colder glow plugs whereas low-percentage one will need a hotter glow plug. And, if your car has a turbo engine, it will require a specific glow plug depending on the engine and manufacturer.

People who want to improve the sluggish performance of their engines and want acceleration should get hot glow plugs. On the other hand, you’ll get higher power and torque using cold plugs.

Moreover, cars with small engines generally require hot glow plugs and large ones require colder plugs.

Types of Glow Plugs

There are three different types of glow plugs as follows.

  • Pressure Sensor Glow Plugs: There’s an integrated pressure sensor in these plugs that improve the engine’s efficiency. The piezoresistive sensor delivers the pressure reports in the cylinder to the engine control unit.

The plugs help your car to start in the cold more easily and the overall fuel economy is also improved. Moreover, they lower the emissions of your car as well.

  • Ceramic Glow Plugs: If you want a glow plug that heats up super quickly, these are the right types. They can heat up to 1300℃ within a few seconds.

This quality makes them useful to quickly start your car in even the coldest weather conditions. Diesel fuel will burn in just the right condition when you use the plugs.

  • High-Tech Steel Glow Plugs: These plugs offer a three- or -two-stage glow system. They can take quite long to start but you won’t struggle to start your car under extremely cold conditions while using steel glow plugs.

Inline Cylinder Engine

We can all notice this engine in vehicles which were available before 2000. The arrival of the V engine has declined the use of the inline motor. Generally, this engine has the cylinder in a row. And three and four cylinders are the most prevalent ones. The spark plugs are on the top of each cylinder of the engine. 

V Cylinder Engine

Today we can observe the V-cylinder engine in almost all the vehicles and other transportation systems like aeroplanes, submarines, marines, etc. However, if we consider the cars only, the V 4, V 6, and V 8 engines are the most prevalent. 

Here are some spark details of these diesel engines. 

Single V Engine

Generally, the number of sparks in the single V engine is one. And there is only one cylinder also. The first diesel engine included one cylinder and one spark. 

V 4 Engine

The most prevalent engine in today’s age is the V 4. Generally, we can find this engine in all medium-sized vehicles. The number of sparks and cylinders in this engine is 4. And the spark plugs generate the sparks continuously, one after one. 

V 6 Engine

We can find the V 6 engine in SUVs and robust sedan cars. In this engine, the number of cylinders and spark plugs is 6. The spark plugs generate sparks frequently here, one after one. But in some engines, the pins maintain an array to create sparks. 

V 8 Engine

We can find the V 8 engines in all the luxurious vehicles like Mercedes-Benz, BMW, Rolls-Royce, etc. The number of spark plugs and cylinders is 8, which frequently run while maneuvering. The spark plugs maintain an array to generate the sparks since it enhances the engine’s robustness. 

How Many Spark Plugs Does A Diesel Have_ Infographic


1. Do diesel engines have spark plugs?

Answer: No, diesel engines come with glow plugs that act almost the same as spark plugs. Instead of producing sparks in the combustion system, glow plugs increase the temperature and the ‘heat-up’ helps the engine to start.

2. How many spark plugs are in a gas engine?

Answer:  The number of spark plugs generally depends on the number of cylinders. If an engine has 2 cylinders, the number of spark plugs will be 2. If it is a 4 cylinder engine, the number of spark plugs will be 4.


Although spark plugs are one of the most crucial factors in gasoline engines, diesel engines do not require spark plugs because they need glow plugs to work. 

So, you’ve got a detailed answer to the question- “how many spark plugs does a diesel have?” Hopefully, now you can understand whether your car engine has spark plugs or glow plugs and how many glow plugs are there.

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William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

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Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at with a passion for the automotive industry.