How Many Spark Plugs Does A Diesel Engine Have?

Published: 09/14/22 •  9 min read

The spark plugs are the heart of any gasoline-powered engine. These spark plugs are what create the engine’s energy. You might be curious about how many sparks plugs you have for your diesel engine.

Combustion (or burning) is a chemical reaction that involves heat and other elements. Diesel engines use glow plugs to heat the fuel and burn it during combustion (not spark plugs). Glow plugs “glow” when the engine is running, and there is one glow plug per cylinder. 

This article explains everything about spark plugs and glow plugs. Keep reading.

How Many Spark Plugs Does A Diesel Engine Have?

Zero Spark Plugs. Diesel fuel does not combust through sparks. So diesel engines do not use spark plugs. The diesel engine has a combustion system which eliminates the need to use a spark plug. Instead, it uses a glow plug, a different type of plug than the spark plug.

So, the better way to answer the question “How many glow plugs does a diesel engine have?” 

Although glow plugs are different, they serve the same purpose of burning fuel. One glow plug per cylinder is the obvious answer if you consider the similarities. One glow plug is present in most diesel engines. 

Diesel engines require zero spark plugs and only one glow plug per piston.

What is Spark Plugs?

How Many Spark Plugs Does A Diesel Engine Have?

Any gas-powered engine will have a spark plug. The spark plug ignites an engine spark. The spark further ignites fuel and air, which causes a small explosion within the engine’s valves. The explosion causes the piston to fall from your engine, creating energy that propels your car forward.

Diesel engines produce energy in a different way than gasoline engines. They don’t need a spark. They rely on heat from a plug instead. Each cylinder has one spark plug in most engines

What are Glow Plugs?

A glow plug is a heating device that ignites the fuel/air mixture within the engine’s pistons, much like a spark plug. Each cylinder in a diesel engine has a glow plug.

It is made of metal and has a heating element at its tip. When heated, it emits light. The glow plug is where diesel is sprayed. It reacts with compressed air and evaporates to start the combustion process.

How Do Glow Plugs Work?

Diesel engines use high pressure to compress the air. The compressed air is sucked into a cylinder. The high pressure raises the temperature to ignite the diesel when the fuel is added at the end. The gases expand once the diesel gets ignited and the power stroke begins.

The glow plug heats the diesel engine in three phases. The three-phase system ensures that your engine has sufficient heat to ignite and produce energy for your vehicle. The three phases are –

Different Types of Glow Plugs

The glow plug is an electric heating device found in every diesel engine cylinder. It has a tip heating element that emits light when heated. The heated tip heats up when die

sel is sprayed. It mixes with the compressed oxygen, evaporates, and then starts combustion. This is why the glow plug replaces a spark plug.

You need to consider a few things when choosing the right glow plugs for your diesel engine. There are three types of plugs: hot, medium, or cold. When purchasing new plugs, you will need to determine the nitro percentage, engine size, engine type, and acceleration.

For small engines, a hot glow is required. Large engines can use colder plugs. Use hot glow plugs to accelerate or improve sluggishness. Based on the engine type, turbo engines might require special glow plugs. A higher nitro percentage will result in a cooler glow plug. A hot glow plug is made with a lower percentage of nitro-percentage. Cold plugs are more powerful and can produce more torque.

#1. Pressure Sensor Glow Plugs

These plugs include a pressure sensor integrated into them that can increase the efficiency of your engine. The sensor sends pressure readings to the engine control unit. Moreover, it reduces your vehicle’s emissions, makes it easier to start your car in cold weather, and increases fuel economy. 

#2. Steel Glow Plugs

Steel plugs are also reliable and efficient. Although they take longer to turn on, but will not have any problems starting your car in freezing temperatures.

#3. Ceramic Glow Plugs

The best efficiency for most vehicles is possible with ceramic plugs. They heat quickly and reach higher temperatures than their counterparts. They ensure that diesel fuel burns at its best, and you can start your car even in cold weather.

How Often Do You Change Diesel Glow Plugs?

For optimum engine performance, it is essential to replace glow plugs. Replacing glow plugs is affordable and straightforward. Most glow plugs will last for at least 100,000 miles on average.

Different maintenance schedules may apply to different vehicles. To determine the best time to do scheduled maintenance, you can refer to the owner’s manual. It is a good idea to check your glow plugs every 12,000 miles. You should replace all plugs in your engine when replacing a damaged one. This will ensure that each cylinder provides optimal performance.

It is simple and not too expensive to replace glow plugs. Most amateur mechanics can install new glow plugs in their garage or driveway or get them replaced by a professional mechanic.


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The Bottom Line

Many car owners may assume that their diesel engine needs to spark plugs. But diesel engines use glow plugs. You will require one glow plug for each cylinder, regardless of the size of your diesel engine. You can determine how many cylinders your vehicle uses by consulting the manufacturer guide.