Can Glow Plugs Cause Smoke? (All You Need to Know)

Glow plugs are one of the most important parts of the diesel engine. The primary purpose of a glow plug is to help the combustion process in the diesel engine by controlling the temperature of air and fuel coming into the engine. 

Today, we are going to discuss and find out whether glow plugs can cause smoke or not. 

Can glow plugs cause smoke?

Glow plugs can often be the reason behind different colors of smoke coming out of the car’s exhaust pipe when they become faulty. Bad glow plugs can additionally increase the fuel consumption and decrease the overall performance of the car. It is not wise to drive with faulty glow plugs.

Let’s look at different colors of smokes and see if they are caused by glow plugs.

White smoke:

According to automobile experts, glow plugs have the ability to cause white smoke. For example, white smoke is often produced through the exhaust pipe when the glow plugs can not efficiently heat the incoming fuel into the diesel engine. 

A faulty glow plug is responsible for emitting white smoke out of the exhaust pipe.

Blue smoke:

It is believed by automobile experts that glow plugs can certainly cause blue smoke when they become faulty. Blue smoke is emitted when the engine oil and gasoline mix up together. Replacing the faulty glow plugs can effectively solve the blue smoke problem. 

Black smoke:

Black smoke can be seen emitting through the exhaust pipe because of a faulty glow plug. When the air and fuel mixture inside the diesel engine is not maintained by the glow plugs, then the black smoke is created from the combustion process inside the engine. 

Faulty glow plugs are one of the major reasons of black smoke coming out of the exhaust pipe. 

Gray smoke:

Just like the black smoke, gray smoke coming out of the exhaust pipe is also caused by faulty glow plugs because of inaccurate air and fuel mixture. 

When the presence of fuel inside the diesel engine is greater than the air, gray smoke is produced because of the combustion process. 

Will bad or faulty glow plugs cause smoke?

Glow plugs are fundamental when it comes to the function of a diesel engine. Diesel engine requires good glow plugs to complete the combustion process inside it. But if the glow plugs become faulty, then the combustion process gets interrupted and loses its preciseness. 

The glow plugs are tasked with the responsibility of controlling the temperature of air and fuel coming into the diesel engine. When the glow plugs fail to do that due to incompetence, it creates several colors of smoke in the combustion process.

White smoke is one of the primary smokes emitted through the exhaust pipe because of a faulty glow plug. Faulty glow plugs are also the reasons behind black, blue, and gray smoke coming out of the exhaust pipe. 

So it can be said that faulty or bad glow plugs will definitely cause smoke in the combustion process.

3 reasons why faulty glow plugs cause smoke

There are a lot of reasons why faulty glow plugs cause smoke. Let’s discuss in detail about some of them. 

Insufficient heating ability:

One of the major reasons why faulty glow plugs cause smoke in the combustion process is because of insufficient heating ability. 

If the glow plugs become bad or faulty due to any reason, then it will not be able to maintain the temperature of air and fuel entering the diesel engine.

When the diesel engine receives insufficiently heated air and fuel, it fails to produce a competent combustion process. As a result, white smoke is created from the combustion process and emitted out of the exhaust pipe. 

Inaccurate air and fuel ratio:

Faulty glow plugs can not control the flow of air and fuel inside the diesel engine. This gives birth to the inaccurate ratio of air and fuel inside the diesel engine. 

If the amount of fuel is greater than the air inside the engine, then the combustion process creates black, blue or gray smoke and emits it out of the exhaust pipe. 

Incomplete combustion process:

Another reason why faulty glow plugs cause smoke is because of an incomplete combustion process. If the glow plugs become bad, then the air and fuel going into the diesel engine are not mature enough to be participants of the combustion process. 

But the diesel engine has no other option other than conducting the combustion process which gives birth to an incomplete combustion process. 

What happens if glow plugs are faulty?

There are a lot of things that can happen if the glow plugs become faulty or bad. Let’s discuss in detail about some of the consequences of faulty glow plugs.

Engine misfires:

One of the major consequences of faulty glow plugs is an engine misfire. When the combustion process gets interrupted due to faulty glow plugs, the engine starts misfiring due to insufficient heat during the combustion process. 

The engine can not complete a combustion process without a temperature of four hundred and fifty degrees Fahrenheit (F) during the process. 

Smoke out of exhaust pipe:

Another consequence of faulty glow plugs is smoke coming out of the exhaust pipe. 

First of all, white smoke comes out of the exhaust pipe when the combustion process is incomplete due to the glow plugs’ ability to maintain the temperature of incoming fuel and air inside the engine. 

Secondly, you can also see black, gray, and blue smoke coming out of the exhaust pipe due to an inaccurate mixture of air and fuel inside the engine. The air and fuel mixture becomes inaccurate because of faulty glow plugs. 

Increased fuel cost:

Another major consequence of faulty glow plugs is the increase in fuel cost of your vehicle. When the engine fails to handle the combustion process effectively, there is a loss of fuel energy in the combustion cycle. 

This loss of fuel energy increases the fuel consumption of the vehicle. Faulty glow plugs need to be repaired or replaced to decrease the fuel cost. 

Overall poor performance:

The vehicle starts performing significantly bad when the glow plugs become faulty or bad. The acceleration of the vehicle will drop a lot because of faulty glow plugs. There is no other way except replacing the faulty glow plugs to gain the optimum performance of the vehicle. 

Can you fix glow plugs causing smoke?

It is possible to fix faulty glow plugs that are causing smoke. It is neither safe nor easy to drive your car with faulty glow plugs. The performance of your car will drop significantly if you keep driving with worn out glow plugs. It will additionally damage the other parts of the engine too.

First of all, you will need to check the condition of your faulty plugs with the help of a multimeter. If the glow plugs have gone beyond repairing, then you will need to replace them rather than repairing them. 

While replacing a single glow plug costs about one hundred USD, replacing the whole set of glow plugs might cost about five hundred to six hundred USD. 

How to fix glow plugs causing smoke?

Fixing glow plugs that cause smoke might seem like a difficult task if you have no prior experience regarding the matter. However, there are some steps and methods you can take to accomplish the task. Let’s discuss in detail about some of them. 

Locate the faulty glow plugs:

First of all, you will need to locate the faulty glow plugs of your car. You can test the condition of the glow plugs with a multimeter and replace the faulty ones or you can replace all of them at once for optimum performance. 

The glow plugs are situated at the area of the cylinder head most of the time. 

Detach the faulty glow plugs:

In the next step, you will be required to detach the faulty glow plugs from the cylinder head. You will have to detach the wires connecting the glow plugs to the engine with the help of a wrench. Then, you will need to detach the glow plugs by applying a ratchet. 

Get rid of dirt and dust:

You will need to get rid of dirt and dust from the glow plug wires before you attach new glow plugs to them. Carbon build up on the glow plug wires often hamper the performance of the glow plugs significantly.

Connect the new glow plugs:

You will need to connect the new glow plugs to the cylinder head using glow plug wires in the final step. Once again, a ratchet and a wrench will be helpful in this process. 

Final Thoughts

Bad or faulty glow plugs certainly have the ability to cause smoke in the car. Faulty glow plugs are the cause behind the incomplete combustion process inside the engine which creates black, white, gray, and blue smoke and dumps the smoke out of the exhaust pipe.