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White Smoke From Diesel: 6 Common Causes & Fixes

If you notice white smoke coming from a diesel engine, there is one main reason: the fuel isn’t burning the way it should.

Though this one reason can be the primary diagnosis for the diesel engine problem, several things can cause this, and if you want to do a self-diagnosis, it may also be good to know how to fix these problems.

Causes For White Smoke From Diesel Engine:

  1. The fuel injectors are faulty or broken
  2. Incorrect injector timing
  3. Water or coolant contamination with fuel
  4. Fuel has a low Cetane rating
  5. Your engine or weather is cold
  6. Blocked or dirty fuel filter

Let’s go through each of these common causes and how to solve them.

1. The Fuel Injectors Are Faulty Or Broken

Fuel injectors have the task of giving fuel to the combustion chamber at the perfect time and in the right amount for the engine to work correctly.

If the injectors do not allow the right amount of fuel into the chamber, there may be white smoke from the exhaust because the fuel struggles to burn the way it should.

There may be a build-up of debris on the fuel injectors, which may cause them to inject improper doses of fuel into the combustion chamber.

However, there is also the chance that the fuel injectors are broken or faulty for other reasons, which can cause the same result of white smoke emanating from the diesel engine exhaust.

The Solution

Fuel injectors are usually not too overpriced or hard to replace, so if you are confident that this is the problem, you should replace them as soon as possible.

You can also take your car or generator to a mechanic to see if they would be able to do it for you if you are uncertain of your ability to do it yourself.


  • Injectors may get clogged
  • Injectors may malfunction
  • Buy and replace injectors
  • Or have a mechanic fix it

2. Incorrect Injector Timing

As stated above, the injectors have the job of supplying the fuel to the internal combustion chamber, which they have to do at precisely the right time for the engine to work as it should.

If the injection timing is even a little bit delayed or early, this may cause the fuel not to burn as it should, which can be another cause of white smoke coming from the engine.

There are a few reasons why the injection timing could be wrong, one of which is that a blockage prevents the injection from happening at the right time. There is also the chance that the problem lies with the pump.

Along with white smoke, there may also be other issues with your diesel engine if this is the problem, such as inefficient fuel consumption and loss of power.

The Solution

There are a few things you may need to consider to solve the problem of injection timing, one of which is replacing the injectors if they have blockages that are throwing off the timing.

The other option is a bit more tricky and expensive, replacing your injection pump if the injectors are still in good working condition.

If you are comfortable working on engines or feel like you can do it yourself if you have the right help, there are videos online that can help you make replacing the pump a bit cheaper by reducing labor costs.

However, if you are unsure what to do or would prefer a professional’s help, you may be better off going to a mechanic.


  • You may need new injectors
  • Or the pump may be the problem
  • There are videos online to help you replace the pump
  • You may prefer going to a mechanic

3. Water Or Coolant Contamination With Fuel

Another reason there may be white smoke from your diesel engine, and a common reason the fuel may not ignite the way it should, is contamination with water or coolant.

Though the coolant in your engine is supposed to keep the engine running at ordinary temperatures, there are reports of coolant or water leaking and making its way into the combustion chamber.

If you are afraid that this may be the case for your diesel engine, there are a few indicators you can look for to be sure.

The smell may be the first thing you notice if coolant leaks into your combustion chamber and causes white smoke. Some say that when the coolant mixes in the combustion chamber, it causes a semi-sweet smell which is easy enough to pick up on.

Another thing you can look for is residue in or under the engine. The residue’s color is usually green and may also be sticky.

The last thing you should note is that your engine may start running hotter than usual, and you may need to top-up your coolant more often; both of these are signs that the coolant may leak and cause white smoke if it contaminates the fuel.

The Solution

If your car is leaking water or coolant, it may be better not to drive it around or do something risky.

The best method for fixing this is by asking a mechanic or professional for help since driving the car may cause damage to other components if the coolant leak is the cause of the white smoke.


  • Coolant may leak into the combustion chamber
  • Fuel contamination can lead to white smoke
  • The best and most accurate fix is getting professional help

4. Fuel Has A Low Cetane Rating

The cetane rating of diesel is a significant factor concerning white smoke since it affects the time between the fuel being injected and ignited.

The ratings of other fuels, like the usual gasoline, ensure that there is no ignition before the fuel gets sparked in the chamber; however, for diesel engines, the fuel has to ignite without a spark, which is why higher cetane ratings are better for the engine.

The lower the rating is, the longer it takes for the fuel to be able to ignite, which in turn causes the engine to become less efficient and can also cause white smoke in a similar way that a faulty injector may.

Though a low cetane rating may cause white smoke, it is not a permanent fault with the engine, and the solution is straightforward.

The Solution

The easiest way to ensure your engine does not produce white smoke due to low cetane ratings of the fuel you use, you should use fuel with higher cetane ratings.

Doing this may be a bit more expensive since higher cetane ratings usually mean you need to buy premium diesel. Using a higher quality fuel can also help the engine run more efficiently and for a more extended period.


  • Low cetane ratings cause fuel not to ignite when it should
  • The best solution is to use higher cetane-rating fuel

5. Your Engine Or Weather Is Cold

It is common for a car or other engine to produce white smoke when the engine is still cold or has just started.

The low temperature of the engine causes the cylinder walls to become wet, and the lack of heat means that the fuel struggles to evaporate as it should, which can cause white smoke to come out of the exhaust.

Similar to the effects of low-quality fuel and injection problems, the engine’s efficiency is lower when the engine starts, which is why it may emit white smoke.

There is also a chance that the white smoke from a cold diesel engine is simply condensation that has built-up and now has to evaporate as the engine starts up; this white smoke will likely stop once the engine heats up properly.

During colder times, it is more common to see white smoke from a diesel engine, but this is usually only when the engine is still cold since the heat of a warmed-up engine does not allow much condensation.

There is also the chance that white smoke may continue while driving in cold weather since it is not too uncommon for a small amount of evaporating fuel to freeze once it gets ejected into the air.

The Solution

White smoke coming from a diesel engine on start is usually not a sign of the engine malfunctioning or the need to replace or fix any part of the engine.

This process is relatively standard and is more common in cold areas. The only way to eliminate the white smoke produced by a cold diesel engine is to allow the engine time to heat up and allow the condensation to evaporate around the affected areas.

In addition, if you stay in a colder region and there is white smoke coming from the engine even when the engine is heated, this may be due to the cold weather.

If you are uncertain if the condensation or weather is the cause of the white smoke, it may be better to ask a professional or mechanic for help to be sure.


  • When an engine is cold, white smoke is not a sure sign of a fault
  • White smoke is also typical in colder weather
  • There may be no need to be concerned if the smoke stops
  • If you are uncertain, a mechanic may be able to help

6. Blocked Or Dirty Fuel Filter

The filters in an engine are essential to ensure the intake of air, fuel, and other necessary components are clean and work as intended.

However, over time the filters, including the fuel filter, may become dirty or clogged, which can lead to white smoke from the diesel engine.

There are many reasons why your filter may become blocked or dirty, and it is essential to keep an eye on the filter and clean or replace it when necessary to ensure the filter still does its job.

The first reason your filter may become dirty or blocked is prolonged use without cleaning or replacements, which is a common occurrence since many people forget to check their filters.

There is also the chance of rust building up inside your engine or fuel tank, which may cause the filter to get dirty or blocked much faster than it usually would.

Another essential thing to note is that contamination of the fuel with other liquids, such as coolant or oil, may cause the filter to get blocked sooner than expected, so it is essential to change the filter if any contamination happened in the past.

If the fuel filter is blocked or dirty, it may allow some fuel to reach the combustion chamber unfiltered, which is one reason it may create white smoke.

Another reason it may create white smoke is due to an unbalanced amount of air and fuel reaching the chamber. If there is a significant blockage in the fuel filter, this may cause the fuel to slow down or not be able to reach the chamber in due time.

The Solution

Though the fuel filter may cause a lot of white smoke, this is an easy enough repair to make, and most people will be able to do it themselves unless the engine is particularly complicated.

To stop the white smoke due to a blocked or dirty filter, you can replace the filter or clean it if you know how.

In addition, if you are uncertain of how to replace the fuel filter or fear you may make a mistake, you can also request help from a professional or a mechanic to help you or replace the filter.


  • A dirty or blocked filter may cause unbalanced fuel and air in the combustion chamber
  • The filter may also allow unfiltered fuel into the chamber, which can cause smoke
  • You can clean or replace the fuel filter easily
  • If you are uncertain of what to do, contact a mechanic or professional for help