4 Causes of Too Much Black Smoke from a Diesel Engine Exhaust
Modern diesel engines are no longer the sooty engines they once were. Although a black cloud of exhaust gas looks dirty, gasoline engines also emit invisible exhaust fumes. If a truck with a common rail diesel engine is running properly, smoke emissions will be minimal.
But excessive black smoke means something is wrong. This is not only bad for the environment, but also bad for your wallet. Let’s look at the most common causes of too much black smoke and how to fix the problem.
The 4 most common reasons for too much black smoke from the exhaust
1) Poor fuel supply
Over-fuelling is a common cause of black smoke in diesel exhaust. This occurs when too much fuel is injected into the combustion chamber and the excess fuel does not burn properly.
Look at the fuel supply system. Try the easy things first. Look at the injection control and EGR system. If there is an issue, you may need to replace the EGR valve. If this doesn’t fix the problem, it’s more likely a mechanical issue.
Diesel injectors play a key role in over-fueling issues. Worn injectors can cause enlarged nozzle openings or corroded injector needles, allowing more fuel into the combustion chamber.
Check your injectors. Incorrect valve clearance can cause the same problem, but this is rare.
2) Dirty or clogged air filter
A normal engine burns all the fuel, emitting water and CO2. Black smoke indicates that something is only partially burning the fuel, resulting in an incorrect air/fuel mixture.
Since diesel fuel only makes up part of the mixture in the combustion process, you need to look at the other part too – the air. If your engine is not getting enough air, the mixture will be too rich. h. This ratio favors the fuel. First check your air filter and replace it if it is dirty. If you are not getting enough air, you have found the cause.
3) Bad MAF Sensor
As mentioned above, a proper air-fuel ratio is important to ensure all the fuel is burned. Not only do you need to make sure your air filter is getting enough air, but you also need to make sure your vehicle’s computer is accurately measuring the amount of air coming in.
The Mass Air Flow Sensor (MAF) is responsible for making sure the proper amount of fuel is mixed with the air going into the engine. If the MAF sensor is faulty, it may record more airflow than is actually coming in.
4) Excessive Carbon Buildup
If your car is old and has high mileage, it can accumulate a lot of combustion products in critical areas and not function optimally. Diesel engines are prone to carbon buildup because they run long hours and diesel is a raw fuel that doesn’t use detergents from refineries.
In most cases, the solution is simple: add a detergent to your diesel fuel on a regular basis. My current favorite diesel engine additives are Liqui Moly Pro-Line Engine Flush and Hot Shot’s Secret Diesel Extreme.
