Since I feature two diesel engine vehicles in my Youtube channel, I get all sorts of questions about diesel emissions and how to fix black smoke in diesel engines. As you know, it is quite normal for diesel engines to emit black smoke especially if one floors the pedal hard.
However, there are many cases that trucks and SUVs emits black smoke even when they just started their car or driving in low speed and low RPM.
Basically, common-rail diesel engines are designed to minimize black smoke emission while providing more horsepower and torque.
So why does diesel have this issue? And how to fix black smoke emission from diesel engines? Read on to learn more!
Types of “Diesel Smoke”
While any vehicles, petrol or diesel engines, emits poisonous gas into the air, people identifies black smoke as the worst of its kind.
Black smoke is not good to look at and has foul, health-sickening smell. That’s why people curse those vehicles on the road that emits black smoke.
But before I tell you how to avoid, lessen or fix black smoke from your car, let me give you some info regarding diesel engine smoke types. Because not all engines are created equal, you got to know the basics first.
Black Smoke
A car that emits black smoke surely has an underlying issue. After all, black smoke is a symptom of various failing car system. If your car has this symptom, don’t worry as you are not alone! Kidding, there are ways to fix the problem!
The common cause of black smoke is the imbalance in air-to-fuel ratio. This means too much fuel are being thrown in but not enough air to get the fuel burned. Mixing more fuel than air is a bad thing as more fuel gets unburn and exits the car as that deadly black smoke.
Studies suggest that diesel particulates are found in black smoke. Such particles should be burned in the combustion chamber for better fuel economy and engine power.
In contrast, black smoke can also triggered if an engine burns too much fuel.
White Smoke
Aside from black smoke, diesel engines (especially those new from the factory) also emits white smoke.
The common reason why a vehicle emits white smoke is the irregularities in the fuel burning process inside the combustion chamber. This means some amounts of fuel that is being injected are not burned properly as it should.
But there are other causes why diesel engines emit white smoke. This include low compression in fuel lines especially when the fuel pump timing is not in rhythm due to clog or something that prevents the fuel from getting into the pump (example is water).
Blue Smoke
While both black and white smokes are fuel-related symptoms, blue smoke on the other hand results from burning engine oil.
You probably thinking how can the oil escape into areas where it can be burned? Since the internal components inside the engine are mechanical, problems can easily occur even in just one slight miscalculations.
Such issues include faulty injector pump (lift pump), allowing the motor oil to get mix with fuel and gets burned together in the combustion chamber.
Bad valve stem seals are also common reasons why car emits white smoke. Worn cylinders and piston rings which allows the oil to force its way into areas where it can be burned.
Or, having too much oil in the engine resulting to too much pressure inside that creates mechanical issues and hampers the engine’s power.
How to Lessen or Even Fix Black Smoke in Diesel Engines
As mentioned above that the main reason for black smoke in diesel engines is incorrect fuel-to-air ratio, or basically imbalance (more) fuel than air needed to complete a perfect combustion process.
Since we know the culprit, our job now gets a little easier. We only just have to identify the reasons why the engine doesn’t draw enough air to the combustion chamber. Lets me enumerate the possible fix one-by-one.
Fuel Injector Problems
The simplest and what most mechanics turn to when a black smoke problem is handed to them is the fuel injection system, specifically the injectors.
Since fuel-to-air mixture is imbalance thus resulting to black smoke, a simple injector timing can fix the issue. Faulty or worn fuel injectors won’t give you the best performance as the fuel doesn’t get converted into a harmless gas emission.
If the fuel injectors are found completely functional, then you will have to diagnose other mechanical engine components.
EGR System
Exhaust Gas Recirculation system is a process of “recirculating” blowby gasses from the engine, back to the combustion chamber to get burned again, thus resulting to a more eco-friendly emission.
A single or multiple EGR system issues will result to loss of power, high fuel consumption, fast engine temperature increase and of course, black smoke.
How? These blowby gasses are composed of nitrogen oxide (Nox) gas and some gaseous oil from the engine. Overtime, these substances accumulates and hardens in many parts of the air intake system (which I will discuss later) and to the EGR system.
A leaking, malfunctioning EGR valve or faulty EGR motor caused by too much carbon deposits (hardened oil) inhibits the air from entering the combustion chamber thus resulting to more fuel getting burned or unburned. You may need to clean, repair or replace the EGR valve or motor if you found out that this is the culprit of your car.
Air Intake System
Diesel engines are like us, they breathe as they need the right amount of air to perform at the optimal level. Air restriction can impede the performance and may also lead to engine troubles and issues like black smoke.
Air is critical for engine’s combustion process. So lack of air won’t burn the fuel that is being thrown by the fuel injectors.
What causes air restriction in diesel engines?
Air intake system is the responsible for drawing enough air into the engine and any issues from any parts of the system will cause black smoke or even worse.
The system is composed of air filter, mass air flow sensor (MAF sensor), throttle body and the intake manifold. Some cars are designed as force induction air intake system, so they commonly have turbochargers included in the system. Take a short read of my air intake system 101 tutorial here.
So to be able to get the right amount of air into the engine, you car has to have clean air filter, a properly functioning mass air flow sensor, a good throttle body and clog-free intake manifold. Any issues like carbon deposits, leaks, etc must have to be cleaned or repaired to avoid further damage to the engine.
What about the turbochargers? Well, turbochargers might be a good addition to a naturally aspirated engine but it also has its downsides.
First, a turbo doesn’t work at low RPM meaning that you have to reach a certain amount of time and speed before you get that extra power from your turbo. What does this have to do with black smoke?
When you accelerates from a stop, you have to reach certain speed before your turbo starts to spool up and that requires a lot of time, and you guess it – fuel!
So forcing your engine to go faster in a turbocharged vehicle won’t be a nice idea as it only adds a lot of fuel at low RPM. This dampens the life of your engine while you go blind the car behind you with black smoke.
Engine Deposits
New engines are of course free of imperfections and are their optimum peak performance.
However, like most engines, they degrade overtime due to accumulations of combustion-by-products like fuel deposits on the injectors, cylinders and combustion chambers. This is specially common in diesel engines as diesel fuel contains no detergent.
To prevent or lessen the impact of diesel fuel deposits, you need to add fuel cleaning additives to your diesel fuel on a regular basis. This will help clean the internal parts of your engine while reducing the amount of unburned fuel.
Below is some of the diesel fuel additives that are available in the market. Take note that the video is in Tagalog but has English subtitle.
Conclusion
There you have it! If you have a diesel car and you notice that it emits a lot of black smoke, then you might want to check each components above and try to fix it yourself.
Otherwise, get a professional mechanic and have it serviced as soon as possible! Thank you for reading and until next time!
