{"id":744,"date":"2021-10-06T18:38:49","date_gmt":"2021-10-06T18:38:49","guid":{"rendered":"http:\/\/localhost:10008\/?p=744"},"modified":"2024-03-15T15:23:10","modified_gmt":"2024-03-15T15:23:10","slug":"rolling-coal-the-causes-of-black-smoke-from-a-diesel-and-what-to-look-for","status":"publish","type":"post","link":"https:\/\/learndiesels.com\/rolling-coal-the-causes-of-black-smoke-from-a-diesel-and-what-to-look-for\/","title":{"rendered":"Top Causes of Black Smoke in Diesel Engines"},"content":{"rendered":"\n
So, you have some black smoke billowing out of your exhaust. Otherwise known as \u201crolling coal\u201d. Nothing more fun to a diesel guy than seeing a Prius with the windows down and blowing a bunch of black smoke that way. Diesel engines are known for blowing black smoke during acceleration but, is that bad? Is it a sign of trouble? What causes black smoke? Let\u2019s answer those questions and more.<\/p>\n\n\n\n
What does Black smoke from a diesel engine mean?<\/em><\/p>\n\n\n\n
When you see black smoke billowing out of a diesel engine, it’s a sign that not all of the fuel is being burned properly. Normally, diesel engines are designed to completely burn the fuel, which results in the emission of water vapor and carbon dioxide. Black smoke, on the other hand, indicates an issue with the air-to-fuel mixture, which causes only partial combustion. <\/strong>This can be caused by various factors, including a dirty air filter, low engine operating temperature, or excessive fuel being added. In any case, it’s important to address the issue promptly to ensure your diesel engine runs smoothly and efficiently<\/p>\n\n\n\n<\/figure>\n\n\n\n
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Whether or not is bad for your engine depends on what the cause of the black smoke is.\u00a0A little black smoke is normal on a properly functioning diesel engine<\/strong>, but if the number of smoke changes at different RPMs and loads you have an issue. Here are the things it could be and then we will go into what to look for and the steps to diagnose the problem\u2026<\/p>\n\n\n\n
Causes of black smoke (In no particular order)<\/h2>\n\n\n\n
\n
Incorrect timing<\/li>\n\n\n\n
Dirty, worn or malfunctioning injectors<\/li>\n\n\n\n
Over-fueling<\/li>\n\n\n\n
Faulty turbocharger<\/li>\n\n\n\n
Incorrect valve clearance<\/li>\n\n\n\n
Incorrect air\/fuel ratio<\/li>\n\n\n\n
Low cylinder compression<\/li>\n\n\n\n
Dirty air cleaner<\/li>\n\n\n\n
Restricted induction system<\/li>\n\n\n\n
Carbon in intake manifolds<\/li>\n\n\n\n
Incorrect engine tune<\/li>\n\n\n\n
Poor quality fuel<\/li>\n\n\n\n
Excessive carbon builds up in the combustion chamber<\/li>\n\n\n\n
Cool operating temperatures<\/li>\n<\/ul>\n\n\n\n
Let\u2019s start as always with the most likely problems first ????\ufe0f\u200d<\/h2>\n\n\n\n
Air Restriction<\/h2>\n\n\n\n
There is a delicate mixture of air and fuel that needs to be achieved in order to have a clean burn from your diesel engine. When you are having black smoke, the balance has not happened.\u00a0Air restriction is the most common cause of black smoke.<\/strong>\u00a0So, where is the restriction?<\/p>\n\n\n\n
1. Air filter<\/strong><\/p>\n\n\n\n
First, you’ll want to check the air filter and make sure it’s not dirty or clogged. If it is, replacing it with a clean one will help improve the airflow to the engine and reduce black smoke. If the air filter looks fine, the next step is to check the injectors. Over time, diesel fuel can leave deposits on the injectors, causing them to clog and reduce the amount of fuel that’s burned in the combustion chamber. Cleaning or replacing the injectors can often solve the problem of black smoke.<\/p>\n\n\n\n
How dirty is it? When is the last time you opened it up and looked at it? Sometimes there is what is called a \u201cair minder\u201d.It is an indicator for your air filter and should be changed when it reaches a specified mark. That could be it! and a majority of the time this is the problem.<\/p>\n\n\n\n
2. Inlet restriction<\/strong><\/p>\n\n\n\n
Check your inlet piping. Is one collapsed? Look for anything abnormal in the housing. Run the engine while you are looking at a weak hose that may suck together when operating. What about that missing shop rag ????? Anyway, you get the idea. Look for obstructions to air freely flowing into the engine intake.<\/p>\n\n\n\n
3. Leaks or damage around or in the turbocharger<\/strong><\/p>\n\n\n\n
Look at all the piping around the turbocharger and intercooler. Listen when the engine is under a load and sometimes it will squeal and let you know that there is a leak somewhere. Tighten all the connections. They can always use a little quarter turn. Listen for abnormal noise from the turbo itself. When you have the hose removed give the turbine and wiggle. It should have only a small amount of \u2018play\u2019.<\/p>\n\n\n\n
4. Exhaust or DPF damaged<\/strong><\/p>\n\n\n\n
Inspect the entire exhaust and DPF system. Look for any crushed or damaged parts. Look at the muffler if it\u2019s under the vehicle. It is easy to damage when you have a driver who likes running over things.<\/p>\n\n\n\n
5. Sensor faults<\/strong><\/p>\n\n\n\n
Modern engines have control units that actively measure air mass and make appropriate adjustments. You could have a sensor giving bad information to the module.<\/p>\n\n\n\n
Fuel or Tune<\/h2>\n\n\n\n
1. Poor Driving<\/strong><\/p>\n\n\n\n
You are going to see this in manual transmission vehicles. If the gear is too high for load and the driver attempts to just give it more fuel the engine will inject more diesel and there will not be enough air for the engine to burn the diesel fully. This doesn\u2019t mean that the engine is malfunctioning; it just means that the driver needs training.<\/p>\n\n\n\n
2. Bad Fuel<\/strong><\/p>\n\n\n\n
Check your fuel quality. Bad fuel can cause all sorts of issues. Be careful where you fuel up and pay attention as best as you can to the fuel you are putting in. It is no fun draining tanks. A great place to check fuel quality is to drain your fuel filter. Note: kerosene emits black smoke<\/p>\n\n\n\n
3. Bad tune<\/strong><\/p>\n\n\n\n
Has your fancy tune betrayed you? You may just need to reset your tune if you are not intending to blackout everyone at every stoplight. Maybe you lost power and it reverted to an incorrect tune. Worth looking into if you are having issues.<\/p>\n\n\n\n<\/figure>\n\n\n\n
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Mechanical Issues (So much for the easy stuff)<\/h2>\n\n\n\n
1. Injector timing<\/strong><\/p>\n\n\n\n
It could be that your injector timing needs adjusting.<\/p>\n\n\n\n
2. EGR issues<\/strong><\/p>\n\n\n\n
Look at the specific steps to inspect and test your EGR system. Make sure the EGR valve doesn\u2019t need to be replaced.<\/p>\n\n\n\n
3. Faulty injectors<\/strong><\/p>\n\n\n\n
Dirty, sticking, or leaking injectors. Common rail injectors stay open for too long giving the engine too much fuel. One thing you can do to determine this is to measure the temperature of the exhaust manifold at each cylinder. You are looking for cooler temperatures in certain cylinders to indicate the fuel is passing through unburnt.<\/p>\n\n\n\n
4. Incorrect Valve Lash<\/strong><\/p>\n\n\n\n
This can happen when you have had damage to the top of the engine or a recent repair where the overhead was run. This can be indicated by a \u201crattle\u201d ????under the valve cover. It is easy enough to pop the cover off and have a look.<\/p>\n\n\n\n
5. Cylinder problems<\/strong><\/p>\n\n\n\n
Worn or sticking rings can cause low cylinder compression, and excessive carbon built up in the combustion chamber can all be the cause. This can be indicated by excessive blow-by. Diesel engines are prone to this over time because they typically run for longer periods of time and diesel fuel doesn\u2019t include any detergent from the refinery. This can be avoided by adding a\u00a0detergent additive (Links to Amazon)<\/a>\u00a0to your diesel fuel on a regular basis.<\/p>\n\n\n\n
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