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What to Do about Diesel Engines Giving Off Black Smoke

October 23, 2014
By Jeffery White

Although diesel engines may be the most efficient currently available, they’re still susceptible to problems just like any other. This means you need to keep an eye out for telltale signs that all is not well under the hood. One of the most common dead giveaways that your engine is struggling is the presence of dark, black smoke coming out of your exhaust.

As you probably already know, diesel engines rely on an extreme amount of pressure to force ignition. This amount can easily be three times as much as the pressure found in gasoline engines, which is also why diesels don’t need spark plugs.

Diesel engines apply this pressure to the mixture of gasoline and air in their compression chamber. However, if the mixture isn’t perfect, you can have all kinds of problems. This is what black smoke should be telling you: an imbalance in your fuel to air ratio is present. Whether or not there is too much air or gasoline is not so clear.

The smoke is black because it’s essentially infused with diesel. The mismatched ratio is causing large particles of the fuel to get through the combustion chamber without getting ignited. Once they pass through the engine, they come out the exhaust as tainted smoke.

Of course, the larger issue this black smoke represents is that you’re not getting ideal fuel efficiency from your engine. You can’t be if so much of the diesel fuel you pay for (which is never cheap) is escaping through your exhaust unused. Without a doubt, your mileage is suffering.

What’s actually causing the ratio to become so off isn’t so easy to say. The most common culprits are faulty injectors or injector pumps. Bad air filters are also frequently to blame as they keep sufficient oxygen from being supplied to the combustion chamber. A defective EGR valve could be causing a clog that’s behind the black smoke too. Sometimes it could even be an issue with the turbocharger.

Fortunately, most of these problems are no reason to start getting worried. They can be quickly addressed by a professional mechanic and, best of all, done so affordably. However, the longer you let that black smoke go unnoticed, the worse the problems are going to become and the more money you’ll be wasting on diesel fuel. Keep an eye on your exhaust pipes throughout the year, then, and if you see black smoke, take your truck in immediately.

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