# Black Smoke from Diesel Exhaust ?



## Overboard (Feb 20, 2008)

What causes the black smoke from the diesels when you hammer on it or when using the passing gear? I am not a mechanic but was driving home yesterday and this guy in a white dually was pouring some black smoke everytime he stepped on it.


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## POMPANO (Oct 21, 2005)

*ROLLIN THE COAL!*

Excess fuel not being completely burned.


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## Arlon (Feb 8, 2005)

He had a "performance" chip that was simply dumping in more fuel than the truck could effeciently burn. He was making 10% more power but probably burning 20% more fuel to do it. Watch a diesel tractor pull sometime if you want to see some smoke..


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## Pocketfisherman (May 30, 2005)

Too much fuel, not enough air. Could be a leak downstream of the turbo or the intercooler bleeding off boost. On older Cummins with the mechanical bosch pump, it could be the tracker valve that regulates fuel against boost. It is adjustable if you remove the cover on the pump. Could also be the truck was chipped or tuned and was overfueling.


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## Overboard (Feb 20, 2008)

I too have a diesel but have never really paid any attention to this until last night- coming home from my sone bb practice, I passed a lady in a little car- looked back and could see that poured some smoke on her car- Just got me to thinking and hoping/oraying nothing was wrong witht eh truck. has about 270k miles on it F250- I've had it for about 10 yrs now.


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## ScottK (Mar 24, 2010)

Up until the invention of the "wonderful" DPF filter all diesel's would blow smoke, and its not the black smoke you worry about it's any other color.... like white. If a truck has a programmer or chip it will smoke more due to the increase in fuel rail pressure.


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## bwguardian (Aug 30, 2005)

It is not only excessive unburt fuel but also buildup...I used to be able to throw black smoke when I put my foot in the throttle. Since I have been burning biodiesel for the last 4 years the only time it does it is after about 500 miles if I drive it with a light foot then nail the throttle. My wifes Excursion was driven on the highway 90% of the time by the previous owner when we got it 6 years ago and it took a year to blow the junk out of the exhaust.


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## gitchesum (Nov 18, 2006)

I would also go with the idea that it was some kind of programmer or power box. They give more bottom end fuel, so if you get into the accelerator too hard at low RPM's, it will belch out the excess fuel. The excess fuel actually burns after it leaves the combustion chamber hence the black smoke(just like burning diesel on a campfire).

Personally, I don't care for it myself. It's kind of a side effect of the performance upgrade. I have a 230HP programmer, as well as a set of 150HP injectors, and my truck smokes very little for the kind of power it is making.

Granted, I don't run the programmer at the higher setting for just daily driving. but even at lower settings, I can still make a considerable amount of smoke. I drive my truck in a manner that it smokes very little, if any at all.


Some people simply like to make smoke, which seems kinda dumb to me. Heck, our little pro-street drag truck that runs 10 second 1/4 miles makes less smoke that some of these guys I see on the streets.


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## captMATT (Jun 3, 2005)

pure power from the pits of the diesel, gotta love it.


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