Black smoke on decelleration

[snoman87]

Just trying to tweek my IP a little bit for better fuel economay. Right now I get black smoke when I let off the accelerator. There doesn't seem to be any when I a press down, but definately when I let off.

Should I turn the pump down a little?

[More Power]

Since no one has replied, I thought I'd push this back to the top.

Fuel metering inside the injection pump with the accel pedal at idle shouldn't allow for the engine to produce black smoke. Unless you have some sort of fuel injection pump issue going on, I don't know what the problem might be. :confused:

Jim

[CleviteKid]

If your truck is DE-celerating, then the engine is not even making enough power to maintain speed. So the total amount of fuel being put into the engine is reduced. All that comes to mind is that one cylinder is getting a lot of fuel while the other seven are not, and the over-rich cylinder is making some black smoke.

You do, I believe, need to get your injection pump and injectors checked. There is a general consensus that past 75,000 miles, a set of injectors can become questionable. And yes, I know that there are examples of injector sets that have gone x00,000 miles, where x is an integer. Normal variation.

[dieseldummy]

My 6.5 used to do the same thing on occasion, my 6.2 doesn't. My WD-9 IH tractor also does it. I have a hunch it has something to do with timing, but have no hard facts.

[snoman87]

i suspect timing has something to do with it to. I retarded the timing slightly and is doesn't seem to make as much black smoke ... think I am still going to turn down the IP fuel metering and bump the timing back up slightly. On a positive note, the truck does seem to be running slightly better

[Bnave95]

i suspect timing has something to do with it to. I retarded the timing slightly and is doesn't seem to make as much black smoke ... think I am still going to turn down the IP fuel metering and bump the timing back up slightly. On a positive note, the truck does seem to be running slightly better
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[snoman87]

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Fixed ... thanks