Black smoke at start up and heave accl. Back firing when turning off engine.

[pedigo78]

I have noticed in the past few days that my truck on start up has been putting out more black smoke than normal. And of course when i floor it, it has a ton of black smoke. I have also noticed every once in awhile it back fires when i turn it off. I know that my carb needs to be turned but have no clue how to do that. I live in quantico VA. anyone around here know how to do it?

[beastie_3]

black smoke is unburnt fuel basically, I wouldnt touch your carb yet, but look at your ignition first. How old are the ignition components? Maybe pull the plugs and check their color too. might narrow it down to a cyl.

[DnStClr]

You know sarge, it's not really normal to have any black smoke at start-up. So you're going to have to get a tune up for starters. Do you have access to a timing light?

[pedigo78]

No I dont have access to a timing light. But I will take a look at my spark plugs. I have all MSD in the truck.

[1979C20]

I have also noticed every once in awhile it back fires when i turn it off.

sounds like your truck is dieseling. Which would be a timing problem.

[jaredts]

Black smoke and backfiring could also be a wiped out cam lobe.  I think if it were me I would pull the plug wires off one at a time while its idling and see if there's one cylinder that's the culprit (one that doesn't lower the rpm's much).  Then you can pull the plugs and compare and see if that one looks different.  Make sure of obvious stuff, though.  Inspect your wires for burned spots, check for vacuum leaks, etc.  Cranking up your idle speed screw on the carburetor to make up for vacuum leaks is one cause of dieseling.  Lots of things to check, just in what order?