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May 30, 2003 | 06:22 PM

john7979

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From: south jersey

too rich

I recently bought a 79 F250 with a straight six it had been sitting for a few years before I bought it. I got it running and ran some fresh gas and carb cleaner through it but it blows heavy black and gray smoke and runs real rough at idle. I changed the plug wires, fuel filter and oil but it still runs bad seems to be burning way to much gas I turned the mixture screw all the way in and took the carb apart to see if the float was sticking open but no help. any ideas what could be doing this?

thanks

John

May 30, 2003 | 11:47 PM

lee

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Joined: Jul 1999

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From: Lacey, WA

too rich

John,

If the truck has been sitting as you say a few years the carb probably needs a rebuild kit put in it. The gaskets dry out and also the fuel in the bowl goes bad and leaves residue behind. I would rebuild it and see if that cures your problem.

The black smoke could also be coming from the valve guide seals in the head. They may be brittle from sitting so long and allowing oil to seep past.

Good luck,

Jun 2, 2003 | 10:24 AM

millertime300

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From: Corvallis oregon

too rich

how long have you let it run for? I wouldn't be surprised if it cleared up on its own. Take the carb apart and soak it. That old varnish can make the floats stick down and all kinds of bad things, check the jets real close for any grit or grime.

P.S. it would have an opposite effect, but was the carb loose on the manifold? just wondering.

Jun 2, 2003 | 08:00 PM

john7979

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From: south jersey

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I rebuilt the carb and now it runs great turned out to be a bad power valve.

John

Jun 7, 2003 | 05:03 AM

quantalimo

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From: Florida

too rich

Wow Great to hear this .....John did the truck stop smoking after carburater rebuild...

Because my I6 is doing same exact thing yours was........

Ive never heard of a power valve in a carb..........

or was that in the head someone enlighten me here...

Last edited by quantalimo; Jun 7, 2003 at 05:07 AM.

Jun 7, 2003 | 07:16 AM

john7979

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From: south jersey

too rich

The power vavle or it might be called the accelarator pump is in the carb its a rubber diaphragm that tore and was allowing to much fuel into the engine. after I replaced that it stopped smoking and ran alot better.

John

Jun 7, 2003 | 12:09 PM

quantalimo

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From: Florida

too rich

Hey I went out today to the bone yard pulled a carb of a 79 f150 I6....Slaped in a POWER VALVE (Yes... Now I know what it is ""the Plunger"" LOL)

I got a carb kit from carquest for 15 bucks the carb itself for 23 at a u pull it junkyard ....38 bucks(for everything) im stylin........again...and I have a spare carb(unrebuilt)...

And wellah ooooooooo yes she purrs like a kitten now and she dont smoke......

Now I learned some new words lol..I knew the accelerator pump and what it was but never heard the term Power valve before......

Hey Thanks for the tips (This site and the people are a big help, thank god its all here)....

I was starting to think my piston rings or valves were going cause of the smoke ...

but now im very relieved....and Happy......