351w desperate for help

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May 3, 2005 | 07:01 PM

hartattack

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Joined: Dec 2003

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351w desperate for help

i have a 86 ford f250 351w 4 bbrl that needs help and i cant keep paying garage to guess and not work. the truck had but sitting all winter, started up but was running rough. i had a tune up done but it didnt change anything as truck was runing rough and backfiring still,. the timing was fine. the garage put in some antibackfire valves in the exhaust with no change, sputtering and no power, still backfires. they put in a a new alternator to provide power to the auto choke as they said it was dumping fuel down the carb and blowing out hte exhaust. here is the jest of it. the truck starts good, has an ok idle but as soon as you put in gear it stalls. when you finally get it moving with double pedaling it, it runs rough for a few minutes, as it gets hotter in sputters more and more and backfire reappers, gets louder and louder and eventually craps out. the plugs get fouled after 5 mins, when plugs replaced the truck has more horsepower and runs better but the process starts all over again. please help, i've poured tons of cash into to beast and seems like no one knows anything around here.
joel

May 3, 2005 | 08:58 PM

70T351W

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Joined: Mar 2005

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From: azle texas

I would almost bet after a period of sitting you have carbon deposits in your fuel system ( injectors or the carburetor needle & seat) that have hardened and is causing fuel to poor into your intake. It happened to my 351w, it sat for a year then one day I went to start it. It started fine and ran good at first but then it would flood out. The needle was not seating correctly due to build-up and sediment from the fuel. I put a carb. kit in it and that took care of that. Another thing you said about your plugs........if they are fouling out I promise you are getting to much fuel. when installing your carb kit be sure and recalibrate your floats to the carb kit specs. Tony

May 4, 2005 | 09:49 AM

Kemicalburns

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Joined: Jul 2002

Posts: 14,285

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From: Bend,OR

have you checked for vacum leaks possibly the carb isnt hooked up properly. what kinda carb is it. maybe your coil is bad not giving enough spark to the plugs. What is the timing set at. should be about 8-10*

May 4, 2005 | 09:59 AM

Momudder720

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Joined: Jan 2003

Posts: 1,162

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From: House Springs, MO

Definite carb issue. Change that sucker out and I can almost assure you that your problems will go away.
'But why didn't the shop do that?'
Because they wanted to hit you with the BIG bill first, then charge you a measly $200 bucks for a $20 carb kit.

May 5, 2005 | 01:04 AM

munrow

Senior User

Joined: Oct 2003

Posts: 188

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From: Miami, FL.

Sounds like the shop you went to was screwing you. WTF are "anti-backfire exhaust valves"?

May 5, 2005 | 07:25 AM

hartattack

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is a carb fit a rebuild kit? thye said the timing was fine, i jsut dont understand why when you replace the plugs it runs great for about 5 mins them the plug turn to crap again, sputters and starts backfiring all over again

May 5, 2005 | 07:56 AM

Kruse

Fleet Mechanic

Joined: Mar 2004

Posts: 1,529

Likes: 35

From: Kansas

Quote:

Originally Posted by hartattack

That carb is putting so much fuel down the intake manifold that the plugs are fouling from too much fuel. When you put some new plugs in, they work until they also get fuel fouled. While this is happening, your truck is belching out a lot of BLACK smoke, isn't it? As some other posters said, get that carb rebuilt.
You also will want a new fuel filter on your truck. The tank obviously picked up some sediment while it sat. The only other possible problem you have is bad fuel from sitting too long.
And get a new mechanic while you are at it.