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Thread: 1986 Chevy Silverado - carb problems

  1. #1
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    1986 Chevy Silverado - carb problems

    I have an 86 Silverado with a 305. About a year ago, I was having problems whereby the truck would stall while driving and then not restart until some time later. This was after I replaced the fuel pump some months earlier as I recall. I took it in for repair and the shop send the carb out for a rebuild. It seemed to run better, but it still wasn't running right. It would still stall on occasion, but it would also jerk/stutter when it reached 45-50 mph or so, until you either let off the gas, or powered through.

    So, I finally took it to another garage a week or two ago, and they stated that they still thought it was a carb problem. So, they rebuilt it a second time (not sure if it's actually the carb I had rebuilt the first time, it could be that the first carb rebuild was a separate unit and they just kept the core). Unfortunately, it's still not working correctly according to the garage. They say sometimes it will run fine, but other times, it won't. It seems to alternate between running too rich, or starving for fuel.

    Now this garage is telling me that maybe the carb is just bad despite the rebuilds. Suggesting maybe I just need to buy a new carb.

    Now, I don't mind buying a new carb at this point, but I want to make sure that's the problem. What else could be contributing to this problem other than the carb? Would a faulty fuel pump or sending unit cause those types or problems.

    I'm completely naive to it as you can tell, so I don't want to shell out for a new carb and then not fix the problem.

    Suggestions? Also, if I do have to replace the carb, any suggestions on what type/model of carb I should look in to. Not looking for any high performance carb or anything, just something that will make the truck run right again.

  2. #2
    Senior Moderator chevychase's Avatar
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    Have not fooled with a carb for awhile . Seems maybe float sticking... getting gas .. then not .
    Or if it is a neoprene float maybe ... i think it water logged. When i did buy a carb i liked carter or eldebrock.Who is rebuilding it? Lot of younger mech. have no clue about a carb.
    Maybe someone else will jump on this.

  3. #3
    Senior Member onthethreshold's Avatar
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    If it's a q-jet and the builders don't know what they are doing your in trouble.Given the age of the truck it probaly needs throttle shafts rebushed,etc.there were alot of subtle changes in the q-jets from year to year and if you dont get the proper rebuild kit,etc.Could you possibly borrow a carb and make sure that is your problem and not a faulty fuel pump,vapor lock,etc?They also used two distinct needle and seat configurations that will not work ( they will fit but not be right)the welch plugs are notorious for leaking as well and there are variations on the accelerator pump (different heights and spring loads ) and if not set right they create problems.In short there a **** good carb if you know how to rebuild them proper.

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    Thanks guys.

    The guy who rebuilt it just recently is a mechanic who supposedly cut his teeth rebuilding carbs, so I had some confidence that he knew what he was doing, but who knows.

    The original rebuild, done a little over a year ago was done by a shop that specializes in carb rebuilds, so I would have hoped that would have worked.

    It would be a good idea to try to borrow a carb for testing, but I'm not sure I have access to one. I'll talk to the mechanic tomorrow and get a little more info on what he's done and what else he thinks might be the problem.

    Like I said, I'm not totally against shelling out a couple/three hundred bucks for a new Edelbrock or something, but I just want to make sure that's the problem.

    Thanks.

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    Quote Originally Posted by onthethreshold View Post
    If it's a q-jet and the builders don't know what they are doing your in trouble.Given the age of the truck it probaly needs throttle shafts rebushed,etc.there were alot of subtle changes in the q-jets from year to year and if you dont get the proper rebuild kit,etc.Could you possibly borrow a carb and make sure that is your problem and not a faulty fuel pump,vapor lock,etc?They also used two distinct needle and seat configurations that will not work ( they will fit but not be right)the welch plugs are notorious for leaking as well and there are variations on the accelerator pump (different heights and spring loads ) and if not set right they create problems.In short there a **** good carb if you know how to rebuild them proper.
    I just noticed you're located in Cuyahoga Falls. That's where I bought the truck in question. I drove out there a few years ago from Connecticut and bought it from Don Sitt's Auto. Drove it home to CT no problem, and it was good for a year or so, but then I've been having these problems since. Truck's in nice original shape except for that.

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    being an 1986 isn't that the carb that looks like a quad but is loaded with electronics?
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    Quote Originally Posted by leolkfrm View Post
    being an 1986 isn't that the carb that looks like a quad but is loaded with electronics?
    Not sure, I'm no expert but it looks like a pretty typical carb from what I can tell. It's a 4 bbl. I don't really recall too much electronic stuff around it, it looked pretty similar to the carb on a 1975 Pontiac I used to own.

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    does this truck have dual tanks? either way, it could be sucking air from the changeover valve or at the tank inlet. had a similar problem once. i ran a 3/8 rubber fuel hose from the tank to the fuel pump. that seemed to take care of the problem, so i replaced the rubber parts of the fuel supply line from the tank. when the truck quits check to see if the carb has gas in it by removing breather lid and pumping the accelerator. at least that will tell you if you have a fuel problem.

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    Quote Originally Posted by gpmorgan View Post
    does this truck have dual tanks? either way, it could be sucking air from the changeover valve or at the tank inlet. had a similar problem once. i ran a 3/8 rubber fuel hose from the tank to the fuel pump. that seemed to take care of the problem, so i replaced the rubber parts of the fuel supply line from the tank. when the truck quits check to see if the carb has gas in it by removing breather lid and pumping the accelerator. at least that will tell you if you have a fuel problem.
    Yes, it does have duel tanks. I was a little concerned when I mentioned that to the mechanic who's working on it and he replied he hadn't noticed. I've tried switching from one tank to the other to see if that makes any difference in the way it runs, but it doesn't seem to. Now, maybe that's because there's a problem in the changeover valve like you say, and it doesn't matter which tank it's pulling from. I'll mention that to the mechanic and see what he has to say.

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