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85 chevy problem

Discussion in 'Chevy Trucks' started by Gmgbo, Oct 7, 2007.

  1. Gmgbo

    Gmgbo Senior Member
    Messages: 159

    I have an 85 gmc 3500 with a 350 4 barrel out of a 77 c10. When im driving it it cuts out and feels like the fuel filter is clogged. It has a new fuel pump and filter, I also blew the gas lines out at the tank so those arent clogged. Next step is take apart the carb, but i want to see if anyone else has an oponion before i do that.

  2. SnoFarmer

    SnoFarmer PlowSite Fanatic
    from N,E. MN
    Messages: 7,921

    Does it do this when it is cold or hot?
    or dosn't it matter?

    The coil came to mind.
  3. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    A fuel pressure test is the best place to start....Does it have an inline fuel filter that you changed? If so, are you also aware that the Q-Jets have an internal fuel filter? They are an often over looked item. Did you check all the rubber fuel lines for kinks or deterioration especially under the cab?
  4. streetsurfin'

    streetsurfin' Senior Member
    Messages: 770

    A tiny hole in a fuel line or hose, even if it does not leak gas out of it, can draw air and seem like it is starving for fuel. Look for rusty spots on metal lines or rotten/cracked rubber lines. I had this experience with an 85 Dodge. Until it got bad enough that it started leaking gas, I was perplexed why it would bog under hard acceleration.
  5. Gmgbo

    Gmgbo Senior Member
    Messages: 159

    Theres no inline filter, just the one in the carb, i also traced all the lines from the tank to the engine and they all look good and dry. It does the same thing warm or hot. It was only doing it once in a while but now everytime i drive i cant mkae it up hills or anything. The truck will rev up but once u put a load on it, it will bog.
  6. Bruce'sEx

    Bruce'sEx Senior Member
    Messages: 873

    Any chance up hill it's not pulling fuel from the tank?
  7. Detroitdan

    Detroitdan PlowSite.com Addict
    Messages: 1,937

    Bad diaphragm in the fuel pump? Or maybe accelerator pump bad? Did it sit for any long period of time? I've never had any luck with a carb that took too long a nap. Too many things get gummed up and stick. I never rebuilt them, was too easy to throw them away and drop a $200 Edelbrock 600 on there. Then shut the hood and forget about it.
    I'm still not convinced it is fuel and not coil related.

    REAPER 2000 Club Member
    from 60050
    Messages: 2,228

    Could have gunk in the tank. Depending where the pick-up lays inside the tank when you go up it may be blocking the screen enough to cut off flow.

    Does it do this on flat ground traveling at highway speeds or only up hill?

    Can you take off from a dead stop like at a dragstrip without it bogging?

    Have you checked the coil wire for cracks and arc'ing?

    Look for small black spots any where the coil wire touches and if the wire is not black itself look closely along it for small burn spots where it may be arc'ing.
  9. Gmgbo

    Gmgbo Senior Member
    Messages: 159

    When it first started it was doing it on uphills, now its all the time. Cant take off like a dragster either. I will check the coil tomorrow.
  10. REAPER

    REAPER 2000 Club Member
    from 60050
    Messages: 2,228

    Are you getting good back pressure?

    Check your Cat converter as well to see if it is plugged.

    I am basing this that you now it is getting enough fuel.
  11. B&B

    B&B PlowSite Fanatic
    Messages: 12,777

    Does the truck have duel tanks?
  12. Gmgbo

    Gmgbo Senior Member
    Messages: 159

    single tank, no cats on it to get clogged, i pulled the carb off yesterday, hopefully i will get to it today. I drove it around the parking lot and in low and 1st I floored it and there was just nothing there, it either bucked a little or there was nothing nothing there.

    Then i got into my 89 chevy to drive home and the tranny went:mad: