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Pesky Little Carb Problem

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Can Can, Nov 19, 2000.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Every winter I run into the same cold starting problem with my 84 305- I pump the gas once to engage the choke. I'll start the truck and she'll fire right up. After about 10 seconds at half-assed high idle, the engine will stall out with syptoms of rich mixture. I turn the key again right after she stalls, and the engine will fire right up to high idle with no problem at all. This happens EVERY morning, but I just learned to live with it. BTW, the truck runs perfectly other than this.

    What is causing this problem?
     
  2. k5kurt

    k5kurt Registered Member

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    Hi Canmore. My 83 was like that, and I diconnected the choke and ran a trottle cable instead. ran good then, but had to pump the sh-- out of it to start. Bought a new carb with ell. choke and haven't had any problem since.
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I actually have a relatively new carb, with an electric choke, and like I said, other than the first ten seconds of a cold start, she runs like a champ. There has to be some simple adjustment I can make to kick this gremlin out of my carb!!!!

    Where's Grim when you need him?
     
  4. DMK

    DMK 1/2 ton status

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    Check your fast idle speed and set to specs.
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    It's funny that you mention that......I was pretty sure that might have something to do with it, but after having it checked out, I was told by two different guys that it was perfect. On the second try it goes right to high idle with almost no hesitation at all.........but why not the first time?
     
  6. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Maybe you need to lean out the choke. If it is not opening quickly enough you'll get a rich condition very quickly. On your choke housing there should be either 3 little screws or 3 rivets [​IMG]. Obviously you would prefer to have screws for adjustment reasons. You need to rotate the choke housing one or two notches toward lean (choke opens faster). This should fix your rich stall on cold starts. If you have rivets on your choke housing, mark the position it is in now and then drill out the rivets. You can get new rivets from most parts stores, they usually have them in the rebuild kits as well. Then re-install the choke housing in the leaner position and re-rivet it.

    Rene

    [​IMG]
     
  7. Stoopalini

    Stoopalini 1/2 ton status

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  8. Blazer79

    Blazer79 1/2 ton status

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    What kind of carb do you have? If yours is like mine, (4MV) maybe one of the little vacuum canisters mounted on the sides of the carb could be bad. Especially the ones controlling the choke. The solution to your problem may vary depending on the choke type you have too. There are divorced-style, hot-air type, and electric. Tell us more and we might help more.

    <font color=blue>//////
    http://blazer79.coloradok5.com
    </font color=blue>[​IMG]
     
  9. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Thomas- The heat riser is in place and the thermovalve in the neck of the air cleaner works properly. I also suspected that something might be wrong in that department, but after a close inspection, I found that all my emission-related warm-up equipment was working well.

    Juan- I assume that I have the 4MV, but I know so little about the internals of carbs that I'm not sure what the vacuum canisters even look like. I do know that I have an electric choke, however.

    Anyhow, what really puzzles me is, after the initial stall, why does she fire up perfectly with no hint of trouble? Why is it that what happens in that first ten seconds is totally forgotten once I turn the key for the second time?
     
  10. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Maybe the choke plate is getting hung up. After it stalls and is re-started that is enough to unstick it.
    Try and start it cold without the aircleaner in place and just watch what happens as it dies.

    Rene

    [​IMG]
     
  11. 76chevy

    76chevy 1/2 ton status

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    You probably have a vacume leak at the base of your carb. Check and make shure that it is on tight. Sometimes the bolts can be tight and you can still have a leak. Spray some carb cleaner around the base and if it starts to die or acclerate you have a leak.

    <font color=red>Spirit of 76</font color=red>
     

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