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I have to PRIME the carb to start...????

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Can Can, Jan 9, 2002.

  1. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Here's the scoop-

    My 84 has had a little gremlin in the carb for about 5 years. Every time I start her when the engine is cold, the motor will catch, jump to high idle, and then stall after about ten seconds. One more turn of the key without touching the pedal and she'll catch and stay running. Up until yesterday, this hasn't caused me any worry.

    HOWEVER, the last two days have left me scratching my head. After it stalls the first time, the only way to get the engine to run is to prime the carb with a bit of gas after it stalls the first time. Once started, the engine runs like a champ.

    SOOOOOOO.......what's the problem? I'm under the impression the choke isn't working properly. Rene and I talked about a potential problem with the choke spring, but I never got a chance to get under the hood today.

    Does anybody have any other ideas?



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  2. jimmyjack

    jimmyjack 1/2 ton status

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    Kinda far fetched but maybe your accelorator pump? Maybe a prob with your fuel pump? Dunno what you are running(not that matters) I was thinking like a vapor lock kind of a thing.

    That jeep thing? Yah I understand it....... Like my Blazer? <a target="_blank" href=http://community.webshots.com/user/blazerk5>http://community.webshots.com/user/blazerk5</a>
    Jim
     
  3. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    That's why I'm kinda confused. I run an aftermarket electric fuel pump, and I know I'm getting gas because once the motor starts after I prime her it runs great- no stuttering or bogging. In fact, last night when it first happened my wife drove 60 miles on the highway to get home. The truck ran great with no performance issues. This morning though, it did the same stall and not start trick.

    I also replaced both fuel filters less than 3 months ago. I agree it sounds similar to a vapor lock but that doesn't make sense, does it?[​IMG]



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  4. m j

    m j 1/2 ton status

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    to set the choke and start properly you depress and release the pedal slowly. then turn the key. should fire and run at fast idle until you kick it down.
    if you dont depress the pedal the choke isnt set

    formerly 77chev
    still a jerk though
     
  5. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    UMMMMMMMMM........yep, I knew that[​IMG]. I didn't think I had to add that piece of info.



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  6. m j

    m j 1/2 ton status

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    stock quadrabog?
    does it leak the bowls dry and fuel pump needs a sec to fill them?
    run the pump for a few secs before kickin it over
    tomorrow morning, if the bowls are slow leaking that would fill them and it would not do it.
    if it still does it then ???

    formerly 77chev
    still a jerk though
     
  7. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    I'm far from a carb king, but I think I know what you're getting at.....What would cause the bowls to leak back? Bad needle and seat?



    <font color=blue> NEVER FORGET, NEVER FORGIVE, NEVER SURRENDER<font color=blue>
     
  8. m j

    m j 1/2 ton status

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    grasping at straws here.
    heard on this site that a quadrajet carb can develop leaks and others fill some plugs with JB Weld
    the fuel line realy has nothing to stop it from gravity draining back to the tank
    the stumble sounds like a fuel problem so if I were you I would chase that down frst

    formerly 77chev
    still a jerk though
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I remember the fuel leak back thing from somewhere as well. Don't they have to epoxy something or other? Damn that sounds like real technical advice...[​IMG]
    Seeing as it first happened to your wife I'd recomend the new Edelbrock multiport EFI set-up...just tell your wife that her safety and piece of mind is very important to you[​IMG]

    BTW...wb Paulie![​IMG]

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
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  10. vince13

    vince13 1/2 ton status

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    sounds like you are having the same problem i did. turns out in my case that the float bowls themselves were actually cracked and overnight the fuel was just draining into the manifold. i replaced the carb and works fine now. but if that is the case then you will have to replace your carb cause that is a unfixable problem. thats just my 2 cents anyways. hope it helps

    73 Blazer 1Ton 6inch lift, 3 inch body, 36 inch swampers
    79 3/4 ton suburban, soon to be 6 inch lift, 3 inch body, and 44 in boggers. Oh ya
     
  11. Can Can

    Can Can Pusher Man Staff Member Super Moderator

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    Don't worry, Rene. I already spent about 1/2 hour sharing my limited knowledge of carburetors with my wife, and we both came to the conclusion that EFI would be a great idea if and when we have the extra cash. Maybe when the ol' 305 kicks the bucket I'll consider the upgrade. And thanks for all your help, brother- I really appreciate it!!![​IMG]

    Vince - Someone else offered me the same opinion. I think I may have to take the truck to the local shop and get them to diagnose it. What you're saying makes sense.......



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  12. dyeager535

    dyeager535 1 ton status Premium Member

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    If you have an electric pump, and *if* the float is working correctly (not binding) then as long as you let the pump "fill up" the bowls before attempting to start, (just wait 5-10 seconds then try cranking) whether they leak or not is a non-issue.

    FWIW, the well plugs tend to leak. They are plugs GM pushed into casting "voids", then peened the cast material around them. No sealer used, so thats why most Q-jets that haven't had the well plugs epooxied, will need to be cranked over for a few seconds before starting, if the vehiclke hasn't been started in a few days. The plugs let the fuel leak out of the float bowl, and into the intake.

    I've had vacuum leaks, that was a start an an immediate stall, then another start, and it would run, but idle was never smooth.

    Sounds to me like you have a choke problem. If your idle RPM's aren't high enough when the choke is set, the engine will stumble and die. If the choke blade doesn't open partially when the engine first starts, it will die. if the choke blade opens up too fast, the engine will stumble and die as well. So, if it were I with this problem, I would make sure that my "high idle" is above 1500RPM (2000 typically), and I would check that the choke isn't opening too fast, or too far too soon.

    After the truck dies, check to see what position the choke is in. It should definitely not be open very far after 10 seconds.

    Always pump the gas once before starting, you HAVE to do this to set the choke on a cold Q-jet.

    Dorian
    My tech/links page: <a target="_blank" href=http://www.dorianyeager.com/index2.html>www.dorianyeager.com/index2.html</a>
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