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Grim or anyone.... A Bit more carb help please

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by beefcake83, Dec 3, 2001.

  1. beefcake83

    beefcake83 1/2 ton status

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    Having a bit more trouble with the Quadra-Junk. I thought I would have to do a rebuild today cause it was really flooded out, but turned out to be that the choke was mis-adjusted. After properly adjusting it so the notch lined up with the one screw and cleaning out the spark plugs, it fired up.... with the help of something stuck in top to hold the choke plate open a bit. Can someone tell me what moves the plate to open it when cold? Once it started, and warmed up I could remove the 3/8" extension out of the thing and it ran and drove great. Shut it off and a few hours, went to try it, and had to prop open the plate again to start it. So, I need to find out what is supposed to open the plate, so I don't have to remove the air cleaner lid and prop it open each time. Thanks in advance.

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     
  2. K10ANDYKHAMNIC

    K10ANDYKHAMNIC 1/2 ton status

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    Re: Grim or anyone.... A Bit more carb help please *DELETED*

    Post deleted by K10ANDYKHAMNIC
     
  3. beefcake83

    beefcake83 1/2 ton status

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    Hey now... what's this... piggy-backing on my help request. The wife says to take yours back to the place that rebuilt it, and tell them to do a better job this time.

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     
  4. beefcake83

    beefcake83 1/2 ton status

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    Grim - In your past help you gave, you mentioned that before doing anything with the throttle, the plate should be mostly open, and then should almost shut when the choke is set. Well my plate is fully shut at first, and doesn't seem to open without help from an object used to prop it open. Any ideas??

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     
  5. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    With the motor dead cold...loosen all three screws holding the choke housing and rotate the housing counter clockwise until the choke plate just starts to open. Snug the screws up. Pump the gas once and start it up. It should fire up and be running on high idle. Watch the choke plate for a few minutes and it should slowly begin to open. After a few minutes snap the throttle to get it off the fast idle cam and continue to watch. If it starts to stumble and die the choke may be opening to fast (lean choke)

    Rotating the housing adjusts the time it takes for the bi-metal spring inside the housing to open the choke plate. The more it is rotated counter clockwise the faster the choke will open up. Rotate clockwise a bit to slow it down a little. It sounds like you have the choke set too rich...or too far clockwise.

    I live in a reasonably mild climate...so I run my choke a little on the 'fast' side. If I lived in a colder climate I'd want it slower. Commonly I re-adjust my choke for summer and for winter for optimum start-up and economy.

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
    <a target="_blank" href=http://coloradok5.com/gallery/project_T2> tRusty pics...</a>
     
  6. beefcake83

    beefcake83 1/2 ton status

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    Thanks TRusty - It's at -30 right now... brrr! I have the choke cover adjusted to what the book states it should be set to... the little notch is in line with the front top screw. So, you're saying I should adjust it more? I guess it's worth a try. I'm willing to try anything at this point. - G

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     
  7. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    For reference mine is set near to the middle of the two top screws...12 o'clock more or less. Well that's where it was until i re-adjusted it yesterday. Now it's more like 11 o'clock.

    Your choke is set too rich...try it at about 1 o'clock and see how it is. It may take a little trial and error to find the perfect spot. Just remember the closer you get it to 'perfect' the smaller your adjustments should be.

    Rene...-30 brrrrr[​IMG]

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
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  8. beefcake83

    beefcake83 1/2 ton status

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    Rene - The more I think about what you suggested, it makes more and more sense. I'll give that a try first thing in the a.m. and see what happens. How did you find this out? - Gary

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     
  9. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    I took apart a choke housing to see how it worked. All it is is a bi-metal spring that expands with heat (12 volts=heat) the spring is attached to the linkage and all rotating the housing does is delay how long it takes the spring to move the linkage. The spring expands and uncoils at the same rate no matter how it's adjusted. The housing just repositions the spring.[​IMG]

    Amazing the stuff you learn when you're too poor to pay someone to fix your car.[​IMG]

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
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  10. beefcake83

    beefcake83 1/2 ton status

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    Well, I know my bi-metal spring is good, cause I just replaced it 3 weeks ago. Guess I just need to get it in the right position now. Is it tomorrow yet?

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     
  11. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Tomorrow never comes...it's always today.

    Have fun with it! By the way, if it runs great now are ya still selling the old girl?[​IMG]

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
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  12. beefcake83

    beefcake83 1/2 ton status

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    I'm afraid so... Too many things I'd want to do to her, and the $ isn't growing on trees. Plus these little break-downs aren't helping with the reliability cause. Up here in this insane cold, on the side of the road is where you don't want to be. The wife keeps bringing up how much money I have dumped into my last 3 vehicles, and they all sold for less than paid for. She wants me to have something newer, and fuel injected... and something she won't be worried about driving. She's afraid she'll run over someone in the beast. And as much as I love the thing, it would be good to know that when I turn the key, my ride will fire up. I've had just too many Carb troubles.

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     
  13. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    Well good luck with it. Don't be a stranger once it sells either! You never know, you just might find yourself with another blazer one day...[​IMG]

    Rene

    <font color=green>Dyslexics of the world...UNTIE!</font color=green>
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  14. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Looks like Rene Has you covered. I agree with him...sounds like a misadjusted choke. When I replaced the element on the Lady's it took some playing with it to get it right. The bi-metal spring seems to settle the first couple weeks and they need to be adjusted again. With your extremes in temp your probably going to have to adjust it every spring and Fall.
    As for FI....ehhh it's nice but once you get that carb just right it will run good. The engine in the Lady's truck once it's had it's first run of the day you don't even need to set the choke. Just give the key a turn and it fires off first lick.

    Women dig dents and flat paint!
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    Grim-Reaper
     
  15. Blue85

    Blue85 Troll Premium Member

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    But there's still one thing that nobody has mentioned here that should be on an '83 Q-jet: rear vacuum break. There should be a little vacuum motor mounted on the passengers side on the back of the carb with a vacuum line running into a port at the top rear of the carb. The job of that thing is to prop the choke open just a little bit after the engine starts. It's tricky to get the whole warm up cycle to work right using the bi-metal spring alone. You actually want the choke plate virtually closed all the way during cranking, but then as soon as the engine starts, you need it slightly open. Then you want the plate to open slowly, but not be all the open before the engine is warm enough. That's the job of that little "vacuum break" (which is a misnomer, but it's name nonetheless).

    The bimettalic spring should hold the choke completely closed after you tap the throttle on a cold engine. That gets you super rich for starting. Then as soon as the engine fires, it creates some vacuum, which pulls the rear vacuum break and pulls the choke plate just a little bit open. It stays like this until the spring gets warm enough to start pulling the choke open further. Now if you give the engine a lot of gas, the vacuum signal is weakened and the engine is enriched more, which is important for a cold engine.

    So you might want to take a look at this little vacuum deal and see that the line and vacuum motor work and that the linkage is adjusted correctly to just hold the choke plate open after the engine starts. Then the bimetal spring can be adjusted so that it just holds the plate shut on the highest cam.

    <font color=green>Oh man, 4:10's are sure better than 3.08's!</font color=green>
     
  16. beefcake83

    beefcake83 1/2 ton status

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    Well, I'm about to give Rene's idea a shot. Got my fingers crossed that it'll solve this re-occuring choke headache. If not, then do I look at the vacuum break? And don't I need a vacuum pressure tester for that? Well, let's see what the choke adjustment does...

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     
  17. beefcake83

    beefcake83 1/2 ton status

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    Hey Rene - Well, I just battled the cold and did the adjustment you suggested. I rotated the choke around until the plate just started to move. I tightened there, and went and pressed the accelerator pedal once and turned on the key. I looked at the carb plate before trying to start it, and the plate was opened 1/4". All seemed well. But as I cranked it, nothing. Just cranks. I didn't want to touch the accelerator at all to not flood it out. Any suggestions? The Vacuum Break? - Gary

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     
  18. tRustyK5

    tRustyK5 Big meanie Staff Member Super Moderator GMOTM Winner Author

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    You went too far...turn it back a little.

    Rene

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  19. Blue85

    Blue85 Troll Premium Member

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    You don't need a vacuum tester, just plug and unplug the hose while the engine is running to make sure that it moves.

    <font color=green>Oh man, 4:10's are sure better than 3.08's!</font color=green>
     
  20. beefcake83

    beefcake83 1/2 ton status

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    Rene - Now this is getting weird.... I tried setting the cover where the plate just started moving... just cranks. Moved it a bit more... just cranks. Then I tried putting it back to where the little notch is lined up with the top front screw... nothing. I stuck an ink pen in the top to hold the plate open, tried it, and it acted like it was trying to fire up. ??? I'll keep trying different positions I guess. Maybe like you said, a bit under what I set it this morning. - Gary "The thing is just allergic to the cold"

    Gary Graham
    '83 GMC Jimmy w/ '94 350 'Beefcake'
    Eielson AFB, Alaska
    Metallica & Mountain Dew
    http://community.webshots.com/user/beefcake83
     

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