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Choke setting?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by Dunc03, Feb 5, 2003.

  1. Dunc03

    Dunc03 1/2 ton status

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    My choke is opening extremely slow. I drove home tonight about 10-15 miles and the choke was still about half way closed, and it was still on high idle. IS there a way to adjust the choke so that it opens faster, or is electrically current the determinant of speed. I know the choke works off of the heat produced through electricity. The spring inside the choke heats and shrinks( or does it exspand) and opens the choke butterfly. Can I turn the choke to adjust the setting or does it just need more electrical current. Thansk for the help.
     
  2. BTCRAWFORD

    BTCRAWFORD Registered Member

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    Ive got an electric choked q-jet, to adjust it the engine must be cold. If the choke cover is rivetted on youll have to drill those out and get some appropriately sized screws to replace them. Using the indicator marks on the cover and the cast housing, slowly rotate the cover (backwards?) to open the choke plate a little at a time. We're talking about an 1/8" to 3/16" here, not much. Make sure you dab a little white paint or white out and make a pen mark to use as a point of reference for future adjustments. Living in Phoenix, I have 2 settings, Summer and Winter. Winter consists of about a month and a half of temps below 40, brrr! Summer starts about April and I have to open the choke up.
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Ok, heres how I'd attack it.

    Th choke(plate) MUST be 100% closed when the engine is cold and you hit the gas once. I hate assuming, but I'm betting your carb has a "choke pulloff" cannister. Once the engine fires, it will open the choke plate SLIGHTLY (we are talking a VERY small gap) to let a small amount of air in. (richens the mix)

    First thing first, make a reference mark on the choke housing and choke cover, so that when you rotate the cover, you know where you started, so you can go back to where it at least partially worked right. Don't pull the cover off, it's possible that could cause further problems.

    If it is taking too long to open, or not opening fully, you need to remove the rivets (use self tapping screws of the right diameter to replace them, or tap the holes, but make sure they aren't too big or the housing will break) and "loosen up" the coil. That means releasing tension from the internal coil.

    When you release tension on the coil, you also will likely prevent the choke plate from closing fully, which it should do of course. The cold spring is "tighter", so thats why the choke snaps shut when the engine is cold and the accelerator is pressed. If you play with the linkage, engine cold, you will see how to "reset" the choke so you can keep adjusting it without having to wait until the next morning.

    I'd "loosen" the choke coil up until it still pushes the plate closed fully when the accelerator is moved, but make sure that it is adjusted so the plate is only JUST closing. I hope that makes sense...instead of having excess spring pressure that would force the plate closed further if it was allowed more travel, after you adjust it, it wouldn't. You'll see what I mean if the coil is too loose...it won't close all the way, so you just keep "tightening" until it JUST closes fully.

    Anyway, if you can move the choke coil cover to loosen it (may be marked "lean" for the direction you need to turn it) quite a bit before the plate starts to open, then you have probably solved the problem. If it is already set so it JUST closes, you will need to STRAIGHTEN the rod that is screwed to the passenger side of the "choke shaft". You'll see it, it's usually green, and has a flat head screw holding a small bracket to the shaft. Pull that off and straighten (lengthen) it, small increments though.

    Beware, you start improperly changing the overall length of the linkage on a Q-jet, you will start having real problems. That should be your LAST method of adjustment.

    The choke coil heats up as it gets 12V (engine running, oil pressure present) and that RELAXES the bimetallic spring in there. The less "relaxing" the spring has to do, the faster it will open the choke. If the rod is adjusted incorrectly, (too long) the choke may still relax the spring quickly, but not have enough "travel" to open the choke plate fully, which is vertical.

    So you see why the rod is important, but if the coil is too tight, it may APPEAR that lengthening the rod is the correct approach, while it may solve nothing, and make the problem worse, or at best, just different.
     
  4. R72K5

    R72K5 Banned

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    when engien is 100% cold i always set my choke to be shut except about 1/8" gap, i ue a 1/8" drill bit to make the gap and make sure you have full current to the choke and that the choke is not old and worn out(spring steel weak)
    if you think you may not have full current then go to fuse panel and run a spade connector off an ignition unfused port on it and use inline 20 amp fuse and run it to the BATT terminal on cap using the factory wire eng and plug, use same guage wire its 12 guage i guess, something like that, this is how to convert to HEI on 74-down vehicles

    good luck
     
  5. dyeager535

    dyeager535 1 ton status Premium Member

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    </font><blockquote><font class="small">In reply to:</font><hr />
    when engine is 100% cold i always set my choke to be shut except about 1/8" gap

    [/ QUOTE ]

    thats what the pulloff does for you if your carb has one /forums/images/graemlins/smile.gif
     
  6. Dunc03

    Dunc03 1/2 ton status

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    IF the pull off canister is something with a vacuum hose running to it, then yes I do have one. On mine it sits right behind the choke and has a hose that runs to the bottom of the carb. I'm pretty sure this is the vacuum canister your talking about. The choke is fully closed, metal to metal, when it is cold. I have alreadyt had the choke housing apart once because the high idle was sticking. I had to take the cover off to loosen the housing screw so that the high idle arm would fall with the choke arm. When I reinstalled the choke I put it back exactly the way it was before. I also noticed that when I was rotating back to its original position that the choke closed fully before the marks for the choke lined up like they had previosly. In other words the choke closed and then I felt the spring tighten because I still had to move it more to get it back where it was. Your saying that I need to rotate the choke cover until there is no tension on the spring and the choke is fully closed. If this doesn't make it open fast enough then I have to bend the choke rod a little to get it right. About how long should it take for the choke to go off when it is working properly. It's been so long since I started this thing up that I don't really remember. Thanks for all the help
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    If you watch the operation of that "pulloff" it should be fully "retracted" with the engine running, and relaxed when the engine is off. Moving the choke blade itself will move that linkage if its the right one. (carb can have 2, 1, or no pulloffs)

    Sounds like you understand what I was trying to say /forums/images/graemlins/smile.gif

    The "fast idle" period is typically from 2-5 minutes, depending on application. (yes, my dad actually timed a few different ones at one point) Personally, my truck will run FINE after about 1 minute of fast idle, but GM of course set them to meet emissions standards as best they could, which could mean a longer fast idle period. Set it to open as fast as possible (as long as the engine tolerates it) IMO.
     

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