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Q-Jet Electric Choke Whoas - Any Gurus?

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by beefcake83, Oct 25, 2001.

  1. beefcake83

    beefcake83 1/2 ton status

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    I have a Q-Jet on my '94 crate motor. It has an electric choke on it, that i don't think is working like it should. When I start it up, the choke light doesn't light up. Then I have to hold the accelerator for a bit, sort of feathering it until a higher idle holds. Then, 20 minutes later, the thing is still running at high rpm, and will keep going until I finally go out and kick it down with the accelerator... and I have to do that harder than I think I should before it lowers down. I don't think my neighbors appreciate my loud beast at 5:30am (just got new performance exhaust done). Help! Any way of checking the choke, choke coil, etc. to see if things are okay? 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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    if its electric make sure its getting juice

    WHATS WRONG WITH A 305 ?
    81 K10 GOODYEAR 35" MTRS
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  3. Blazer_Boy

    Blazer_Boy 1/2 ton status

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    Choke unit is probably in need of replacement. Stick a voltage tester in the plug and have a buddy turn the key on and off. If its got juice and its plugged then your front butterflies should close shut when it gets juice. There's not to much involved in changing those.

    <a target="_blank" href=http://www.geocities.com/bigkern76>http://www.geocities.com/bigkern76</a>
     
  4. Grim-Reaper

    Grim-Reaper 3/4 ton status Author

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    Since it's factory electric the choke will not get power till the the engine starts. there is a pressure switch either behind the distributor or above the oil filter. When it's cold take the air cleaner top off so you can see the choke plate. This is BEFORE you touch the gas peddle to set the choke or start the engine. The choke (the flap on top of the carb over the front barrels) should be mostly open. Manualy give it full throttle once . The choke should set and that plate should close almost all the way. If it doesn't then take the rest of the air cleaner off and see how dirty it is. Hose it down with carb cleaner and make sure all the linkages on the passenger side are good and clean. See if the choke sets after cleaning. If it set then your probably good to go. If it doesn't set then either the bimetal spring has broke or the linkage is still jammed.
    First thing to do is make a mark on the dial and housing as a index mark so you know where to start. If the choke closed in the previous tests now is time to check that the Choke gets power when you start the truck. Test light into the wire on the side will confirm. No power then check the fuse with the test light by probeing the bare spots on the top of both legs of the fuse when the truck is in the run posisiton (doesn't need to be started.) lights on both side then it's good. Trace the wire from the choke back to the switch. With the key in the run possition check for power before and after the switch. If you have the electric mix control carb then you will have 3 wires on that switch. one goes to the mix control solonide on the top of the carb, one to the choke and one to the fuse box. If you got power on one wire then start the truck and verify you got power on the other(s). No power on the otherside then the switch is toast.
    If you have 12v at the choke with the engine running then time to check the element. If the choke opens then you may have a problem with the mix control solonide. If you follow the 2 wires on that one goes to the same switch as the choke and the other goes to a sensor on the water neck or the top of the intake. Unplug the wire from the solonide. Put your test light into the wire going to the senso. connect the other end to the + side of the battery. I don't remember if that goes to ground as it heats (light will be off or very dim) or it goes open as it heats (will be bright and go dim as it heats). But fire it up when it's cold and verify that it changes brigthenss as the engine warms. If it does then the mix control solonide has ate it causing a mixture problem in the carb.
    Ok back to the choke. You have already but an index mark on the choke. If you have a Ohm meeter you can unplug the wire and probe the terminal on the choke element and ground to the body of the carb. As I recall the choke should read about 70 ohm. If it read open or like 2-3 ohms then it's bad. I think the readings are correct. Been over a year since I tested one. Hopefully someone else remembers and can post it.
    If it read open then there may be some electrolisis where the element and the bowl meet and it's not pulling ground to function. Take the 3 screws out and very slowly pull the element out. pay close attention to how the hook on the bimetal spring engages the fork on the linkage (you will see what I mean). The hook on the bimetal spring will wrap around one of the forks. Inspect the backing plate for any corossion around the edge where it would touch the bowl. If there is some that may be your problem. If you got a Ohm meeter you can touch the backing plate (not the spring ) and the power side and again measure the the risistance and see if the element is good. Bad reading then you need to hit the parts store and buy a new one.
    When putting a new element on the tollerences are pretty good. What you want to do is look at the mark you put on the old one and install the new one at the same angle. Once it's on then manualy flip the linkage to open the choke. Manualy give the throttle one crank and see if the choke sets. If it did then your probably good to go and you can try to fire it up. If it didn't then rotate the dial till and re try till you get the choke plate to close. You will probably have to play with it a little to get it just right but the basics are the same.
    Good book to get is Rochester carb Tunning and modifying avalable at most parts stores, published by Haynes. Good book and will walk you through adjusting these carb.

    Women dig dents and flat paint!
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    Grim-Reaper
     
  5. beefcake83

    beefcake83 1/2 ton status

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    Hey thanks Grim! I was expecting a few one liners, but you delivered much more. I printed it out and tonight after work I'll have a look-see. I'll let ya know what it ended up being. Got typer's cramp? Thanks again for the reply!

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

    Grim-Reaper 3/4 ton status Author

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    [​IMG]

    Women dig dents and flat paint!
    <a target="_blank" href=http://communities.msn.com/OffroadK5s>communities.msn.com/OffroadK5s</a>
    75 Jimmy, Dollar
    Grim-Reaper
     
  7. beefcake83

    beefcake83 1/2 ton status

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    Re: Q-Jet Choke Whoas - Hey Grim...

    Hey Grim.... Can I probe your mind again? Well, did a little poking around tonight after work. Didn't get too much done in the dark and single digit cold, but found out a few things. I'll refer to the figure in my haynes book (pg. 4-35) in my descriptions. The other day when I posted the original subject, my carb was just being a pain... well today it crapped out about a minute after I started it up. It did the same thing in the past, and it turned out that the wire came off the Idle speed solenoid (6). Well not this time. Here's what happened today...
    I went to start her up like I normally do. Got in, pumped the pedal a few times, and started it. I held the accelerator down a bit for about 20 seconds to get the high-idle to catch. Only this time when I let off, the idle dropped down to almost dying instead of staying steady. So, I manually raised the idle back up and then it started running rough, dark smoke began to come out and it died.
    So, that brings us to tonight's check... I removed the air cleaner lid and checked the choke plate... it was closed shut... not open. I had the wife get in a turn the key to 'run' and press the throttle once. No movement in the plate... still closed. I removed the rest of the air cleaner and had her press the pedal some more to see how the linkages moved. They all seem okay. Connected and free-moving. The plunger on the idle speed solenoid (6) stayed still as the linkages that touch it moved away. (Don't know if that's normal). Anyway, I looked around, and can't seem to find anything out of the ordinary. I checked for power in the run position... first the fuse - good. Then the choke(21) - good. Then the idle speed solenoid wire - good. I MAY have found the pressure switch you mentioned. I found a switch right above the oil filter with three wires going into the tip of it. All three had power also. I couldn't go any further with the truck not running. I'll look some more tomorrow. Can you make sense of what I've written? Any other suggestions. Oh, on the choke light... does it come on after starting, or in the 'run' position? Does it go out on it's own before I kick down the high idle? Thanks! Gary

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

    Grim-Reaper 3/4 ton status Author

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    Re: Q-Jet Choke Whoas - Hey Grim...

    Well if there was power at the choke without the engine running then that switch is bad. That's not a big deal since it's sending the power verses no power. just don't put the truck into run and leave it with the engine off. The choke will cycle and it will give you start problems.
    Sounds to me like the choke element. As soon as the truck starts the plate should open a little to get air in. Since it's pouring black smoke out the pipes but not able to idle it sounds like it's drounding the engine in fuel.
    Sounds pretty close to what the Lady's truck did last time the Choke element burned out. If that doesn't fix it I would lay odds on the solonoide has gone south. Bring the old one with you to the parts store. They will probably have a Ohm meter that you could see what it reads and what a new one reads. If the read close to the same then its good. I think your going to find them way off.
    You can probably get the truck fired by jamming open the choke plate a 1/4 inch and get it to idle.

    Women dig dents and flat paint!
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  9. beefcake83

    beefcake83 1/2 ton status

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    Re: Q-Jet Choke Whoas - Hey Grim...

    I'll do some more checking today. The wife is saying ugly things like "for sale" and "outta here". Guess she's tiring of the constant $ spending on the beast. She says that my next vehicle will be in the 90's, and be fuel injected, be reliable and have good gas mileage. Probably a good idea up here, where you can die in your car in the winter if you break down. A newer vehicle is kinda fine by me, but I love my K5. Well, better go see if I can redeam my Jimmy from doom.

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

    beefcake83 1/2 ton status

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    Re: Q-Jet Choke Whoas - Hey Grim...

    When you mention 'the solenoid'... exactly which one are you refering to? There's an idle solenoid, and the mix control solenoid. Where exactly is the mix control solenoid found? I hate carbs! Thanks, Gary

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

    Grim-Reaper 3/4 ton status Author

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    Re: Q-Jet Choke Whoas - Hey Grim...

    Well I may be calling things wrong. Idle solonoide to me is the solonoide that kicks it up when the A/C is on. It is on the driver side front of the cabe and wired to the same wire as the clutch on the a/c most of the time.
    The mix solonoide is a 80's emmisions thing that other wise screwed up a great carb. It is controled by coolant temp and what it does is leans it down as the engine warms. On the top front passengerside of the carb will be a 2 wire plug if you got one.
    As for your wife thinking 90's is better. Point out if you put 6 months of car payments into your truck you would have little or no problems with it. Now I don't deal with the cold you got up there but I don't bat an eye at hopping in the Lady's 79 or my 75 and taking 200 mile trips in them. I've gone through them and fixed everything. They are in top notch condition and need almost no attention now. I have dragged my mother car home 250 miles. Just dragged my sisters furnature 250 miles. Only think I did was change the oil that was due.
    15-20 year old vehicle will have it's spells esspecialy if previous owners let things go. Once you get it back in shape and do the general maintance like it should have been done then you get a dependable vehicle.
    Also FI is nice but they have thier problems also. Trouble shooting one can sometimes be a game of trial an error or swapping parts till the problem goes away. I know if I ever had a fuel system problem on my truck that I ether need a $1.20 fuel filter or a $14 rebuild kit or $15. fuel pump and a hour and it will run. You can get any of those parts within any 2 parts stores on the planet. Worse case you can get a whole rebuilt carb at almost any parts store also and be running in 30 minutes. most of that stuff is cheap enough that you can afford to buy the parts and pack them in the truck for "Just in case" and fix the truck where it dies. You usualy can't do that with a FI vehicle. You have something like a fuel pump go thats a drop the tank job and fuelpumps diying is not uncommon on a 10 year old FI vehicle.
    I'd put a stock K5 against any new vehicle in bad weather driving any day. The only thing in its class as far as dealing with the rough stuff built in the last 10 years is stuff like F250's. Her justification of more reliable is going to set you back 20k or more. Think about what you could do to your K5 with $5k. No contest...nothing made in the 90's except the last of the K5's and subs are going to be any better.

    Women dig dents and flat paint!
    <a target="_blank" href=http://communities.msn.com/OffroadK5s>communities.msn.com/OffroadK5s</a>
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  12. beefcake83

    beefcake83 1/2 ton status

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    Re: Q-Jet Choke Whoas - Hey Grim...

    Well, today I went out and took another look at her. I tried first to do the screwdriver trick to open the choke plate up a bit. She cranked, but ran very poorly, so I shut it off. I started moving linkages, and worked the choke linkage and fast idle cam linkage. It sort of flips up one way and stays. I moved it back to where it originally was, and then back to it's other position. I then tried starting it again. It then sounded like it's normal cold self, just a bit rough. I set the air cleaner back on and as I hooked the hoses all back up, it smoothed out. I let it run at high idle for 20 minutes and then kicked it down and shut it off. Later this evening, I hauled the trash to the dump, and everything did fine. I guess the real test will be in the morning. Supposed to be down to -15 tonight, but I have it plugged in.
    Now, could my moving the linkages have set what the choke element should have done. Does it still seem like the element is the prob? I'm going to head to town and pick up an element and hopefully the pressure switch too. All depends on how it reacts tomorrow and of course any suggestions that you offer (grin). Thanks again for the help!

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

    beefcake83 1/2 ton status

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    Re: Q-Jet Choke Whoas - Hey Grim...

    Grim - I read the wife your view on old reliables, and she liked what you wrote, but doesn't think she can wait until I do a ground-up restro on it. She said she would not even try a 200 mile trip in my beast. Women.... she'll never get it.

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

    beefcake83 1/2 ton status

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    Re: Q-Jet Choke Whoas - Hey Grim...

    Grim - Yes, me again. Went out this morning (Sunday) and tried starting the beast. She started but ran slightly rough. I left it idling and went under the hood. I removed the air cleaner lid and manually opened the choke plate. The idle raised and smoothed out. So, now it's time to head to Schuck's and pick up an element and pressure switch. Hope it does the trick.

    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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