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Connect electric choke

Discussion in '1973-1991 K5 Blazer | Truck | Suburban' started by ankarback, Aug 20, 2003.

  1. ankarback

    ankarback 1/2 ton status

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    I´ve just bought a Rochester Q-jet from a -84 Blazer. It has an electric choke which my old carb on my -76 doesn´t. I can´t move the choke from the old carb. beacause it´s not working.

    The new carb. has a red and black wire from the top of the carb and one connection from the choke.

    What new sensors do I need and how do I connect the choke?

    It´s a 350 engine from -76.

    Hope someone can help me with this.

    /Johan
     
  2. R72K5

    R72K5 Banned

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    what number is the carb ? look on the side on flat pad vertically and read off the code, 7 or 8 digit code such as 17055228, etc.

    one wire for GM electric choke you need to run from IGN source, you havce two such ports on your fuse panel, run wire from there, run 14 or 12 guage though.

    when its ocnnected and with key and dash warning lights and guages on but engine off you will hear ticking of the choke heating up, turn it back off then and start the truck, adjust as necessary when cold to an 1/8" closing gap

    the red and black wires dont sound right for a GM carb, there shoudl be no other wires ont he carb anywhere unless its an 80 or newer ESC or EST controlled carb
     
  3. dyeager535

    dyeager535 1 ton status Premium Member

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    Sounds like you've got the cold mixture control carb.

    I *think* without it hooked up, the carb should act like a normal Q-jet, but I'm not 100%. We covered this awhile back, but can non-members use the search feature?
     
  4. Mastiff

    Mastiff 1/2 ton status Premium Member

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    Technically, the choke wire should not come directly from a key switch source, but from a oil pressure switch. I'm not sure it really matters all that much, it just keeps the choke from heating up when the key is on but the engine not running (cranking, listening to the radio?).

    If you don't have an oil pressure switch already, it's probably not worth messing with, but I'm not totally sure about that.
     
  5. ankarback

    ankarback 1/2 ton status

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    Since my english isn´t good enough to explain this I post a picture instead :-)
    What´s the switch with two cables on top of the carb for?
    It was hooked up to a sensor on the -84 blazer´s thermostat housing.
    My truck has a oilpressuregauge but it´s not electrical.

    I did do a search but I couldn´t find anything.

    /Johan [​IMG]
     
  6. sled_dog

    sled_dog 1 ton status

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    your gauge isn't what controls the choke, there is a thing that looks like a knock sensor I believe that is an oil pressure switch and that works the choke. On my k5 I have the choke wired straight to a 12volt source so its never on cause I removed the oil pressure switch doing a motor swap. I am getting a new carb with a manual choke so I'm not worried about it come winter. That looks like the electronic QJet on my buddy's 88 Caprice 350, I didn't think 84 K5s would have come wiht those??? My 84 sure didn't.
     
  7. dyeager535

    dyeager535 1 ton status Premium Member

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    Yep, that was the cold mix control only carb, and they WERE available on the trucks in the 1980's. This is not a computer controlled carb, (as evidenced by lack of TPS on the drivers side front face) it only runs off the sensor in the thermostat housing.

    Something about a dual capacity accelerator pump or such. If you can wire it back in, I'd do so just to see if it works, or try it without the sensor and see if it runs ok, or get another carb.

    The way automakers design things though, if the temp sender fails (or missing in your case) it probably works like a "normal" q-jet.
     
  8. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    If that 84' came from california with all the smog crap than it is a computer controlled carburater. Many of them came on cars as stated above but were also put in trucks here in california.

    85K5 3/4ton,14b0ltFF,10bolt,9"lift,35"boggers,16.5x14welds, big horse 406SBC/700R4 /forums/images/graemlins/k5.gif /forums/images/graemlins/angryfire.gif
     
  9. dyeager535

    dyeager535 1 ton status Premium Member

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    From the picture it is obvious that it is not a computer controlled carb.
     
  10. rjfguitar

    rjfguitar 3/4 ton status GMOTM Winner

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    For some reason I can't view the picture. /forums/images/graemlins/frown.gif
     
  11. ankarback

    ankarback 1/2 ton status

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    It´s very hard to find Q-jets here in Sweden so I have to get this one to work. It´s rebuilt two years ago so it´s in a really good condition. Do you know what the sensor is called? Does it have anything to do with the choke or is it a separate thing that controll something else?
    It´s looks like it´s just to buy a new thermostat housing and a sensor to make it work.

    /Johan
     
  12. dyeager535

    dyeager535 1 ton status Premium Member

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    Don't know what the switch is called, but it's likely nothing more than just a temperature switch. Has nothing to do with the choke, but it *is* a cold engine emissions device.
     
  13. Rustheap

    Rustheap Registered Member

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    Hope this helps! This is from an article on 73-87.com, which is a great site with lots of info. Check out the garage section.

    To start this off, I just wanted to tell a little bit about the stock Q-jet that came on my truck. 1985/86 Q-jets in U.S. trucks have dual capacity accelerator pumps. When the engine is cold, more fuel is needed for transition from idle to part-throttle. When the engine is warm, less fuel is required. Dual capacity pump solenoid (plug on top right front of carb) is activated by coolant temperature sensor (sensor in thermostat housing). At 170 degrees pump solenoid energizes, dual capacity pump valve opens and pump capacity reduces by about one-half. /forums/images/graemlins/thumb.gif
     

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