Switch on electric choke

Discussion in 'Chevy Truck Forum' started by Boudin, Aug 8, 2011.

  1. Boudin

    Boudin Forum Moderator

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    Ok....I wanted to get some opinions on this as well as check and see if what I'm thinking about doing is smart or stupid.

    I have an edelbrock quadrajet model 1904 carb on my 84 c20. I have been getting around 11-12 mpg on trips entirely on the interstate. Recently, after I noticed that the electric choke wire had been disconnected from the fuse box for what I believe was an entire tank of gas on a trip entirely on the interstate....I got 14.5 mpg. It obviously didn't effect the performance enough for me to notice and since I got such an increase in gas mileage (20%).....I was thinking of adding a simple on/off switch for the electric choke. I don't have an ECM, so no issues there. It might have been a fluke, but I can't see what else could have caused such a sizable increase in gas mileage. If I were to install this switch, I am expecting to probably have to use it more in the colder weather....but once warm....I would be able to shut it off to save on fuel once warm.

    Am I way off base in trying this out? Does what I describe sound like that the "turning off" of the electric choke could have caused such a MPG increase? Opinions and thoughts are welcomed.
     
  2. chevychase

    chevychase Semi-Admin
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    Maybe choke is not opening all the way... check it after it gets to running temp.
    When you take power from it opening all the way. Maybe maybe not.
     
  3. Boudin

    Boudin Forum Moderator

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    Let me make sure I understand you. Are you saying I should run it until it gets to thermostat temp (180) and unplug the power to it? What would I look to see it doing? I would assume it would close like it wasn't even there.
     
  4. Case 7230

    Case 7230 Senior Member

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    I would fit a manual choke kit. You then always know exactly if the choke is on or off.
     
  5. chevychase

    chevychase Semi-Admin
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    If choke was closed all the way... you sure would not get better mpg,s.
    Would be gasping for air. Run like a 50 ford. lol
     
  6. Boudin

    Boudin Forum Moderator

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    That's exactly what I was thinking. Tell me this....the electric choke on this carb does what exactly when power is disconnected? Does it stay at the same position? If so, then the disconnect that I experienced was not the reason for the increased gas mileage....right? I just can't figure out what else could have caused a truck that has never broken the 13 barrier to get 14.5 all the sudden.
     
  7. repairman54

    repairman54 Senior Member

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    Electric choke has a heater that heats the bi-metal that opens the choke. Bi-metal is the "spring" that closes the choke. As the bi-metal heats up it loses it's spring tension and unwinds opening the choke.
    Before electric chokes they pulled heat from the manifold exaust crossover to heat the bi-metal to open the choke via vacum through the carb. or used a bi-metal in the manifold with a rod up to the choke linkage.
    With this hot summer underhood heat will eventially open the choke, it needs to be connected. I think your mpg increase is just due to the hot weather as hot air is less dense than cold air so less fuel is needed for the proper mix.
    Back in the day these auto chokes worked just fine as long as they were adjusted properly and were free and clean. All part of the carb. adjusting black art of the day.
     
  8. Boudin

    Boudin Forum Moderator

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    Thanks for the detailed description. Makes perfect sense. I actually had the hot air choke before I went to this edelbrock quadrajet carb. It was a touchy beast in the winter. I figured electric would be more reliable. The first winter with the electric choke is coming up....so really not sure if it actually reduces it's touchiness.
     

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