How to Test a Choke Pull-Off

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Choke Pull-Off

Basic Purpose – When the engine is cold the choke valve is fully closed (some may have a small gap). This allows the engine to get that extra fuel it needs to get going. When the engine starts vacuum is applied to the choke pull-off which will retract, opening the choke valve slightly. How much, if any depends on the vehicle, but the bottom line is that the pull-off keeps the choke from closing too much when the vacuum drops down (engine speeds up).

Testing with a vacuum pump – Apply 15″ of vacuum to the vacuum line going to the choke pull-off. The pull-off should retract all the way and for at least 20-30 seconds. If the plunger isn’t retracted completely, replace the pull-off.

Testing with the engine running – Your engine should have at least 15″ of vacuum. This would be at idle. Again, if the plunger isn’t retracting all of the way, then replace the pull-off.

On a Quadrajet the choke pull-off has another job. At wide open throttle the pull-off controls the opening rate of the secondary air valves.

So if you are getting what seems to be a too rich condition when 1st starting your engine then the problem could be your choke pull-off, assuming your carburetor has one.

One Response

  1. I saw your video on the rochester 2g and I thank you for that. I have a 2gv (the divorced choke with seperate heat riser linkage and vacume relief on one side) and I am going to rebuild it. I was wondering if you could do a video on the 2gv which would include an explanation of the linkages setup and adjustment for the divorced choke and how that works with the choke plate and throttle body assembly on the other side of the carb and the idle screw cam settings. I bought an older car and the choke plate seems to be stuck in the open position no matter what? I have moved the manual choke linkages to see if I can get that choke plate to come down but something must have been done wrong as I cant get the initial startup condition/postion of the choke plate itself to be closed–and then it should open as the heat and vacume are applied to the linkage? I saw you had a 2gv on ebay but when i click on that link it will not display. Probably sold that carb by now. Any help would be appreciated.

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