GM-GMC: gmc 305 cid hot air choke problem?, dieseling, metal coil

Question
Harry,
First off this carb problem.  I have a 84 gmc 305 cid with the rochester 4bbl carb.  The truck starts well and has a decent idol.  When you start out the truck doesn't seem to want to take any gas. If you try to give it any gas it will flood out and cut off.  I have looked at the top of the carb with the breather cover off when this problem occurs and the hot air choke is not opening fully when the truck should be plenty warm enough to disengage the choke.  I can manually tie the choke open and the truck runs fine.  Is this problem the choke and if so is there something I can do to remedy the one on it or can it be replaced without replacing the carb.  Sometimes it will open up and run fine.  Also, the truck will start dieseling upon shutoff and you have to turn the key back on, flood the carb, and turn it back off to get the motor to stop running.  I guess I want to make sure all the problems i'm having really are the carb and could not be related to something else.  I'm not at all above changing this problem carb if you think this is what it is and probably wouldn't be anything else.  I have had this truck looked at recently and the timing was supposed set at this time.  The plugs and wire have also just been changed as well as the rotor button and cap.
Mike

Answer
On a 20 year old, carbureted, engine any kind of problem is possible!

It sounds as if your choke spring (a metal coil that is either down in a little "well" on the passenger side of the intake manifold or coiled up in a housing on the passenger side of the carburetor) may not be working correctly, along with vacuum operated choke pull-off(s) that have stopped working or are out of adjustment.

Your dieseling problem is also likely to be internal leakage in the carb or an improperly set idle speed solenoid.

You can try replacing these parts, but the best solution may be to find and install a rebuilt carb.  Just before GM and other companies switched to fuel injection, carburetors became quite sophisticated and very hard to work on.