its just the accelerator pump, common problem, just put a new one in it, you have two ways of replacing it... either on the truck(tricky and reaaaal fun) or rmeoved from the truck,( a little less tricky but still is fun if you have never been inside of a Q jet)
alot of carbs have this happen to them, its very common, i have a few new accelerator pumps around here if you want one and dont want ot have to pay for a whole rebuild kit in order to get one, but then you will probablyh need airhorn gasket anyways cuz if thge carb is original old and never been taken apart for a long time then the gasket will most likely tear on you. i have a ton of of these and other gaskets and parts all new and unused in my stash, but they made a zillion different ones over the years, all based on casting code on the carb, so..
i can help you if you want to replace the pump yourself by explaining to you how to do it, in detail, if you need, PM or email me
