I was driving my 56 3100 the other day for about 15 minutes and the truck just died. It has it's original 235 6 cylinder engine. I sat on the side of the road and tried to start it. Would not start. I pulled the choke all the way out and it started. When I pushed the choke in it died. Managed to get home with the choke pulled out. Took the carb off and took the top cover off. To my amazement the power piston was jammed in its cylinder. I loosened it up and pulled it out, sanded it with fine sandpaper and cleaned out the cylinder and fine sanded it as well. Made sure it moved freely and reinstalled the cover. Started the engine and it ran great again. So if this helps someone with the same problem that will be great.