Your poor fuel economy may be a clue. Dieseling is sometimes caused by fuel draining out of the carb after shutdown. When the engine is hot it doesn't need spark to ignite fuel that dribbled into the combustion chambers. Does the throttle plate close completely when you shut it down? Is the choke functioning correctly?


1955 First Series GMC 250 1-Ton Panel
In the Gallery
Mr. Hedgehog - Follow the build
If you can't laugh at yourself, I'll laugh at you.