come to think of it after reading some of these other posts and remembering a situation i had not long ago, i had a genie rough terrain truck with a ford engine in it with a nolffs lpg control that did this very exact thing. All it turned out to be was the diagphram in the mixer was defective. It ran me around in circles for a day or so before i figured it out. Once i replaced the diaphram it ran fine.

just a thought to ponder...