Last night I had been running my TF of petrol. I flicked the button for LPG (the light was out) but it wouldn't change fuels. It is an electronic fuel system and I know its hard to guess what the problem might be, any help really welcome:)

Assume there was enough LPG in the tank?

Could be outta gas
Could be a blown fuse
Could be a dud gas fuel cut solenoid
Could be a free flow gas cut valve
Could be a pressure converter problem
Could be a petrol cut solenoid (causes it to flood and not run)
Could be a damaged gas supply line
Could be a lead has come off a solenoid

Could be you need to go to a gas tech and get him to look...:D