My falcon has recently been running nicely on gas, and runs rough on fuel. The other day the gas conked out though. It will fire up but choke out within a few seconds of starting, (i think right after the initial firing on petrol when it's swapping over to gas), i assume the issue must be isolated to the gas system as the car works on petrol(roughly admitted)? Does anyone have any advice in regards to what component of the LPG system or what they think the problem might be?

i have a 1996 ford xh falcon longreach ute
runs on gas and petrol
the solonoid cracked in the engine bay
we replaced it and now we cant seem to run it on gas
is there anything i have to do to get the car to run on gas?