To run the truck on propane, you have to shut off the motor, switch to propane and then restart the motor. What would happen is you would shut off the truck, switch to propane, and the truck would not start. You would then switch back to gas and the truck still would not start. At this point, your truck was put on a lowbed and hauled to a dealer in Sacramento. You might see your truck again in a month! Our mechanics told me a valve under the hood was often the culprit, to the tune of over $2500! These valves would also leak propane under the hood...not a good situation. In all fairness to Ford, the little bit I ran the propane system the truck ran great, although you had to crank the motor approx. 3 times as long to start!