Furnace runs but will not ignite

our camper's furnace has performed flawlessly since '05 .... we are currently in Texas where it has been used many times .... I was very surprised a few days ago it didn't light .... standing beside the outside exhaust port I heard the fan cut on, got a faint whiff of propane, heard a spark and what sounded like a faint pop .... as noted after failing to light after 4 attempts it would cut off .... the majority of the working components in our furnace can be accessed by opening the outer cover and then moving a shield .... with the cover removed we tried it again and the same process followed .... believing it had to be a propane issue I tapped the heater's valve that controls the flow of propane several times .... turned it on again and this time it fired right up .... it has continued to work for the last 3 nights .... it appears the valve was stuck .... even though it is working, it will be replaced when we get back home

Jim