Welcome to the forum, all the way from England. I am not an expert on your coach but I think that if your engine is fuel injected (and unless it has been replaced/modified, it probably is being 1995/6) your fuel pump and filter are in the fuel tank. I am not sure how much fuel is required as a minimum, but I would think it should start/run on the 4 gallons (18 litres) you put in the tank. Can you hear the fuel pump start running when trying to start? Since someone has modified the engine to run on propane maybe there is something wrong in the fuel conversion technology used that switches between fuel sources.
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