Probably not enough propane. In my experience, you need to empty the propane tank after each day of flying. I just unhook the line and leave it off until i go flying again. If it was the first start, that would be my guess. The propane turns from the liquid to gas and makes the engine hard to start on the first flight of the day. Another way around it is just leave the powermax hooked up and after it intially lights the propane and then doesn't seem to start the ramp, just ease on the trigger valve a couple times and you will hear the engine spool up on the propane and then switch to the Jet-A fuel ramp. Hope this helps.