I would second that - overfill. What's the rest of the story - where were you hogging away? My neighbor called because his Allis died hogging. I got there and he was on the ditch side with the tank outlet uphill and a quarter tank of diesel. Amazing, we poured diesel in it and it fired up.
Point being; if you were on a hill you may have sucked air with a bad seal in there. Over fill it and it should help. Oh, and pray that's it the whole time you are holding that 5 gallon bucket up there.