Well the onan 7500 quiet diesel is finally running. I finally broke down and took it to the Cummins onan shop here in Amarillo. After removal and inspection, we found that the injector pump had catastrophically failed. They said it was the first they had ever seen. $2000 dollars later its up and running.
Should you ever need service I would recommend these guys. As expected, not cheap, but courteous and helpful. Let me in the shop to look things over while it was torn down. Good learning experience and now I know what it looks like behind those panels. Quite simple actually.
Many thanks to all who posted trying to help. .