He took out the fuel tank selectoselectch, and it had obvious signs of heat...melted a hole in the side of it. Replaced it with one from my old junk 91 diesel. Now both tanks work, although the fuel gage doesn't, on either tank. It also now pumps fuel from back tank to the front one. I have another friend who is mechanically inclined, and he explained what is likely causing THAT, issue...but for now, I'll just run the front tank and hopefully someone will figure out why the fuel gage doesn't work, anymore.
I do want to thank all of you that offered advice.