Did you pull the wire plug off the top of the rear tank and check for volts there? follow that wire along the frame rail, i bet its been accedently cut or something. I think each tank has its own ground as well... if it hasnt been used for awhile the float may be stuck or gummed up as well - might hafta drop the rear tank .....

Just re-read your post - both tanks dont show level .... might be your gauge as montana said - id follow the wires along frame first ....