Rcimp,
Is there a full moon somewhere! As you can probably see the forum is plugged up with fuel gauge problems, all of which I have commented on and none of which have been resolved. You did your homework well. At this point it looks like your fuel gauge is no good.
The internal ground for the gauge should be the case itself...no need for anything special other than no gobs of old paint or what not that might insulate it. The only thing I can think of is to take the sending unit out of the tank and verify its function with a ohmmeter (sp). If it works, that's one component off the list.
I have had patch cords/jumpers that didn't 'bite' well and confused the troubleshoot. Maybe yours have terminals on the ends and are connected securely. You have read the procedure for testing the gauge itself. I would take your supply of jumpers and, using the trucks battery, do a 'no guess' test on the meter. Be sure to bond the case somehow to the - side of the battery. Power it off the + side and use the - side or the grounded case as the sending unit connection.
It takes the gauge, sender, wires connecting them together and to ground for the system to read properly. Let us know what happens...I keep looking around for Allen Funt and his hidden camera.
Stuart
