Gas guage with dual tanks

[mikedag]

Hello,
I recently acquired a 86 Chev with the dual tank system and I have a couple of questions/concerns.

The first being the fuel gauge. It seems to come and go. For example I'll start the truck and it will be on empty (tank is actually full), and if I start it again immediately after the gauge could read full and go to empty within minutes of driving. Switching tanks makes no difference. To my understanding this is a problem with the gauge because it is consistent with both tanks....am I correct? could it be a bad connection?

The second concern is when switching the solenoid over it sometimes makes no noise and other times makes a loud buzzing noise....Is this an indication that it is crapping out and I should be investing in a new one?

I don't know much about this system so I am looking to you gents for help,
Mike Dagenais