'99 Camaro fuel gauge pegged full

Hope this is the right spot, if not let me know.

1999 3.8L coupe with gas gauge pegged. Power off gauge is off/empty. Add power and gauge pegs out "full".

I ran across a great site where someone cuts thru to access the gauge/fuel pump assembly without having to drop the axle and tank but want to check electrically first before i get into that. Fairly handy with multimeters and troubleshooting but can't find reliable schematics / wire color codes / resistance measurements.

Occasionally when warming up in the morning gauge will "wander" slowly which I thought might be a bad ground, but my understanding is that the pump and gauge share the ground so I would expect fuel pressure problems but not so. Fuel feed is good so either the float or the gauge is bad. IIRC I did visually ID what appears to be only one grnd wire.

I have determined about 300mi. per tank but still a PITA to remember all the time.

Any good tips on checking this out so I don't have to cut thru to the tank or pull out the instr. cluster which doesn't sound all that fun . . . . and now that I think about it . . . I'm SURE it won't be?

Thanks

It would sound like the sending unit reference wire to the gauge is in fact grounded out.