Alright I finally registered. Just bought my second bonneville last month, 99 SE, still have my 88 LE as well (though it had been stolen and the steering column is jacked up) and I have read quite a bit through the various gas gauge problem threads. Not sure cause mine isn't 'going to full' from empty, but specifically after I filled it up I parked with engine on for a while as I was writing out some checks and the check gauges ding sounded for...no gas. Gauge at empty. drove forward, it shot back up to where it should be, full. Through a procession of this, I found that if I parked and idled, it would go to empty eventually (I do mean in a minute or so) and would return to full if I moved it. Haven't driven any reasonable distance or so in it since fill up yet. This doesn't seem to match up to the other gas gauge threads i've seen exactly, but I am sure someone knows what it is. Thanks.

The guage in my old 99 SE started behaving like that too. Then, after 10,000 miles or so, it finally died.

Your sending unit is faulty. Very common failure on these cars.

So if and when this becomes a serious issue, does the 99 SE have the do-it-yourself fix for the sender like demonstrated (where the wiper piece is replaced) or is this a 600 dollar repair? Note I draw the line at dropping gas tanks myself, I'm acceptable at most things but I really don't have anyplace to do that anyway.

FWIW, unless the thing just rots apart inside the tank, the sending unit is completely repairable. You can fabricate a sweeper if that wears out, although I have never seen one wear out (300K on some cars I've fixed) Even the wire winding can be replaced, just need the proper resistor wire available at any electronics store that carries these kinds of things (not radio shack) Electronics geeks make their own wire-wound power resistors all the time, and that'* all this thing is really... a wire wound resistor.
Also, if the steel lines rust away at the top of the tank, you can buy bulk length tubing, bend it, flare it, (swedge it) - they make the proper tool for putting the correct swedge to fit our GM connectors - and then braize the new pipes in. This is time consuming, but for the cost of your first sender you can get the tools and supplies needed, break even on the first one - then the rest is gravy. Look around your hometowns, you'll find guys selling "rebuilt" units, just add a fuel pump - that'* what these guys are doing, and they're making 100 bucks a sender, doing about 4 a day while crushing beers by the woodstove in the garage after the kids go to bed. This sure beats watching American Idol. There are two guys within a decent driving distance of me, and they offer two prices, one where you keep your old one, one where you give him the old one. Sure, in about 10 minutes to 1 hour, he has yours turned around, on the shelf, ready to go with a price tag of about half the cost of a new one. Just something to think about, with all of you folks here with the same cars and the same issues. Charge the general public 100 bucks a rebuild, charge fellow BCers 50 bucks, everyone wins. Just my 2cents. Mike

Is this the problem caused by some gasolines that came through with a higher sulfur content. I noticed my Techron fuel system cleaned talks about how it protects the sensitive fuel level sending unit from damage from sulfur in fuels.

I wonder if putting in a dose might help clean the resistance wires and start the fuel gauge sender working.