Gas Gauge

[extremesounds13]

I did some searching and couldn't find an answer. The gas gauge in my seventy burb is always on empty and I want to fix it. I unplugged the brown wire that comes from the gauge and plugs into the fuse box and the gauge goes to about the three o'clock position. So my assumption was is they wire coming forward was grounded. So I went to the tank and as close as I could I cut the brown wire and then ran a new one up to the wire that was unplugged from the gauge and nothing changed it stayed a three o' clock. In fact even if I ground the wire going right to the gauge it stays at three o'clock too, but as soon as I plug it back in the fuse box it goes to empty. So what am I doing wrong? Is the brown wire not the right one going back to the tank. Or what else could it be?