The fuel terminal on the fuse box has a tan wire running from it to the no.. 4 terminal on the cluster plug next to the pink power wire for the gauges. The pink wire runs from the fuse box cluster fuse. to the no. 3 terminal on the plug.
With the key on if you disconnect the fuel terminal wire, the gauge should read at the 2:00 O'clock position. If you then ground the fuel terminal on the fuse box, the gauge should go to dead empty.