Well here is the deal as best I can figure it out. The rf filter attached to the voltage regulator on the back of the panel came loose from the screw that holds it to the panel. It made contact with the positive stud to the ammeter. At the same time it was touching the circuit board. A part of the board is showing damage. Mainly the upper left corner. It seems the fuel gauge goes haywire only when the instrument lamps are on or the left turn signal. If I remove the dash bulb for the turn signal the fuel gauge is fine.

Anyone know where I could find a schematic to the circuit board on a non rallye dash car?