The fuel gauge is'nt working.I tryed to ground it

If your gauge reads full, the wire to the tank unit is grounded. Remove the wire from gauge to tank. The gauge should now read 'empty'. If still reading full, the gauge is faulty, or possibly it's the voltage regulator that supplies reduced voltage to operate the panel instruments. If the voltage at the panel unit is ok, run a makeshift wire along the outside of the vehicle to the tank unit. If it still read full, replace the gauge.

When testing a fuel guage you should disconnect the wires to it,guage should read over full,ground the float wire,turn off key then turn back on should read empty.You have to cycle the key for guage to move.If still inop the wire is broken in the harness between the tank and the dash.Voltage on the float wire is low.When tested with a test light it will barely light the light and pulsate.This test indicates the wiring is good.