Hi Mark,
I've got an '87 T-bird turbo coupe and this is quoted from my '87 ford factory shop manual (Chassis & Electrical volume B). Hope this helps.....
TEST TG CO DISPLAYED, ANALOG FUEL GAUGE CAN NOT BE CALLED UP
-------------------------------------------------------------------- TEST STEP RESULT ->ACTION TO TAKE
-------------------------------------------------------------------- TG0 VERIFY CONDITION CO displayed ->GO to TG1.
-------------------------------------------------------------------- TG1 CHECK FUEL SENDER WIRING AT SENDER
+Disconnect groud cable to battery.
+Lower fuel tank to gain access to fuel sender connector.
+Unplug fuel sender connector.
+Jumper variable resistance terminal and ground terminal of harness together.
+Reconnect battery.
+Tun ignition key from OFF to RUN.
+Check digital fuel display for CO or CS. Note: it may take several minutes for the gauge to respond.
CO displayed ->GO to TG3.
CS displayed ->GO to TG2. REMOVE jumper.
--------------------------------------------------------------------- TG2 CHECK SENDER
+Turn ignition key to OFF.
+Measure the resistance of the fuel sender at the sender terminals.
+Verify that the resistance is between 9 and 161 ohms.
OK ->INSPECT fuel sender wiring connector female terminals for flash or loose fit. SERVICE as required.
NOT OK ->REPLACE sender.
-------------------------------------------------------------------- TG3 CHECK FUEL SENDER WIRING AT CLUSTER
+Disconnect ground cable to battery.
+Remove cluster and secure connectors from shorting.
+Jumper variable resistance terminal and ground terminal of harness together at sender.
+Verify continuity between Pins 12A and 13A of cluster connector.
OK ->REPLACE tach/ multigauge module.
NOT OK ->SERVICE fuel sender wiring for open circuit.
--------------------------------------------------------------------
Bill