Just checked and I still don't have any voltage reading in the red/green wire in the ignition switch.
Then replacing the fuel pump relay will not fix the problem.
You MUST have 12 volts on the red/green wire with the ignition switch in the Run position for any part of the fuel system, ignition system or computer system to work properly.
Accessing the ignition switch to test the voltages:
There are 2 other screws in the lower dash cover that need to be removed
The ignition switch is under the plastic cover on the steering column. There are 3 long screws that secure the top and bottom parts of the plastic cover. The screws are located in th bottom cover.
Using the diagram below, look for 12 volts on the red/green wire with the ignition switch in the Run position. Measure it right at the switch.
Diagram courtesy of Tmoss & Stang&2birds
Good 12 volts on the red/green wire at the switch with the ignition switch in the Run position, then the switch is good.
The problem is in the fuse link located in the wiring harness.
No 12 volts at the red/green wire at the switch with the ignition switch in the Run position, then check the yellow wires going to the switch.
Good 12 volts on the yellow wires, then replace the ignition switch.
No 12 volts on the yellow wires, then the fuse link shown in the diagram above is blown open.
See the following website for some help from Tmoss (diagram designer) & Stang&2Birds (website host) for help on 88-95 wiring
http://www.veryuseful.com/mustang/tech/engine/ Everyone should bookmark this site.
Ignition switch wiring
http://www.veryuseful.com/mustang/tech/engine/images/IgnitionSwitchWiring.gif
Fuel, alternator, A/C and ignition wiring
http://www.veryuseful.com/mustang/tech/engine/images/fuel-alt-links-ign-ac.gif
Complete computer, actuator & sensor wiring diagram for 88-91 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/88-91_5.0_EEC_Wiring_Diagram.gif
Complete computer, actuator & sensor wiring diagram for 91-93 Mass Air Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/91-93_5.0_EEC_Wiring_Diagram.gif
Vacuum diagram 89-93 Mustangs
http://www.veryuseful.com/mustang/tech/engine/images/mustangFoxFordVacuumDiagram.jpg
HVAC vacuum diagram
http://www.veryuseful.com/mustang/tech/engine/images/Mustang_AC_heat_vacuum_controls.gif
TFI module differences & pin out
http://www.veryuseful.com/mustang/tech/engine/images/TFI_5.0_comparison.gif
Fuse box layout
http://www.veryuseful.com/mustang/tech/engine/images/MustangFuseBox.gif
87-92 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang87-92 PowerWindowWiring.gif
93 power window wiring
http://www.veryuseful.com/mustang/tech/engine/images/mustang93PowerWindows.gif