Hi,
First - if you have the owner manual, it may show you which relay is where. If not, look on the underside of the cover you pull up to see the relays - mine has a label showing which relay is for which circuit. I have a 1994 explorer - same basic body style as yours. On mine, the A/C relay is right in back of the Fuel Pump relay. They are the last two relays in the back right side of the relay box with the A/C relay being the one in the back behind the Fuel Pump Relay.
If you want to be sure of which relay is the right one - turn the ignition to ON and turn on the AC. Even with the engine off, the AC pump clutch will be engaged and you'll hear the loud click as it engages. Now pull the relay directly behind the fuel pump relay (if you still aren't sure which one it is - start at the back right corner and pull that relay (it's probably the A/C relay). If you pull the correct one, you'll hear a loud click as the AC pump clutch disengages. Now, pull the relay right in front of the one you just pulled out - compare the pins to be sure they have the same pins in the same positions and see if you can find the part number on the relays and compare them to each other (Mark the A/C relay - it's easy to forget which is which) and then TURN OFF THE IGNITION NOW, then plug the A/C relay into the place where the Fuel Pump Relay goes. Leave the passenger door open - make sure it's quiet around you as much as possible and turn the key to on (not start). You should hear a noise that sounds like a quiet buzzer and it only lasts a few seconds. If you hear it - try to start the truck. If it starts - go to the local parts store and buy a new Fuel Pump Relay. For some reason, these are a common failure issue - maybe because they are on the entire time the truck runs - but in any case, put the new one in where the Fuel Pump Relay was - and put the A/C relay back where it was.
If the relay doesn't fix your problem. you either have a bad computer the expensive one), bad wiring/connections or a failed fuel pump. If you went over a hard bump when this happened or you had a passenger in the passenger seat - you should check the fuel safety switch to make sure it didn't trip. To get to it, pull the carpet down to expose the metal floor pan - it's located about 18" down right next to the hump under the carpet. it has a two wire connection going to it. If it's tripped, your fuel pump won't run. You push a button on it in to reset it. It normally takes a hard bump or a passenger that thinks they have a brake pedal and don't like your driving in order to trip it - but it's happened to others before so look there.
You can also get a tester at the parts store and it will help narrow down why you don't have fuel pressure. It won't tell you exactly what is wrong, but it will help. If you get one, make sure you get one made for your year of Ford and read the first few pages of the manual so you can tell what the blinking light means and how to use the device.
My guess (and this is only a guess) is your fuel pump failed. Don't change it based on my guess - it's expensive and you could have a bad relay. The relays fail more often than the pumps do.
Anyone else have input or corrections to what I wrote?
Ok at one point i read you could swap the fuel pump relay with the A/C relay as they were both the same part 
