I replaced the fuel pump on my 1999 4.0 OHV today. I'll do my best to provide a little background on the issue.
The integrated check valve had gone bad on my fuel pump causing my truck to loose fuel pressure while the truck was off. This forced me to constantly turn the truck to "Key on" then "off" several times to prime the fuel system, then I was able to start. If I didn't use this little trick the truck would crank for a 6-7 seconds before it would struggle to life.
I priced fuel pumps from Ford, o Reilly's, Advance Auto, and Autozone. The complete units were very expensive. I was quoted between $230 and $375 for the entire unit (Float Level, Pump, wiring). Auto Zone was the only one that had just a pump. I ordered a standalone AirTex fuel pump and AirTex strainer for just under $110 out the door.
I did my research on this prior to performing the repair and people stated that removing the bed was the easiest way. I agree 100%. It's so easy to remove the bed and after doing this from the top side, I can't even begin to imagine the frustration you would face while dropping the tank.
Remove the tailgate. Unbolt the two Torx-T45 bolts from the tailgate support and remote the tailgate.
Unhook the tail lights from the wiring harness. Crawl under the truck and look under the rear bumper.
Remove the bed. If you have a bed liner you'll have to remove it first. Make sure to unhook the 3 6mm bolts that secure the fuel filler neck.
There are 6 bolts that secure the body to the frame. The bolts have a Torx T-55 bolt head. I soaked these bolts in PB Blaster 1 day before removal and I believe this helped. The 1/2" impact made short work of this.
Tip: Don't expect your wife to be able to easily lift one side of the bed. My truck is body lifted so it made it harder for short people.
Disconnect the battery.
Disconnect the 1/4" and 3/4" fuel lines. You will need the special ford "spring lock"
Disconnect the fuel pump from the wiring harness.
Unscrew the retaining ring from the fuel tank. I used a steel punch and a 3lb hammer. I was very careful not to create any sparks. This slowly allowed the ring to come loose.
Carefully remove the fuel pump and fuel level sensor.
There is one retaining clip that is screwed down that secures the pump in place. The screw that hold this down also secures the end of the return line. Remove this screw and remove the retaining clip.
Remove the one hose connected to the fuel pump, and remove the electrical connection from the wiring harness. The fuel pump is now free.
Step 11: Graft the new pump in place of the old and reassemble in reverse order.
I know the pics aren't the best but I hope they help. I wish I had them when I was doing mine.