ok, so entering week six of the most frustrating vehicle problem i've ever experienced. 87 f150 4.9 300 straight 6. dual center tank. i remove the plug to the fuel pump at the tank and i have continuity across all 4 pins. i have checked all plugs that i've found and traced all wires and found nothing wrong. when i turn the key the relay kicks on but nothing changes. thought it might be a bad relay but of course it was not that simple. i have replaced the electronic ignition module on the distributor, the fuel pressure regulator, & the fuel pump in the tank. is there something else involved in getting the power to the fuel pump in the tank? anybody have any ideas at all????

Follow this link.http://www.automotiveforums.com/vbulletin/search.php?searchid=1488772
There are several good posts on troubleshooting this issue on Fseries trucks. Or you can do an advanced search, and pull up some more. Good luck.
Later
Ed