What would cause both fuel pumps to stop working after a 1990 Ford F150 truck warms up?

Fuel pump relay, maybe

Remove the ingnition mudule located on the driver's side fender, no on top of the fender skirt, on the fender near the firewall. I think it's a 10mm. It looks like a black box(1 1/2" x 4") mounted in an aluminum heat finned casing. OR it is attached to the bottom of your distributor 9(same physical description minus the aluminum piece). Now that you've found it and taken it off, take it to your local autozone and have tested at least 8 times in order to heat it up to normal operating temp. If it fails, BINGO! You answered the million dollar question that plagues and drives Ford owners insane trying to figure it out. You see, this module when it decides to comletely fail will stop your truck from firing and will stop your fuel pumps from pumping, leaving you dead. NO spark, No fuel.

CHECK YOUR RELAYS.......POWER AND FUEL PUMP RELAYS, ONE OR THE OTHER

CAN OPEN WHEN HOT RESULTING IN FUEL PUMP SHUTDOWN: