1999 Ford F-150 fuel pump

Check fuel pump relay and wiring back to the fuel pump

Are you testing the volts at the relay or at the pump?

Mark the relay and switch it with a similar one
test at the relay for volts out

Check fuse #10 its 20A
pink/black wire should have battery volts when key 1st on and when cranking
if not go back to the inertia switch if have it power at the switch then suspect and check wire between switch and pump

if no volts check for volts at the grn/yel wire
if have power replace switch
if no power check wire between switch and relay

Checked the fuse and its OK?

Remove the relay and check cavity #30 should have battery power if so use a fused wire and jump cavity #30 to cavity #87 DR/GRN/YEL wire
that should activate the pump if wiring and circuit OK if not have to check by the spare tire for a module and if have one check for power in and out

Use a fused wire to power cavity #87
that should activate the pump on or off

Did you try new relay

Use a test light
turn key on check cavite #86 it should have power do you?
Red wire

Jumping 30 to 87 should get the truck starter
if pump coming on all wiring should be fine from the relay to pump
have to check relay control circuit

RED WIRE SHOULD HAVE POWER
CHECK FUSE #18 IT 15A UNDER HOOD FUSE BOX
LEFT SIDE OF ENGINE COMPARTMENT
IF FUSE OK CHECK WIRE