First, do a thorough visual inspection of the wiring harness from the connector under the cab back (the wire might still be PK/BK). If you don't find anything, disconnect the connector under the cab, clean it, inspect its pins, apply dielectric grease and reconnect.
Last, pull the bed or drop the tank and inspect the connector where it goes into the top of the tank.
You haven't spent any $$ yet, so either throw a $12 Fuel Pump relay at it or swap it with one just like it. I'd do one or the other before I pulled the bed off.
Only things left are the ground, which is probably common with other subsystems, the inertia switch, which appears to be good, and the pump assembly itself.
2000 2.5 MO5D 4.10 one-wheel drive DD - gave to my older son
1990 STX 87 2.9 going in.....Junked it
2000 3.0 4WD M05D 4.10 S-cab Off-Road package with 235-75-15" tires, hotrod DD, lol