Fuel pump test jumper either bypasses or turns on the CO relay that supplies power to the fuel pump:
- http://www.4crawler.com/4x4/CheapTricks/index.shtml#FuelPump

Normally the AFM keeps the CO relay on when the engine is running, make sure that is working:
- http://www.4crawler.com/4x4/CheapTricks/AFM/index.shtml