Originally Posted by RamTech
You can't rule out the pump if the wiring to it is defective. Sure you can try rigging up a battery and some jumper wires to test the pump, but I've seen a guy set himself on fire trying that stunt. Gaining access to the pump connector and checking for B+ with the relay jumpered via volt meter and then checking continuity to ground is an easier and safer way to go.
I would never recommend anything to anyone that is obviously dangerous, certainly you cannot rule out faulty wiring with a fuel pump tester, but you can atleast get a place of where to start, you're a technician and know that when fuel pumps fail, many times they do show some amount of pressure and even if they doesn't you still can say well it is either the pump is bad or the wiring is faulty. Next step, take a volt meter and wire it across the pump motor terminals and then put the key in the ignition and turn the key to the on position and see if there is a voltage drop, if there is than the wiring if fine and the pump is faulty. The motor usually doesn't die, the pump assembly just wears out, but you know this.