Why do I have low voltage at the fuel pump - 1982

I have an 82 vet and the fuel pump (electric in the tank)will not activate. The fuel pump fuse is good, when I turn the ignition key "on" and test the leads at the pump it registers 8 volts. When I connect a remote known good ground and a remote known 12 volts to the pump it will not activate. (however these same remote known leads will power a loose electric fuel pump I have.) So, I understand the pump is no good and I will replace it. But why do the power supply leads at the pump only supply 8 volts with the key on? That 8 volts is not enough to run my loose test fuel pump and it will not be enough current to run the replacement pump. What do I do next??? - Thanks for your tips......John

I had the same problem with my CE. DON'T replace the pump until you check the fuel relay. that was rong eith mine. It was only a $20 part. I would check there first.