1991 Ford F-250 fuel pump rely

I have a 1991 Ford f-250 that has some fuel pump trouble. The rear pump is disassembled, but the front is still in tact. My problem is that, of corse, the truck does not run.
I have 12+ volts at the hot side of the fuel pump relay, but when the key is turned on I am only getting 2.5 volts on the pump side of the relay.
My first thought was that the contacts in the relay were bad. I replaced the relay, but still have the same trouble.
The grounds have been checked, and all have checked out o.K. I have also checked the roll over valve and it is functioning fine. The connections at the relay have been checked for corrsion
I can jump out the front pump with 12 volts and the "old red girl" will fire right up.
Any help will be greatly accepted. Thanks.