Ok I started out with a 83onvertible V6. I removed all the wiring in the car and replaced it with a 87 mustang GT harness ( the whole thing ). So when I turn the key the dash lights turn on and the box by the fuse box clicks but nothing from anything else. None of the relays are working ( fuel pump relay or EEC relay). I have replaced the relays and still nothing. Any help would be appreciated as I am getting very frustrated. I have checked all known connection but still nothing. I can make the fuel pump run by a jumper wire so I know the fuel pump is good. Thanks in advance.

 

sounds like a ground problem to me.

I would start there, triple check and upgrade all your grounds.
Factory ground set-up is mediocre at best.

 

Ok replaced all the grounds and still nothing. How do these relays work. I bench tested with a battery and the new ones test fine. What will hold out the fuel pump relay from kicking in? I am lost.