09 DTS fuel pump
 

My Cadillac fuel pump has been replaced and it's still not turning on I have power running straight to the battery from the fuel pump and it turns on just fine start the car up it runs just fine however when I have the connector plugged into the fuel pump running to the fuse box no start I change the relay cuz that's what what I noticed first and was burnt out so I change the relay. And then the fuel pump come to find out my fuel pump was fine however the relay was burnt out no I've been told that I have to replace the rear fuse box is that true. If not can I disassemble diffuse box and check the wires that are leading directly to the relay to the fuel pump because between the fuse box to the fuel pump is my problem it's not getting power it is not running to allow me to start the car

We really have no way of knowing what your issue is without some electrical testing. Are the correct voltages and grounds getting to the relay? Is the relay trying to work? (clicking when turned on) Is the ground good to the fuel pump?

I will say I've seen issues at the rear fuse blocks in these cars, poor connections, wires and terminals getting hot. Without knowing more, I would say thats a fair guess that it may be the culprit. I would not recommend taking the fuse block apart unless you are experienced in that sort of work. But you can remove it enough to see the wires and terminals coming in - you may be able to see something burned or melted.

Replace the relay again. Or have someone start the car, while you are touching the relay, you can feel the relay clicking.