Fuel pump wiring issues

[Bboy]

I have been scanning the forums trying to find answers and am out of ideas... I've been checking all the volts at the fuel pump relay at the FP plug and at the inertia switch...

This is an 88 bronco 2 that I've pulled the entire wiring harness, engine, transmission from a 93 Ford explorer (so everything is pretty much explorer) I've got a 1990 bronco 2 fuel pump (fits bronco tank but runs same pressure as explorer) when I run the key I don't hear the pump (brand new pump) after checking the wiring I used a battery and some jumper wires to give the pump positive and negative power directly from a battery and the pump turned on so I knew the pump works. When I turn on the key it gets 12 volts and then drops to 6.49 volts after a few seconds (to my understanding that's about normal but could be wrong, also I have spliced in a bronco plug here but it is getting power through there). At the relay I have the constant 12v (11.95v but battery was getting low from tracking this all day) on one, 12v when key turns on and a 6.45 on the last. Inertia switch has 6.73 on both wires

What else can I check and are those all correct? Really out of ideas here. Pretty new to wiring issues so use simple terms when describibg what I should check next

 

[Bboy]

Update and bump. I probed the ground wire at the fuel pump and hooked it directly to ground and the pump worked with the key providing the power... What's confusing to me is that's also where I tested ground with the multimeter and I was about to get readings off it. I also probed the test light into the light blue/orange wire up next to the fuse box and the light was super dim like it wasn't getting a good ground... Is that the wire that is grounded with the computer? I'm not sure where to trace that wire to because it goes the computer to the fuse box so not positive what to do with that next?

 

[410Fortune]

How are your battery terminals?
The negative terminal has 3 leads one to the firewall one to the frame and it goes on to the engine/drivetrain

All of those connections must be good and clean and tight. Cables cannot be internally corroded

Good Job diagnosing the fuel pump power issue you have ruled out the fuse the relay the inertia switch and all the wiring between them

 

[Bboy]

How are your battery terminals?
The negative terminal has 3 leads one to the firewall one to the frame and it goes on to the engine/drivetrain

All of those connections must be good and clean and tight. Cables cannot be internally corroded

Good Job diagnosing the fuel pump power issue you have ruled out the fuse the relay the inertia switch and all the wiring between them

I've checked and rechecked grounds (both cleaning them and checking continuity with a multimeter) to day I started at the back checking continuity down the ground wire. Also checking continuity end to end to make sure there aren't any breaks in it and that I have the right wire. I traced the black ground wire to the drivers side inner fender plug where it then becomes purple with yellow strip and crosses the engine bay into the pcm, I did not have ground the entire way... The light blue with orange wire that comes from the PCM relay into the pcm has ground at the PCM but for some reason I'm not getting ground back out of the PCM through the purple/yellow wire... I also have the test plug fuel pump wire grounded so it should be giving consistent ground if I'm understanding correctly... What would be causing this? Is it a bad PCM? Might be able to barrow one from my buddy's explorer to test that theory later or am I wrong in thinking that the text plug being grounded would not show me ground that whole way? I've at least eliminated the possibility of the ground wire having a break. Definitely going crazy just checking grounds over and over