Hi Roy Jimmy.
I had some trouble with my twin F-15 some years ago. And this was solved by wiring a connection to the negative on the pump pack, to the turbine.
The ducts got the same wiring, but just a short one to one screw holding the nozzle.
All long servo-leads got the same treatment. Leave the minus on the RC, DO NOT mess with this!
I used thin alu-tape to shield the leads. Connection on the servoleads was made near the pump-pack, but the clou is to have just one piont of connection for each object beeing earthed.

This solved it all for me back then, but the best is not to cure a syndrom, but instead get rid of the cause...(Yes, you have tried almost everything till now) Mine was also Fadecs as well, but I doubt your Fadec is the reason.
I think you have a serious interference problem due to the setup.
Also be sure not to have any alu close to the aerial wip! The alu sure will consume the most of the received signals.

If you do like i did, your setup will be like there was no longer servoleads than five cm each, depending of how thouroughly (how much in lenght) you have taped the servoleads) Interference will not enter your system due to the equal electrical potensial in all metal parts as this is absorbed by the negative... Think of it as a vacuume.
Remember, you must use the MINUS on the pump pack, no other!

I had manually start ECU`s, and had no trouble about voltage the engine with the pump pack.
It might be a different matter with a autostart..

Hope you a closer to a solution.

Regards

Gudmund