Hi,
I don't know what's happening between you and CB but it doesn't look nice. Are you are both setting at a dinner table in a Harry Potter movie? CB is pretty down to earth with simple and I would say righteous suggestions in many cases. You might want to keep him on your side.

I think from your thread statement about the 25 Amp fuse working but being an open circuit tells me you need help in electrical terminology. A Short is just exactly that! It lasts only for a short time, as it burns a fuse or its wire up! Then it's an open circuit!

Bricktank dropped you a Link to the fuel relay system. It shows you that the ICU and ECU are turning on and off the pumps. That is their sole responsibility. If your ignition key is off, then so are the two computers. They should NOT be ON either! So this definitely puts the relay in the OFF position.

If the relay is on all the time and the pumps are running, either because relay is jumped on, stuck on, or held closed internally.
I do this sometimes with a rubber band or a shoe lace to bypass the computers if I suspect one or the other is not doing its job. In such cases, a car will not run.
That may have been the PO's previous problem.

If the relay has both coils turned ON, or the contacts are closed, by any means available, the orange wire of the AMM will ON too! CHECK and see if it is ON as well, all the time!
This may tell you something.
If you pull the relay completely out, this kills both circuits. That tells you nothing.

You see, the relay handles two separate circuits. Either one is controlled independently under operational conditions but the ICU ultimately powers both coils on the red wire. The coils are grounded by the computers. The circuits are housed together and switched.

In '84 they were two separate relay boxes and you could lose only one relay due to a bad winding.
If it was the pumps relay you could switch them around because they were alike.
You turn the key and test the pumps to run when cranked. It was then, you knew the other relay was bad because now you heard the pumps running.
But Now, with the bad relay there, the injectors/AMM do not work. If You manually close that injector relay, the AMM is on and the engine will run.

Only trouble is, it's now on all the time and you won't hear it! This is Not good as you are still running the battery down.
It's better to switch it back, manually close it, to hear the pumps. Let the other injector relay be controlled.
Then what do when you get to where you need to be, you can pull the fuse or battery cable and kill everything.
Its suppose too work like that to be more Safe!
It will not take you long to get tired of that and fix it properly.

That's where you are now! Tracking down what been bypassed in relation to the color wires on the fuel system relay circuits.
Question is how it's getting power to both the injectors and pumps. Most likely jumping power to the relay red wire or figuring out the contacts are closed or bypassed using a grounding wire.
You have to think on both sides of the relay or the circuit operation as Volvo planned it.

If this all works for you, in some way, be nice to my buddies on the BRICKBOARD! (:-)
Phil

PS, If you want to see a hairy way of addressing what might be wrong with a car look at this and cringe!
https://www.volvoclub.org.uk/faq/EngineFIComputer.html#Intermittent_Stalling_Bad_ECU