New to NICO -- Need help with my new D21

[BeeDoo]

Good morning,

New to the forum and looking for some serious help! Here's where I'm at....

1986 (or maybe 1986.5 -- build date April '86) D21 SE V6 3.0, 4x4, Manual

HERE'S THE VIDEO if you don't want to read everything: https://streamable.com/x9m6kb

When got truck:
It had been sitting for 6 months, dead battery.
It would crank when hooked up to jumper cables, but only would start/run with gas poured down the throttle body. Only run on gas poured in -- just a few seconds.
No lights, no turn signal, no blower, no accessories.


Since then:

Replaced fuel filter
Replaced TPS (code 43 was showing on ECU -- replacement cleared code)
Cleaned injectors (they now spray fuel with key turned on)
Replaced ECU (code was 31 -- replacement DID NOT clear code)
Checked fuel pressure in line (36 PSI)
Checked Fusible links for continuity -- seem OK
Checked/Swapped Main Relay and Fuel Pump Relay -- seem OK
Checked fuse box -- NO POWER to any accessories. Only power to "Fuel Pump" and "Fuel Cut Off"
Checked connections in back of fuse box.. Couldn't see/determine any issues with connections.

Now: VIDEO: https://streamable.com/x9m6kb

1. Truck will start up and run WITHOUT fuse for fuel pump. It will idle indefinitely, but if touch gas pedal, will starve for fuel and quit.
2. When insert fuel pump fuse while running, truck dies immediately -- see video below.
3. When insert fuel pump fuse with truck off, turn key to "ON" position, fuel pump hums/turns on and injectors mist fuel into throttle body.
4. Still no lights, dash lights, turn signals, blower.

Other potentially helpful information:
1. Previous owner said everything worked (lights, blower, etc) until nothing worked -- it wouldn't start, and then no lights, blower, etc.
2. Checked voltage at battery WITHOUT truck running ~ 12.4 volts. Checked battery WITH truck running (though idling very low, under 1000 RPMS I'd guess), ~ 12.3 volts. I believe it should be 14 volts with alternator, but perhaps that is due to a very low/poor idle.
3. I have checked as many wires/connections as I can without taking apart the wiring harness, etc.
4. I have tried unplugging TPS, MAF, and other random connections one at a time -- none have made any difference.

That's where I'm at now. I guess my next plan is to try a new battery, new alternator, new relays....
I feel there are two issues.
1. The lights, dash, blower, accessories not getting power
2. The engine completely cutting out when fuel pump comes on.

I don't know if these are related or not....

Thanks for the help!
Steve