Ok so i've done some searching and can't seem to find my specific problem anywhere. I have an 83 (title is typo) FB with a 12a, MSD 6A (wasted spark setup), factory trailing, Mikuni sidedraft, e-fan and relocated battery. I drove with all this stuff for several months before my problems started.

I went out one day to try and start the car after it had been sitting about 5 days, and i didn't get power to ANYTHING except the headlights. So i started going through fuses and found nothing wrong. The factory fusible link setup was removed long ago (before the MSD box, e-fan or battery relocation) and a regular 4 fuse box was installed identical to this


All these fuses are good, as in they have 12VDC at both sides, and i checked continuity across each individual fuse and they are fine.

Recently i replaced the ignition switch thinking that was the problem and the car worked fine for a week or so, then the problem returned intermittently. One time while i had no power i went under the hood and started moving wires and tapping relays and the power came back. I tried again today when i had no power and still have yet to get the power to come on...and now i have no power to anything except the outlet of my fuse box...so somewhere between the fuse box and all my accessories i'm getting an interruption...

Could i be lucky enough for it to be just a bad relay, or do i need to tear into this harness? I was planning on a 13b install in the near-ish future and was gonna reroute all the wiring through the fender area at that time to clean up the engine bay and it would be nice if i only had to tear into the harness once...

 

Ok so apparently even though i was getting 12VDC and continuity across all my fuses, one (i'm assuming the "main" one) just wasnt transferring enough juice through it to power anything up...i just swapped around a couple fuses in the main box and everything fired right up...so i'm gonna go get some replacement fuses and replace all 4 in the box...should have tried that sooner...fml

 

Haha, glad you found it! So quickly at that

 

Glad you got it figured out! I'd recommend replacing that setup with an FC, FD or 626 fuse box that use the square replacement fuses. They look factory and are extremely functional - I love them.