Power from Taillight is wired to fuel sending unit... Check!

sazzlefrats said

Maybe related to that, I am missing the final pigtail to the right rear lamp, and the key was not in the ignition. But I would think with the ignition off, there should be no power except to the horn, hazard and light (because those typically work whether the key is in or not).

BTW I'm testing for voltage by touching the tester wire to the wire and the other lead to the body of the car.

Click to expand...

Should not be power to it "at rest" pigtail or no. You've got something crossed up in there somewhere. I'm not sure I can help you further, as obviously the harness has been "hacked." There's only so far one can go on paper as here's the thing:

First, there's the possibility of just plain mistakes in OEM diagrams

Second the harness could be hacked

Third, the harness could be damaged, IE crossed and shorted.

You simply have to "dig in" and find it.

I'm so used to this sort of thing in old, hacked stuff that I learn to assume nothing and suspect the worst and check everything.. When you do that, it actually makes things easier.