[Moriarty]

Alright, now we're getting somewhere. Connecting straight to the solenoid pos worked fine, so I figured the next step was to connect to the brown terminal of the ignition. When I did this I happened to hear a very faint clicking or intermittent buzzing. After turning out all the lights and repeating, I discovered some sparking inside of the clear connector for wire bundles labeled D (to I think C). I'm out of time for debugging today, but will take that apart (maybe tomorrow) to figure out what's going on there.

Thanks for all the help! Definitely feel like I've leveled up my electrical troubleshooting skills through this.