Interesting issue, When tach is hooked up car won't turn off Options

[oildrips]

Lots of progress today/tonight. All vacuum lines rerun, dwell/timing set, new oilnpressure switch, oil changed, and I've isolated the issue where the car won't turn off when the key is removed, but there's some funky stuff happening.

So, before I started working on stuff, the car would start, and the engine would continue to run without the key. You'd have to stall it to shut it off. Once off, it would maintain power to the gauges (the generator light stayed lit), so you'd have to undo the battery. to reset everything.

I traced everything back to the tach. Without the tach signal wire hooked up, the key works fine. Engine starts/stops with the key.

Now, after doing all the work. I started the car, and decided to try the tach. Hooked it up, and sure enough the key didn't work to shut it off. I pulled the positive cable off the battery, and the car kept running on its own. I had to pull the coil leads to kill the engine.

Thoughts?