Tripped me up, and I was just modernizing my 273's wiring. I ASSumed that IGN1 got +12 V all the time, and IGN2 gave +12V only during crank (to bypass ballast). Turns out that during cranking, IGN2 is the only one energized. I should have tested ign switch with a multimeter. Finally figured it out when it wouldn't fire during cranking, but fired as soon as I let go of the starter. If you aren't using the ballast, just connect both ign wires together. I jumpered them at the ign switch.
