The Coronet hasn't started in two months. Turn the key and everything goes dead, like someone disconnected the battery. Wouldn't start when jumping the starter relay. Wife and I had been busy replacing the downstairs carpet with LVP (luxury vinyl plank) every weekend so the car sat. Project is now finished so today I pulled the ignition switch and bench tested it with an ohm meter for continuity. Each terminal has continuity but the resistance seemed high - over 0.1 ohm.
I pulled the key tumbler and cleaned the contact point and smeared on dielectric grease. The bottom of the ignition switch barrel and the tumbler contact point were covered in a black soot, felt like fossilized grease. After cleaning and assembling, the switch bench tested something like 0.04 ohms. Reinstalled the switch and she fired right up. I love cheap, simple fixes!