1972 dart - stopped running while at 50 mph ? no warning

Bend up the tab on the rotor a bit to make sure it is making contact with the cap.

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By the looks of things, you probably have the old heavy slow turning Original mopar starter In it yet too. They suck a lot of electricity away from the ignition system especially after 50 years of age wear and electrical internal corrosion.

Put in a new Mini Starter that fit the Dodge Dakotas, they start like they have fuel injection with those.

Spins them fast and draws way less juice. More juice to power your ignition.