I had the same thing happen to my ex wife with a 1975 fury with a 318. Chain jumped and with it cranking out of time, she thought the battery went bad. Here comes a pump jockey and same thing. She could not understand why the engine made so much noise when it started. She ended up bending 12 of the 16 valves, so timing chain, and a valve job later, car ran great for another 5 years after I sold it.