Practically Classics Forum

Car should still start with a dodgy capacitor. What it does is stop- or minimise sparking across the points when they open.

A dodgy capacitor will make the car run badly when it does start.

That assumes o/c, but if the condenser fails s/c then the car won't be starting any time soon. Though the o/p did mention a weak spark, so I'd probably go back to the idea of that rotor arm. Even the older, Bakelite ones can leak to earth occasionally.