If the points are open, bridge something like a screw driver across them. Whenever you break the bridge, the coil should pop a spark. If it sparks then, look for something like moisture in your distributor cap. Whenever the engine, the condenser loads while the points are closed and then discharges when the points open and that is what causes the spark. If it does not spark when you bridge and break at the points, I would suspect a bad condenser or your breaker plate is not grounded.
