Probe the (-) terminal on the coil with a test light. (Connect the test light wire to a good ground) The light should be illuminated when the points are open, and it should go out when the points close. if it's on all the time, points open or closed, you've got an open circuit between the coil and the points. (Dirty points, broken wire inside the distributor, etc.) If it's off all the time, you've got a short, maybe the distributor primary wire shorted to ground upstream of the points, shorted condenser, or a ground where the stud goes through the distributor housing. If it's working right, the light will flash on and off as the engine is cranked. The on-and-off current in the primary circuit generates the magnetism necessary to develop the high voltage in the coil's secondary windings.
Jerry

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