78 js440 unusal spark

[Slp1997]

I got a 1978 js440 given to me for some work and it has an unusual spark problem. When you are pushing the start button the engine will turn over and with the plugs out and grounded it will not spark.... unless I rapidly push the stop button at the same time I bought a completely new e-box for it and it didn't seem to help any I even tested all the components in the e box and everything ohmed out correctly any one have an idea on what's goin on.... also I tested the stop button for continuity and it seemed correct it read open when not pushing and grounded when pushed. Any other ideas would be appreciated