Yanmar 2GM20 won't start when sensors wire connected to Key switch.

[cat ballou]

I can start the engine when Key is off and I'm touching the Push-button wire to the back of Hot terminal on key switch and also will start when removing the sensors wire from Key switch terminal, using push button and key as I would normally.
So I think I narrowed the problem to the sensors wire on back of Key switch terminal.

Any helping ideas on how this can be corrected is much appreciated.