^^That makes no sense at all but it brings up ANOTHER problem^^ ---By that I mean it makes no sense that this jumper would have anything to do with ???the door being closed or open????
The polarity of the pickup wires are IMPORTANT because when you change polarity it moves spark timing in relation between the pickup (the spark time event) and the rotor/ cap contacts. That is, the rotor may not be pointed to a cap contact when the spark happens. This has become a "modern term" known as ROTOR PHASING. Google it. I would check it as we don't know if it was correct earlier or now. In any cast, if that jumper really changed polarity, it is an issue with or without, one or the other