I have been running a old version MSD-10 that uses the pro power coupler it has was worked great for the last 3 seasons but after a engine rebuild this year it wont even try to fire.I bypassed the coupler and it starts right up. I sent my pro power coupler to MSD and it checked out good. I put it back on the car and same thing, It wont start. I bypassed the power coupler and it fires right up. Would anybody know if there should be continuity threw the coupler like you do threw a coil? Could it be my ignition box? Any help would be great.