912uls charge coils test for output,unplugged and cranking engine

Having odd problems with 174 hour 912uls, all ohm tests are good  but having 2 different ignition coils occasionally firing other not firing at all, temporarily wired another coil into plug at harness, still no firing,  as a side note I touched my volt meter to the primary white and blue and only observed well below one volt ac or DC but no pulsing of voltage - to build up and collapse coil - to create spark