As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
MSP - FLT 421 - WHILE PERFORMING ENGINE START THE IGNITION WAS INTERMITTENT FROM FOURTY TO FIFTY FIVE PERCENT. THE TACH GENERATOR SIGNAL WAS INTERRUPTING THE SPEED SWITCH POWER TO THE START CONTROL RELAYS. THE RPM INDICATION OPERATED NORMAL. THE TACH GENERATOR WAS REPLACED AND THE AIRCRAFT RELEASED. (W)