What was found
PILOT REPORTED LT ENG WOULD NOT LIGHT OFF ON START AND THERE WAS NO AUDIBLE SNAPPING SOUND. THE BOX HAD 24 VOLTS AND GOOD GROUND. ANOTHER EXCITER BOX INSTALLED AND IGNITER CHECKED. A SNAP FROM INBD IGNITER HEARD AND ENG WAS COWLED UP, ENG STARTED, AND AIRPLANE RETURNED TO BASE. ENG HAS 2 EXCITER BOXES AND APPARENTLY BOTH BOXES FAILED. ACFT HAD UNDERGONE A PHASE 3 AND 4 INSPECTIONS 24 HOURS PREVIOUS AT 598 HRS. IGNITERS WERE CHECKED AND WORKED. BOXES POSSIBLY DID NOT FAIL AT SAME TIME AS ENG STARTED ON ONE IGNITER. OTBD EXCITER CIRCUIT CHECKED. BOTH WERE GOOD AND 2 EXCHANGE EXCITER BOXES INSTALLED. IGNITERS REMOVED, INSPECTED. ALL OPS OK. IGNITER REINSTALLED, ACFT WAS COWLED UP, RETURNED TO SERVICE.