As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER STARTING APU, GROUND CREW SAW FLAMES COMING FROM APU. IMMEDIATELY SHUT DOWN. REMOVED FROM SERVICE. REMOVED COLLAR & RESET THE CIRCUIT BREAKER. INTERROGATED CDS, FOUND NO CURRENT FAULTS. FOUND BOTH IGNITORS FLAGGED IN FAULT HISTORY. R & R BOTH IGNITORS IAW AMM 49-40-04-000/400-801. PERFORMED FAILED START ATTEMPT INSPECTION IAW HS 49-0008. GROUND RAN APU WITH NO DEFECTS. ACFT RETURNED TO SERVICE.