As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING ENGINE START, AFTER ENGINE START SELECTOR TO IGNITION START AIR PRESSURE DROP FROM 45 TO 0, ABORTED START ON 2ND ATTEMPT APU FAILED. TROUBLESHOT AND FOUND SURGE CONTROL VALVE FAILED. R & R SURGE VALVE IAW AMM 49-51-52-000-801-A. THEN PERFORMED OPS CHECK AND OPS CHECK GOOD. APU STARTED OK. ACFT OK FOR SERVICE.