As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
THE FLIGHT CREW REPORTED THAT DURING START OF THE APU OF SMELLING EXHAUST FUMES. SUSPECTED THAT THE APU BLEED VALVE WAS NOT SHUTTING COMPLETELY. THE MAINTENANCE TEAM DETERMINED THAT THE APU BLEED AIR BUTTERFLY VALVE WAS INOPERABLE. THE VALVE WAS REMOVED AND AN OVERHAULED UNIT WAS INSTALLED. OPS CHECKS WERE SATISFACTORY AND THE AIRCRAFT WAS RETURNED TO SERVICE.