As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AFTER TAKEOFF FLIGHT CREW PERCEIVED THE ODOR OF FUMES IN COCKPIT AND ELECTED TO RETURN TO ATL MAINTENANCE BASE. INVESTIGATED BY MAINTENANCE AND FOUND FUEL SHROUD GOING TO APU TO NOT BE PROPERLY SEATED. REPLACED O-RING AND SEAL TO INSURE INTEGRITY OF FUEL LINE SHROUD. AS PRECAUTIONARY MEASURE REPLACED COALESCER BAGS.