As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ON CLIMB OUT WHEN AC WAS TURNED ON ODOR FILLED THE COCKPIT AREA. FLIGHT CANCELED AND RETURNED TO BASE. AIR PUMP MFG BY IMPACT INSTRUMENTATION FAILED AND CAUSED ODOR TO FILL THE COCK PIT AREA PUMP PN E-428K SN 0609003 WAS THE PROBLEM, AND IT FAILED.