As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT 5855 - IAD - FLIGHT CREW REPORTED BURNING SMELL IN COCKPIT WITH APU AND PACKS RUNNING. IAD MX REMOVED AND REPLACED FUEL LINE FROM FUEL FILTER TO FUEL CONTROL UNIT AND PERFORMED OPERATIONAL CHECK SUCCESSFULLY. ACFT WAS APPROVED TO RETURN TO SERVICE.