As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
DURING L ENG START AT 50% WHEN ENG START SELECT CYCLED TO AUTO A STRONG BURNING SMELL (BURNING PAPER & RUBBER) WAS SMELLED. FOUND LT AND RT RECIRC CHECK VALVES DAMAGED AND LT RECIRC VLV WAS INJESTED INTO LT RECIRC FAN RMVD LT&RT CHECK VLV AND LT RECIRC FAN. (7800198) (AIRCRAFT GROUNDED)