What was found
(B18717) EXPERIENCED TWO CAN’T SHUTDOWN ENGINE EVENTS ON NR 3 ENGINE; FIRST ON JAN 27,2012 & SECOND ON FEB 4,2012). DURING TROUBLESHOOTING, GROUND CONFIRMED THAT THE HMU FUEL SHUTOFF VALVE STUCK IN OPEN POSITION & NR 2 HMUS WERE REPLACED. SHOP REPORT REVEALED SCREW STUCK IN BOTH HMU SHUTOFF VALVE CHAMBER & SHOP CONFIRMED SCREW NOT PART OF HMU. FOUND SCREW CAME FROM BYPASS VALVE CAGE OF FUEL FILTER. THERE ARE THREE SCREWS ATTACHED TO BYPASS VALVE CAGE TO FUEL FILTER & NR 3 ENGINE FUEL FILTER INSPECTED & FOUND ALL 3 SCREWS LIBERATED & MISSING.