What was found
ON FINAL APPROACH INTO LGA, THE CREW PULLED FLAPS FROM 8-20, BUT FLAPS DID NOT MOVE, AND A FLAP FAILURE MESSAGE APPEARED. THE CREW EXECUTED A GO AROUND, AND DECIDED TO DIVERT TO JFK TO LAND ON A LONGER RUNWAY. THE CREW DID DECLARE AN EMERGENCY. THE AIRCRAFT LANDED AND WAS ABLE TO TAXI INTO GATE. THE CREW WORKED WITH MAINTENANCE AND WAS ABLE TO RESET & DEFER THE FLAP SYSTEM. C/W AD 2009-06-12 PARAGRAPH H.6.I AND T.O. 27-050-004-09 REV. Q. FOUND LH BPSU OUT OF RIG. RIGGED LH BPSU IAW CRJ 200 AMM 27-51-10-830-801. RIG CHECK GOOD. OPS. CHECK GOOD. THIS CLEARS MEL.