What was found
5.7 HOURS AFTER COMPLETING AN ENGINE INSPECTION, WHICH INCLUDED CHANGING THE HMU FILTER AND PACKINGS, THE PILOT UPON HIS POST FLIGHT WALK AROUND NOTICED FUEL ON THE UNDERSIDE OF THE FUSELAGE. TO ASSIST IN TROUBLESHOOTING THE PROBLEM, THE PILOT THEN PROCEEDED TO TURN ON THE AIRFRAME BOOST PUMP. THE FUEL WAS FOUND TO BE LEAKING FROM THE ENGINE OVERBOARD DRAIN. THE MECHANIC WAS ADVISED OF THE PROBLEM. AFTER TROUBLESHOOTING THE SYS IT WAS DISCOVERED THAT THE HMU FUEL FILTER PACKING HAD BEEN CUT DURING THE LAST INSPECTION 5.7 HRS PREVIOUSLY. MECHANIC CHANGED THE PACKINGS AND TEST RAN THE ACFT NUMEROUS TIMES, WITH NO DEFECTS NOTED. PAPERWORK WAS COMPLETED AND THE ACFT WAS APPROVED FOR RETURN TO SERVICE.