BE 58 pilot reported having a right engine failure on initial climb. Pilot feathered engine and returned to land. Post-flight a mechanic found a loose fuel line B-nut on the fuel input line to the manifold.

Narrative

Minutes after departing ZZZ the RH engine failed.No abnormal indications or sounds preceded or accompanied the failure. The loss of power was swift and silent. I feathered the RH propeller; secured the engine and returned for a safe landing at ZZZ. After landing; a strong fuel order was present under the RH cowl and fuel spray was observed on the upper cowl surface. Activating the boost pump created a spray of fuel within the cowling on the top of the engine case.A mechanic removed the cowling and discovered the B-nut on the fuel input line to the fuel manifold (spider) was loose. The pump was activated and the juncture with the loose B-nut was confirmed as the source of the leak. The fitting exhibited no signs of damage. The B-nut was tightened; fuel pump activated to pressurize the fuel system; and no leaks were observed at this location. The aircraft had undergone an extensive annual inspection 13 flight hours prior to the engine failure. During the annual; the TCM fuel injection setup procedure was performed and fuel flows and mixtures were adjusted by the mechanic based on the test results; as recorded in the engine logbook. The TCM setup procedure prescribes the removal of the fuel line at the leak location to install a 'tee' fitting for the temporary installation of an inline pressure gauge for use during the procedure. No additional maintenance was performed on the RH engine by any parties in the 13 flight hours between the annual inspection and RH engine failure. The aircraft was stored in a security camera monitored hangar when not in use by the owner; and no other parties accessed the aircraft.The apparent root cause of the inflight fuel leak and engine failure was improper torquing of the B-nut at the juncture of the fuel line and the fuel manifold elbow following the performance of the TCM fuel injection system setup procedure.