Spirit of the South

After reaching a cruise altitude of 9500 feet the pilot noticed smoke coming out of the left engine cowling. He then proceeded to reduce the left throttle but was unable to move the lever. According to the pilot the fire was extinguished when the left fuel selector was turned off but relit about 3 minutes later. During the emergency descent that followed all electrical power was lost and the copilot was instructed to crank down the landing gear. During landing roll the left gear collapsed as the wing continued to burn. Engine examination revealed that the fuel pressure return line located on the firewall was finger tight. The other fitting was secure and the maintenance manual call for 30-40 inch-pounds of torque on that fitting. The pilot did not follow approved emergency procedures for an inflight wing or engine fire.