On March 13, 1999, approximately 1500 mountain standard time, a Gulfstream Aerospace G-IV, N411WW, received minor damage to the left engine while in cruise flight near Durango, Colorado. The airline transport pilot captain and the airline transport pilot first officer were not injured. The airplane was being operated by Zeno Air Inc. of Chicago, Illinois, under Title 14 CFR Part 91. Visual meteorological conditions prevailed for the cross-country repositioning flight which originated at Santa Barbara, California, approximately 1 hour, 30 minutes before the incident. An IFR flight plan had been filed with a destination of Chicago Midway Airport, Chicago, Illinois. According to the captain, the airplane was cruising at 41,000 feet msl when the crew noticed low fuel flow and low EGT readings on the left engine. He further stated that the oil temperature and fuel temperature gauges began to rise on the same engine. He requested clearance to descend, and as he reduced the throttle, the fire light on the left engine illuminated. He pulled the left fire T-handle and the fire light extinguished. The crew secured the engine, requested emergency equipment be standing by in Durango, and landed without further incident. Postaccident examination by maintenance personnel from Gulfstream revealed that the lower forward area of the left engine nacelle was damaged by fire. Further examination revealed that an electrical wire coming from an alternator in the engine had been chaffing against the number four fuel line. Gulfstream has prepared an Alert Customer Bulletin No. 26A, dated March 17, 1999, to notify all owners of Gulfstream IV's of this problem.