On August 22, 2003, at 1120 mountain standard time, a Cessna 150C, N7909Z, lost total engine power during cruise and collided with a tree during the forced landing near Tucson, Arizona. The pilot/owner was operating the airplane under the provisions of 14 CFR Part 91. The private pilot and one passenger were not injured; the airplane sustained substantial damage. The cross-country flight departed Gila Bend Municipal Airport (E63), Gila Bend, Arizona, about 1030, and was en route to Ryan Field (RYN), Tucson. Day visual meteorological conditions prevailed and a visual flight rules (VFR) flight plan had been filed. In a phone conversation, the pilot reported to the Safety Board investigator-in-charge (IIC) that during a cross-country flight from Gila Bend Airport to Ryan Field, the airplane's engine sputtered, followed by a loss of power. The engine quit and he made a forced landing. He felt that the engine stopped due to fuel exhaustion. In a written statement, the pilot reported that he departed from Imperial Airport (IPL), Imperial, California, at 0740, with full fuel. He then flew to Calexico International Airport. At Calexico, the pilot filed a VFR flight plan to Ryan Field and anticipated the arrival about 1130. En route to Ryan Field, the pilot stopped at Gila Bend Airport to rest. At 1030, the pilot departed Gila Bend. Approximately 6 nautical miles from Tucson International Airport (TUS), the decision was made to detour to Marana Northwest Regional Airport (AVQ), Marana, Arizona, to have breakfast and refuel. Suddently, the engine began to sputter and then resumed the normal rpm. The engine instruments were indicating normal operations. After contacting Tucson tower to declare an emergency, he turned toward Tucson International. The engine sputtered a second time and died. After an unsuccessful restart attempt, he established best glide airspeed. The pilot completed a soft field landing in a desert field, resulting in substantial damage to the nose gear, wing tips, and right side of the fuselage. In an interview with the Tucson Airport Police Department, the pilot stated that he could not make it to the airport because the airplane ran out of fuel. The officer noted that the airplane's left wing collided into a tree during the forced landing.