What happened
The pilot did not perform any fuel consumption calculations prior to departing on the flight. Based on an estimate of having between 1 inch and 1 1/2 inches of fuel in both the left and right tanks, the pilot added 10 gallons of fuel to each tank. After flying to an intermediate stop to pick up a passenger, the pilot departed for the destination airport.
While leveled at 1,800 feet AGL, the engine began running rough. The pilot attempted to rectify the issue by switching fuel tanks and turning the boost pump to high, which temporarily smoothed out the engine. After the pilot turned the boost pump off, the engine began running rough again approximately three minutes later. Following unsuccessful attempts to resolve the engine roughness, a forced landing was executed in the only available landing area, resulting in the uninjured aircraft colliding with a fence post.
The investigation
An examination of the fuel system by the FAA determined that the fuel tanks were not ruptured. Investigators found only one pint of fuel remaining in the fuel system.