Incident Summary
A pilot reported that after approximately 1.7 hours of flight, the engine began to run rough. The pilot contacted the nearest control tower to report the problem while attempting to turn back to an airport he had just passed. After making a 180-degree turn, the engine died. Unsure he could make it to the airport without endangering people on the ground, the pilot opted to set the aircraft down in an empty field. The landing was uneventful, but during the landing roll the aircraft encountered a divot in the ground and nosed over onto its back.
Findings
After the aircraft was righted, an FAA inspector noted that the fuel filler cap on the right wing was missing. There were several blue stain streaks aft of the filler port extending to the trailing edge of the wing. Further investigation located the fuel filler cap in the run-up area where the pilot had last refueled. Examination of the fuel system found it to be intact, but only about 3 tablespoons of fuel were present in the fuel sump. No fuel was found in the main fuel lines leading to the injector when the boost pump was turned on.