What happened
The pilot departed with the nose fuel tank at full capacity. Approximately 15 minutes into the flight, the pilot observed that the fuel float indicator had dropped to one-third of a tank. Shortly thereafter, the indicator showed an empty reading. In response to the declining fuel indication, the pilot executed a precautionary landing in an open field.
During the landing roll through tall alfalfa, the airplane nosed over. The pilot was not injured during the event.
The investigation
An inspection of the aircraft's fuel system revealed that a wire had become bent approximately four inches above the float. This bent wire was creating drag against the cap, which resulted in an erroneous fuel quantity indication while the actual fuel level was lower than what was being displayed on the indicator.