As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT EXPERIENCED A LOSS OF ENGINE POWER WHILE IN FLIGHT NEAR AMALGA, UTAH. THE PILOT ELECTED TO MAKE A PRECAUTIONARY LANDING IN A FIELD. THE CAUSE OF THE ENGINE POWER ISSUE WAS DETERMINED TO BE A VENTED FUEL CAP THAT WAS NOT VENTING PROPERLY. THE IMPROPER VENTING ALLOWED A VACUUM TO DEVELOP IN THE FUEL TANK, WHICH RESTRICTED FUEL FLOW TO THE ENGINE. AS CORRECTIVE ACTION, BOTH FUEL CAPS WERE REPLACED