At about 14:36 PST, a Siai-Marchetti SF260 lost power while on approach to the Napa Airport and landed about 300 yards short of the runway. The pilot and passenger were not injured. The flight had originated in Phoenix at about 10:15 MST. The pilot said he was aware the airplane was low on fuel while he was approaching Napa, but he did not advise controllers of his fuel status. Engine power was lost while he was on the base leg of a standard traffic pattern.