Narrative:

I was cruising at 12000 ft when I experienced a roughness from the engine. I declared an emergency with center and asked for immediate divert and vectors for an airport which was off of my left wing well within gliding distance of my aircraft. After I was given clearance to turn and I have initiated the turn I began my engine out checklist. The first item was to switch tanks. Upon switching tanks the roughness went away. I observed both of my fuel gauges reading 9 gallons in each tank. After an unremarkable landing and during taxi I observed my low fuel light for the right side tank illuminate which should indicate 3 gallons remaining; yet the gauge still read 9 gallons. After arriving at the FBO I inspected the right tank and saw that the level was very low. I had the fuel truck fill both tanks and recorded each and the right took 9 more than the left proving that it was empty. The left still had 9 gallons remaining. A mechanic on the field inspected the engine and preformed several full power run ups and did not find anything wrong with the engine. I believe that I experienced a failure of my right hand fuel tank sender and exhausted the fuel in that tank. Contributing factors were not using a fuel dip stick during preflight and not proving readings between the sight gages and the panel mounted fuel gauges. Corrective actions are to repair the fuel tank sender and use better fuel tracking practices in the future.

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Original NASA ASRS Text

Title: A M20K pilot declared an emergency and diverted to a nearby field when his engine began running rough. He found that the fuel tank supplying the engine had a faulty gauge and was empty when it indicated nine gallons.

Narrative: I was cruising at 12000 FT when I experienced a roughness from the engine. I declared an emergency with Center and asked for immediate divert and vectors for an airport which was off of my left wing well within gliding distance of my aircraft. After I was given clearance to turn and I have initiated the turn I began my engine out checklist. The first item was to switch tanks. Upon switching tanks the roughness went away. I observed both of my fuel gauges reading 9 gallons in each tank. After an unremarkable landing and during taxi I observed my low fuel light for the right side tank illuminate which should indicate 3 gallons remaining; yet the gauge still read 9 gallons. After arriving at the FBO I inspected the right tank and saw that the level was very low. I had the fuel truck fill both tanks and recorded each and the right took 9 more than the left proving that it was empty. The left still had 9 gallons remaining. A mechanic on the field inspected the engine and preformed several full power run ups and did not find anything wrong with the engine. I believe that I experienced a failure of my right hand fuel tank sender and exhausted the fuel in that tank. Contributing factors were not using a fuel dip stick during preflight and not proving readings between the sight gages and the panel mounted fuel gauges. Corrective actions are to repair the fuel tank sender and use better fuel tracking practices in the future.

Data retrieved from NASA's ASRS site as of April 2012 and automatically converted to unabbreviated mixed upper/lowercase text. This report is for informational purposes with no guarantee of accuracy. See NASA's ASRS site for official report.