GA SMT INFLT ENGINE SHUTDOWN DUE FUEL EXHAUSTION IN ONE TANK. ACFT WAS BEING VECTORED FOR ILS APCH AND PLT ELECTED TO SHUT ENGINE DOWN; TO PREVENT SURGING AND ASSOCIATED CTL PROBLEM.

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PRIOR TO DEPARTING (MWH); I PREFLTED BY SMT. ON INSPECTING THE FUEL GAUGES IT APPEARED THAT THERE WAS 25 GALS OF FUEL IN EACH OF THE GAS TANKS. I THEN OPENED BOTH OF THE WING TANK FUEL FILLERS BUT; BECAUSE OF THE WING DIHEDRAL; IT WAS IMPOSSIBLE TO SEE ANY FUEL IN THE TANKS. (IN THE SMT; IT IS IMPOSSIBLE TO SEE ANY FUEL IN THE WINGS WHEN THE FUEL TANKS ARE 1/2 FULL OR LESS.) I DEPARTED ON AN IFR FLT PLAN TO HIO. THIS IS APPROX A 1 HR FLT. IN THE PDX AREA I HAD BEEN CLRED TO 4000' AND WAS BEING VECTORED ON A DOWNWIND APCH FOR THE ILS 12 APCH AT HIO. WHILE ON MY DOWNWIND; THE LEFT ENG SUDDENLY LOST PWR. THE ENG THEN BEGAN SEVERAL SURGES FROM NO PWR BACK TO NORMAL PWR; WHICH MADE DIRECTIONAL CTL VERY DIFFICULT. BECAUSE THE BULK OF MY FLT HAD BEEN CONDUCTED IN IMC CONDITIONS; I HAD BEEN CONSTANTLY MONITORING MY GAUGES DURING THE FLT. AS I APCHED PORTLAND I WAS CONCERNED ABOUT MY FUEL RESERVES; BUT BOTH OF MY FUEL GAUGES INDICATED THAT I WAS NOT YET INTO THE REQUIRED 45 MIN FUEL RESERVE. FROM THE ATIS I KNEW THAT CONDITIONS WERE A CEILING OF 2200' WITH 10 MI OF VIS; SO I WASN'T CONCERNED ABOUT HAVING TO SHOOT A LOW APCH. I NOTIFIED PORTLAND APCH OF THE LOSS OF PWR IN MY LEFT ENG. I DID NOT DECLARE AN EMER; BUT DID REQUEST PRIORITY HANDLING INTO HIO. BEING UNABLE TO STABILIZE PWR IN THE ENG; AND SINCE I WAS ABOUT TO ENTER MY BASE LEG FOR THE ILS INTERCEPT; I ELECTED TO SHUT DOWN THE LEFT ENG AND FEATHER THE PROP. I THEN PROCEEDED UNEVENTFULLY WITH MY LNDG AT HIO. AFTER LNDG AN EXAMINATION OF THE LEFT FUEL TANK REVEALED THAT IT WAS OUT OF FUEL. AN EXAMINATION OF THE RIGHT TANK ALSO REVEALED THAT IT WAS EXTREMELY LOW ON FUEL. I BELIEVE THAT I COMMITTED 2 INITIAL ERRORS. THE FIRST WAS IN POSSIBLY MISREADING THE AMOUNT OF FUEL IN THE TANKS FROM THE GAUGE. I BELIEVE THAT THE GAUGE SAID 25 GALS OF FUEL IN EACH TANK WHICH WOULD HAVE BEEN SUFFICIENT FOR MY FLT TO HIO WITH ADEQUATE IFR RESERVES. IN RETROSPECT; I NOW FEEL THAT THE GAUGES MIGHT HAVE INDICATED ONLY 15 GALS OF FUEL PER SIDE WHICH WOULD HAVE PUT ME AT HIO WITH NO RESERVES. THE SECOND MISTAKE IS MUCH HARDER TO CORRECT BECAUSE IT INVOLVES DEVISING SOME WAY TO MEASURE THE FUEL IN THE TANKS; WHICH IS IMPOSSIBLE TO SEE WHEN BELOW 1/2 FULL; DUE TO THE WING DIHEDRAL. I AM CURRENTLY EXPLORING SOME DIFFERENT ALTERNATIVES FOR PHYSICALLY MEASURING THE FUEL IN THE TANKS; BUT AS YET HAVE NOT COME UP WITH ANY RELIABLE METHOD. THE ONE THING OF PARAMOUNT IMPORTANCE THAT I HAVE LEARNED FROM THIS ENTIRE INCIDENT CONSISTS OF NOT RELYING ON THE FUEL GAUGES AND MAKING SURE THAT I HAVE MORE THAN ENOUGH FUEL ON BOARD AT ALL TIMES.