A FRIEND WHO OBSERVED THE PLT PREFLIGHTING THE ACFT SAW HIM DRAIN FUEL FROM THE SUMPS TO CHECK FOR WATER. HOWEVER, HE DID NOT SEE THE PLT CHECK THE FUEL LEVEL IN THE TANKS. THE PLT TAXIED TO THE RWY, PERFORMED AN ENG RUN-UP & TOOK OFF. SHORTLY AFTER LIFT-OFF, WITNESSES NOTED A LOSS OF ENG POWER. THE ACFT THEN DESCENDED IN A LEFT TURN & COLLIDED WITH THE GROUND LESS THAN 1 MI FROM THE ARPT. AN EXAM OF THE ACFT DISCLOSED A TOTAL OF ABOUT 1 GAL OF FUEL ABOARD. APRX 1 GAL WAS FOUND IN THE LEFT MAIN & AUX TANKS. NO FUEL WAS FOUND IN THE RIGHT MAIN & AUX TANKS. THERE WAS NO EVIDENCE OF FUEL LEAKAGE FROM THE LEFT WING, BUT AN UNDETERMINED AMOUNT OF FUEL HAD LEAKED FROM THE RIGHT TANKS. THE LEFT FUEL SELECTOR WAS FOUND POSITIONED TO THE LEFT MAIN TANK; THE RIGHT SELECTOR WAS POSITIONED TO THE RIGHT AUX TANK. THE ACFT WAS PLACARDED FOR TAKEOFF BY USING THE MAIN TANKS ONLY. ME TOX CHECK SHOWED BLOOD/ALCOHOL LVL: 0.148%, VITREOUS/ALCOHOL LVL:0.003%; HOWEVER, FAA TESTS WERE NEGATIVE FOR ALCOHOL IN BLOOD & URINE; NH STATE TEST SHOWED LESS THAN 0.01% IN BLOOD.