THE ACFT COLLIDED WITH A POWERLINE AND CRASHED AFTER THE ENGINE LOST POWER ON TAKEOFF. ACCORDING TO WITNESSES THE ACFT MADE A NORMAL TAKEOFF BUT DURING CLIMBOUT THE ENGINE BACKFIRED AND DARK SMOKE CAME OUT. THE ACFT TURNED LEFT THEN STEEPLY RIGHT BEFORE HITTING THE POWER LINE. THIS ACFT WAS FLOWN 3 TIMES IN 1982 AND TWICE PRIOR TO THE DAY OF THE ACC IN 1983. THE LAST TIME THE ACFT WAS REFUELED WAS IN SEPT, 1982. THE ACFT WAS PARKED OUTDOORS. THE GAS CAP IN THE WING SHOWED AREAS OF RUST AND CORROSION PREVENTING A TIGHT SEAL. MOISTURE COULD LEAK INTO THE FUEL TANK FROM RAIN AND MELTINGSNOW. ON 4/11/83 THE LEFT WING FUEL TANK WAS EXAMINED BY CUTTING INTO IT. THE BLADDER WAS SEVERELY WRINKLED ON THE BOTTOM. THE WRINKLING PRODUCED POCKETS LARGE ENOUGH TO TRAP ABOUT 1 GALLON OF WATER. THIS WATER WOULD NOT REACH THE DRAIN SUMP WITH THE ACFT IN A LEVEL PARKED POSITION. THE NTSB HAS MADE RECOMMENDATIONS TO FAA CONCERNING WATER IN FUEL AND EVALUATION OF BLADDER TYPE FUEL TANKS.