THE FUEL TANKS WERE TOPPED THE NIGHT BEFORE THE ACCIDENT & THE ACFT WAS LEFT OUTSIDE. DURING THE PREFLT, THE PLT DRAINED EACH FUEL TANK FOR ABOUT 5 SECONDS USING THE COCKPIT DRAIN BUT A CONTAINER WAS NOT USED. ENG RUNUP PRIOR TO DEPARTURE WAS NORMAL. AFTER ROTATION, ACFT YAWED TO THE LT. HE APPLIED RT RUDDER BUT THE ACFT COLLIDED WITH TREES, A POWERLINE, THEN THE GROUND. THERE WAS NO FIRE. FIRE DEPT PERSONNEL TURNED OFF THE FUEL SELECTORS WHICH WERE POSITIONED FROM EACH MAIN TANK TO ENG. FUEL TANKS WERE DRAINED & NO DETERMINATION COULD BE MADE AS TO WHETHER THERE WERE CONTAMINANTS. LT ENG GASCOLATOR WAS CLEAN BUT RT ENG GASCOLATOR CONTAINED SEDIMENT. EXAM OF THE LT ENG REVEALED THE LT MAG WAS NOT CORRECTLY TIMED TO THE ENG BUT THE RT MAG WAS. BOTH MAGNETOS WERE TESTED & OPERATED NORMALLY. THE FUEL SERVO, DISTRIBUTOR VALVE, NOZZLES & LINES WERE REMOVED FOR TESTING & OPERATED NORMALLY. NO DETERMINATION COULD BE MADE AS TO THE REASON FOR THE REPORTED LOSS OF ENG PWR FROM THE LT ENG.