ACCORDING TO THE PLT, A CERT A&P MECHANIC, HE HAD FLOWN THE ACFT 1 HR SINCE LAST INSPECTION & EVERYTHING OPERATED NORMALLY. ON THE DAY OF THE ACCIDENT, HIS WIFE, ALSO A PLT, DEPARTED THEIR PRIVATE ARPT AT MERCER, PA ON A LOCAL FLT BUTLANDED AT GREENVILLE 15 MIN LATER BECAUSE OF A ROUGH RUNNING ENG. AFTER ARRIVING AT GREENVILLE, THE PLT REPLACED SEVERALOF THE FUEL INJECTION NOZZLES BECAUSE OF PREVIOUS PROBLEMS WITH THE NOZZLES STICKING DUE TO VARNISH DEPOSITS. THE PLT THEN TOOK OFF ON A LOCAL TEST HOP. AT ABOUT 100 FT AGL THE ENG BEGAN TO RUN ROUGH & LOSE POWER. HE MADE A TURN TO THE LEFT TO RETURN TO THE ARPT. DURING THE TURN THE LEFT WING STRUCK THE GROUND & THE ACFT CRASHED. SUBSEQUENT INVESTIGAITON REVEALED THAT THE INTERNAL MECHANISMS OF THE INJECTOR NOZZLES FROM CYLINDERS 2,3 & 4 WERE STRUCK IN THE CLOSED POSITION & WERE UNABLE TO PRODUCE ANY SPRAY OF FUEL.