What was found
DURING A ROUTINE FLIGHT THE PILOT NOTED A FUEL SMELL DURING HEATER OPERATION. HE SHUT OFF THE HEATER AND RETURNED TO MAINTENANCE BASE. THE MECHANICS NOTED THAT THE HEATER FUEL PSI REGULATOR WAS LEAKING FROM DIAPHRAGM SEAL AREA. A NEW VALVE WAS INSTALLED, BUT FAILED AFTER 2 HRS OF OPERATION. A 2ND NEW VALVE WAS INSTALLED AND WAS FOUND TO LEAK FROM DIAPHRAGM AREA AFTER A FEW HOURS OF OPERATION. THE THIRD VALVE WORKS NORMALLY. NO LEAKS WERE FOUND.