TM 9--2815--247--34 0004 00--9 THEORY OF OPERATION -- CONTINUED 0004 00 1--16 MANIFOLD AIR INDUCTION AND HEATER SYSTEM -- CONTINUED MANIFOLD HEATER FUEL RETURN SOLENOID VALVE LEFT IGNITION UNIT RIGHT IGNITION UNIT MAIN FUEL BACKFLOW VALVE MANIFOLD HEATER FUEL INLET SOLENOID VALVE MANIFOLD HEATER FUEL FILTER RIGHT MANIFOLD AIR HEATER SOLENOID ELECTRICAL CONNECTION FUEL RETURN FROM FUEL INJECTOR NOZZLES IGNITION UNIT ELECTRICAL LEAD PURGE PUMP SOLENOID PURGE PUMP FUEL RETURN FROM FUEL METERING PUMP Figure 1--10. Manifold Air Induction Heater System Flow Diagram