MANIFOLD AIR INDUCTION HEATER SYSTEM

TM-9-2350-256-20 Carrier Cargo Tracked 6-Ton M548A1 (2350-01-096-9356) M548A3 2350-01-369-6081 Manual
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SECTION III: PRINCIPLES OF OPERATION TM 9-2350-256-20 1-15 MANIFOLD AIR INDUCTION HEATER SYSTEM NOTE Unless otherwise indicated, the following callouts are found in Figure 1-8. The left and right intake manifolds (6 and 9), which distribute supercharged air into each bank of cylinders, are equipped with electrically ignited intake manifold air heaters (2 and 8). The heaters are provided to facilitate engine starting during cold weather. The purge pump is operated to obtain 90 psi (621 kPa) in the manifold heater fuel lines. Operation of the heater switch on the purge pump handle energizes the manifold heater fuel inlet solenoid valve to allow fuel flow to the heater nozzle. The heater switch also energizes the high-tension coil creating an electrical spark in the manifold, thereby igniting the sprayed fuel. Continued operation of the purge pump is required to maintain fuel pressure and an effective spray pattern into the manifold. A leakoff line is provided to prevent nozzle fouling and is routed into the injector fuel return line. The fuel is burned in the intake manifold by the ignition of the heater spark plug, which flame-heats the incoming air. This flame-heated air and the products of combustion are fed directly into the cylinders. The purge pump line connects to a fuel check and pressure relief valve (14) and pressure regulator valve (see item 20, Figure 1-7) in the engine. The fuel check and pressure relief valve prevents purged fuel from returning to the tank or to the purge inlet line. The fuel check and pressure relief valve (14) ensures the necessary fuel pressure to operate the flame heater spray nozzles (5 and 10). A manifold heater fuel supply solenoid valve (7) and fuel return solenoid valve (16) close the flame heater fuel lines when the flame heater switch is off. The manifold heater fuel return solenoid valve (16) is located at the rear of the engine. The valve is energized at the same time the ignition unit and heater spark plugs are energized and acts as a check valve to prevent fuel returning from the injector pump and nozzles from entering the heater fuel tubes. 1 Left manifold heater ignition unit 2 Left manifold air heater 3 Spark plug 4 Ignition unit electrical lead 5 Manifold heater nozzle 6 Left intake manifold 7 Manifold heater fuel supply solenoid valve 8 Right manifold air heater 9 Right intake manifold 10 Manifold heater nozzle 11 Spark plug 12 Ignition unit electrical lead 13 Right manifold heater ignition unit 14 Fuel check and pressure relief valve 15 Manifold heater fuel filter 16 Manifold heater fuel return solenoid valve Figure 1-8. Manifold Air Induction Heater System 1-23

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