TM-9-2350-311-10 M109 Operator's Manual for M109A2, M109A3, M109A4 and M109A5 Download
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TM 9-2350-311-10 1–14 EQUIPMENT 1–14.2 Fuel System OPERATION AND DESCRIPTION — CONTINUED The fuel system flow diagram shows the interaction between the electrical system and fuel system to determine the flow of fuel. a. b. c. d. e. f. g. h. i. UPPER FUEL TANK. The upper fuel tank (1) provides additional fuel to the lower fuel tank (2). Filling of both fuel tanks takes place through the filler neck (3) of the upper fuel tank. LOWER FUEL TANK, The lower fuel tank (2) provides for fuel storage and for the return of unused fuel from the fuel return system (4). ELECTRIC FUEL PUMPS. The electric fuel pumps (5) are activated by the MASTER switch on the instrument panel (M109A2/M109A3) or by an oil pressure switch (M109A4/M109A5). These electric fuel pumps distribute fuel from the lower fuel tank (2) to the fuel distribution center (6). When engine is not operating, the electrical fuel pumps, activated by the fuel prime switch on the driver’s fixed instrument panel, pumps fuel from the primary fuel filter (7) to the secondary fuel filter (8). FUEL DISTRIBUTION CENTER, The fuel distribution center (6) distributes fuel to the primary fuel filter (7). PRIMARY FUEL FILTER. The primary fuel filter (7) is the first filter from the upper fuel tank, ENGINE-DRIVEN FUEL PUMP. The engine-driven fuel pump (9) boosts fuel pressure and delivers fuel to the engine. SECONDARY FUEL FILTER. The secondary fuel filter (8) filters fuel a second time for additional impurities. ENGINE. The engine (Model 7083-7396) (10) or LHR engine (Model 7083-7391) (11) burns fuel, FUEL RETURN SYSTEM. The fuel return system (4) distributes excess fuel back to the lower fuel tank (2). 1-24