TM-9-2350-311-20-1 Maintenance Manual for Volume 1 M109 Hull Download
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TM 9-2350-311-20-1 1-17 EQUIPMENT OPERATION AND DESCRIPTION — CONTINUED 1-17.2 Fuel System 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 (1) — provides additional fuel to the lower fuel tank (2). Filling of both fuel tanks takes place through the filler neck of the upper fuel tank. Lower fuel tank (2) — provides for fuel storage and for the return of unused fuel from the fuel return system (9). Electric fuel pumps (3) — activated by the MASTER switch on the instrument panel (M109A2/M109A3) or by an oil pressure switch (M109A4/M109A5), these pumps distribute fuel from the lower fuel tank (2) to the fuel distribution center (4). When engine is not operating, the electric fuel pumps, activated by the fuel prime switch on the instrument panel, pumps fuel from the primary fuel filter (5) to the secondary fuel filter (7). Fuel distribution center (4) — distributes fuel to the primary fuel filter (5). Primary fuel filter (5) — first filter from the fuel tank. Secondary fuel filter (6) — filters fuel a second time for additional impurities. Engine-driven fuel pump (7) — boosts fuel pressure and delivers fuel to engine (8). Engine (8) — bums fuel. Fuel return system (9) — distributes excess fuel back to either the lower fuel tank (2) or the flame heater system. 1-20