TM 9--2350--292--20--1
0005 00--4
THEORY OF OPERATION -- CONTINUED
0005 00
FUEL SYSTEM
Three fuel tanks supply fuel to the engine, auxiliary power unit and the refuel system. Two tanks are adjacent to the
engine, one on either side and one forward of the bulkhead in the hydraulic compartment.
A system of four manually operated control valves (1) maintains fuel flow through the check valve (2) and directs
fuel to the engine and refueling systems. These valves are also used to drain the fuel tanks.
The fuel from the vehicle fuel tanks is supplied at a minimum pressure of 5 psi to the primary fuel filter (3), which is
mounted on the engine right front. Fuel flows through the main fuel check valve (fuel backflow valve) (4) to the en-
gine fuel pump (5) mounted on the front center of the engine. This is an engine--driven, gear--type pump; it boosts
fuel pressure to the fuel metering pump (6). A relief valve is incorporated in the pump as a pressure limiting safety
valve.
Fuel from the engine fuel pump (5) is filtered through the fuel/water separator filter (7) and passes into the fuel me-
tering pump (6), located in the engine V between the cooling fans. The metering pump (6) delivers metered quanti-
ties of fuel under high pressure to each cylinder. An integral governor, of the mechanical--centrifugal type, is used
to control fuel delivery as a function of engine speed. Engine shutoff is accomplished by a normally open solenoid
control unit in the metering pump (6).
Twelve stainless steel fuel lines (8) carry fuel under high pressure from the fuel metering pump (6) to the twelve fuel
injector nozzles (9) on the left and right banks of the engine. The nozzles (9) inject a fine spray of metered fuel un-
der pressure into each cylinder. Excess fuel is carried from the nozzles (9) through return tubes (10) and hoses
(11) on each cylinder bank to the fuel return system.
The engine fuel shutoff switch on the master control panel actuates the circuit to close the solenoid in the fuel injec-
tor pump (6). Closing the solenoid cuts off fuel from the metering pump (6) and stops the engine. The engine is
equipped with a manual fuel shutoff control (12) to stop the engine if the electric fuel shutoff should fail. A bleeder
pressure--relief valve (13) in the pump outlet maintains a constant fuel pressure by allowing any accumulated air
and excess fuel to return to the fuel tanks through the engine and fuel tank return tubes (10), check valve (14), re-
turn hoses (11) and control valves (1). Excess fuel is used to lubricate and cool the fuel metering pump (6). The
check valve (14) prevents a back flow of fuel into the metering pump (6) from the fuel return tubes (10) and hoses
(11) and prevents continued engine operation after the fuel shutoff valve is closed.
