Section 2Section 2
Fuel SystemFuel System
2 12 1THDC / THDCP 954 / 955 / 974 (Rev 06/03)THDC / THDCP 954 / 955 / 974 (Rev 06/03)
LLH H RRHH
FUEL / WATERFUEL / WATER
SEPARATORSEPARATOR
FILTERSFILTERS
FUEL FUEL
PUMPPUMP
FUELFUEL
SOLENOIDSOLENOID
FUELFUEL
TANKTANK
FUELFUEL
COOLERCOOLER
FUEL FLOWFUEL FLOW
INDICATES FUEL SUPPLYINDICATES FUEL SUPPLY
INDICAINDICATES TES FUEL FUEL RECOVERRECOVERYY
SUPPLYSUPPLY
LINELINE
RETURNRETURN
LINELINE
ENGINEENGINE
CYLINDERCYLINDER
HEADHEAD
IllustIllustration 2-ration 2-1. 1. Fuel SyFuel Systemstem
Introduction.Introduction. Fuel is drawn from the tank throughFuel is drawn from the tank through
the fuel / water separator filters by the fuel pump.the fuel / water separator filters by the fuel pump.
From here, the fuel is sent to the fuel injectors.From here, the fuel is sent to the fuel injectors.
Unused fuel is returned through the fuel coolerUnused fuel is returned through the fuel cooler
and into the fuel tank.and into the fuel tank.
Major ComponentsMajor Components(Illustration 2-1)(Illustration 2-1).. The fuelThe fuel
system consists of a fuel tank, two fuel / watersystem consists of a fuel tank, two fuel / water
separator filters, fuel pump, fuel solenoid valve,separator filters, fuel pump, fuel solenoid valve,
fuel cooler, fuel injectors and fuel lines.fuel cooler, fuel injectors and fuel lines.
Fuel Solenoid ValveFuel Solenoid Valve(Illustration 2-1)(Illustration 2-1).. The fuel The fuel
solenoid valve, located on the fuel pump itself,solenoid valve, located on the fuel pump itself,
controls the on / off flow of fuel to the fuel injec-controls the on / off flow of fuel to the fuel injec-
tors. tors. The fuel solenoiThe fuel solenoid valve is normd valve is normally clally closedosed
and requires a 12 VDC signal to energize the coil,and requires a 12 VDC signal to energize the coil,
shifting the sshifting the spool to the open state. pool to the open state. This allThis allowsows
the fuel to flow to the injector pump.the fuel to flow to the injector pump.
Adding FuelAdding Fuel(Illustration 2-3)(Illustration 2-3).. When adding die-When adding die-
sel fuel to the fuel tank, make sure the fuel strain-sel fuel to the fuel tank, make sure the fuel strain-
er is in the filler necer is in the filler neck and free of debris. k and free of debris. AddiAddingng
fuel with the strainer removed could lead to debrisfuel with the strainer removed could lead to debris
entering the fuel tank, resulting in poor engineentering the fuel tank, resulting in poor engine
performance.performance.
Fuel CoolerFuel Cooler(Illustration 2-1)(Illustration 2-1).. The fuel cooler,The fuel cooler,
located inside the radiator shroud, is forced-airlocated inside the radiator shroud, is forced-air
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