Navistar MaxxForce 7 - Page 28

SECTION1–ENGINESYSTEMS
EngineDescription(cont.)
Thecamshaftissupportedbyvebushingspressedintothe
crankcase.Thecamshaftiscrankshaftdriven,andthrustis
controlledbyaplatemountedbehindtherearbulkhead.
Anopencrankcasebreathersystemdrawscrankcasevapors
throughabreatherelement.Thebreatherelementseparates
oilfromoilvapors,thenroutesbreatherairthroughanopen
breatheroutlettubeassemblyandreturnstheoiltothe
crankcasethroughapassageintherightvalvecover.
Crankshaft
Thecrankshaftissupportedbyvemainbearingswithforeand
aftthrustcontrolledattheupperhalfofthefourthmainbearing.
Twoconnectingrodsareattachedtoeachcrankshaftrodjournal
andareoffsettominimizevibration.Pistonpinsarefreeoating,
allowingthepinsfreelateralmovementwithintheconnectingrod
aswellasthepiston.Pistonpinsareheldinplacewithretaining
rings.
CylinderHeads
Thecylinderheadshavefourvalvespercylinder.Eachfuel
injectoriscentrallylocatedbetweenthefourvalvesanddirects
fueloverthepistonbowlforimprovedperformanceandreduced
emissions.
Theoverheadvalvetrainincludeshydraulicrollercamfollowers,
pushrods,rockerarms,andvalvebridgestoopenthedual
intakeandexhaustvalves.
ElectronicControlSystem
AnEngineControlModule(ECM)monitorsandcontrolsengine
performancetoensuremaximumperformanceandcompliance
withEPAemissionsrequirements.
Heavy-DutyOn-BoardDiagnostics(HD-OBD)isaU.S.
Governmentmandatedstandardforall2013andlaterClass4
andabovevehicleswithaGrossVehicleWeightRating(GVWR)
of14,001poundsormore.TheHD-OBDsystemmonitorsthe
engineandaftertreatmentsystemstoverifytheyareoperating
withinemissionslimits.Ifanemissionsfaultislogged,the
MalfunctionIndicatorLamp(MIL)willilluminateandoneormore
faultcodeswillbeset.
TheHD-OBDsystemoperatessimilarlytopreviouspowertrain
controlsystemsbystoringfaultcodesandturningontheMIL.If
theproblemthatcausedthefaultgoesaway,thecodewillclear
andtheMILwillgooutaftercertainoperatingconditionshave
beenmet.Thismaytakeseveraltimesoperatingthevehicle.
TheCrankshaftPosition(CKP)sensorandtheCamshaft
Position(CMP)sensorareusedbytheECMtocalculaterpm,
fueltiming,fuelquantity,anddurationoffuelinjection.
FuelSystem
Thehigh-pressurefuelsystemincludesaHigh-PressureFuel
Pump(HPFP),high-pressurecommonrails,andfuelinjectors.
TheECMelectronicallycontrolstheinjectors,allowingmultiple
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