电喷发动机燃油供给与喷射控制-EFI-fuel-delivery-&-injection-contr

OverviewoftheFuelDeliverySystemThefueldeliverysystemincorporatesthefollowingcomponents:1)Fueltank(withevaporativeemissionscontrols)2)Fuelpump3)Fuelpipeandinlinefilter4)Fueldeliverypipe(fuelrail)5)Pulsationdamper(manyengines)6)Fuelinjectors7)Coldstartinjector(mostengines)8)Fuelpressureregulator9)FuelreturnpipeFuelispumpedfromthetankbyanelectricfuelpump,whichiscontrolledbythecircuitopeningrelay.Fuelflowsthroughthefuelfiltertothefuelrail(fueldeliverypipe)anduptothepressureregulatorwhereitisheldunderpressure.Thepressureregulatormaintainsfuelpressureintherailataspecifiedvalueaboveintakemanifoldpressure.Thismaintainsaconstantpressuredropacrossthefuelinjectorsregardlessofengineload.Fuelinexcessofthatconsumedbyengineoperationisreturnedtothetankbywayofthefuelreturnline.Apulsationdamper,mountedtothefuelrail,isusedonsomeenginestoabsorbpressurevariationsinthefuelrailduetoinjectorsopeningandclosing.Thefuelinjectors,whichdirectlycontrolfuelmeteringtotheintakemanifold,arepulsedbytheECU.TheECUcompletestheinjectorgroundcircuitforacalculatedamountoftimereferredtoasinjectiondurationorinjectionpulsewidth.TheECUdetermineswhichair/fuelratiotheenginerunsatbaseduponengineconditionsmonitoredbyinputsensorsandaprogramstoredinitsmemory.Duringcoldenginestarting,manyenginesincorporateacoldstartinjectordesignedtoimprovestartabilitybelowaspecifiedcoolanttemperature.EFI#3-FUELDELIVERY&INJECTIONCONTROLPage1©ToyotaMotorSales,U.S.A.,Inc.AllRightsReserved.FuelDeliveryandInjectionControlComponentsFuelPumpsOvertheyears,ToyotahasusedtwotypesofelectricfuelpumpsonEFIsystems.TheearlyConventionalEFIsystemusedanexternallymountedin-linepump.Theserollercellpumpsincorporateanintegralpressurepulsedamperorsilencerdesignedtosmoothoutpressurepulsesandprovidequietoperation.EFI#3-FUELDELIVERY&INJECTIONCONTROLPage2©ToyotaMotorSales,U.S.A.,Inc.AllRightsReserved.Latermodelproductionenginesutilizeanin-tankpumpintegratedwiththefuelsenderunit.Theseturbinepumpsoperatewithlessdischargepulsationandrunquieterthanthein-linevariety.In-tankpumpscanbeservicedbyremovingthefuelsenderunitfromthetank.Makesurethatthepumpcouplinghoseisingoodconditionpriortoreplacingthepump.Bothpumpssharemanyfeatures.Theyarereferredtoaswetpumpsbecausetheelectricmotoroperatesimmersedinfuel.Passingfuelthroughthepumpmotoraidsincoolingandlubrication.Anoutletcheckvalveisincorporatedinthedischargeoutlettomaintainresidualorrestpressurewhentheengineisturnedoff.Thisreducesthepossibilityofvapor-lockandimprovesstartingcharacteristics.Apressurereliefvalveisusedtopreventover-pressureandpotentialfuelleakageintheeventthatpressureorreturnlinesbecomerestricted.EFI#3-FUELDELIVERY&INJECTIONCONTROLPage3©ToyotaMotorSales,U.S.A.,Inc.AllRightsReserved.FuelPumpElectricalControlsandCircuitOpeningRelayCircuitOpeningRelayCircuitsTherearethreetypesoffuelpumpcontrolcircuitsusedonToyota'sEFIengines.Onetypeofcontrol,AsecondtypeoffuelpumpcontrolusestheECUtocontrolcircuitopeningrelayrunwindingcurrent.UsedonenginesequippedwithDtypeEFIandonthe7M-GTE,whichusesaKarmanvortexairflowmeter,thisusedexclusivelywithLtypeinjection,utilizestheairflowmeterFccontacttocompletethecircuitopeningrelayrunwindingground.Thisisasafetyfeaturewhichpreventsthefuelpumpfromoperatingwhentheengineisnotrunning.safetyfeaturepreventsfuelpumpoperationwhenevertheECUfailstoseeanNe(enginerpm)signal.Undertheseconditions,theECUremovesgroundfromthecircuitopeningrelayrunwinding.EFI#3-FUELDELIVERY&INJECTIONCONTROLPage4©ToyotaMotorSales,U.S.A.,Inc.AllRightsReserved.FuelPumpSpeedControlThethirdtypeoffuelpumpcontrolcircuitutilizesatwo-speedpumpelectricalcircuit.Dependinguponengine,thecircuitopeningrelaymaybedrivenbytheECUorbytheairflowmeterFccontact.Pumpcurrent,however,issuppliedeitherthroughacurrentlimitingresistorordirectlytothepumpdependingonengineload,rpmandstatusoftheSTAsignal.Whentheengineiscranked,oroperatedathighspeedand/orheavyload,theECUturnsoffTR1,closingcontactAoftheFuelPumpControlRelay.Thisallowscurrenttoflowdirectlytothefuelpump,causingittorunathighspeed.Underallotheroperatingconditions,theECUturnsonTR1,whichenergizestheFuelPumpControlRelay.ThisclosesrelaycontactBandforcescurrenttoflowthroughtheresistor,causingthepumptorunatlowspeed.TheFuelPumpSpeedControlsystemisdesignedtoreduceelectricaldemandandpumpwearwhenfueldemandislowwhiledeliveringadequatefuelvolumewhendemandishigh.EFI#3-FUELDELIVERY&INJECTIONCONTROLPage5©ToyotaMotorSales,U.S.A.,Inc.AllRightsReserved.FuelPumpTestTerminalsTofacilitatetestingandallowpumpoperationindependentoftheairflowmeterorECUcontrol,allenginesutilizeafuelpumptestconnector.Therearetwobasictypesoffuelpumptestcircuits.MostlatemodelTCCSenginesuseanFptestterminallocatedinthecheckconnector.Withtheignitionswitchon,jumpering+BtotheFpterminalsendscurrent-directlytothefuelpump.Earlierenginesuseajumperconnectorreferredtoasa2Pfuelpumpcheckconnector.Thisconnector,whenjumpered,suppliesgroundforthecircuitopeningrelayrunwinding,allowingittooperateindependentlyoftheairflowmeterFccontact.EFI#3-FUELDELIVERY&INJECTIONCONTROLPage6©ToyotaMotorSales,U.S.A.,