EMISSION CONTROLS-EXHAUST SYSTEMS Page Emission Controls 4A-1 Page Exhaust Systems 4A-36 EMISSION CONTROLS Air Guard System Catalytic Converter EGR System Emission Components Emission Control Maintenance Engine Modifications Fuel Tank Vapor Emission Control System Page 4A-7 PCV System 4A-16 Service Diagnosis Guide 4A-11 Specifications 4A-40 TAC System 4A-27 TCS System 4A-1O Tuneup Specifications 4A-1 7 VTM System GENERAL Emission control systems are required to meet exist ing standards for exhaust, crankcase, and raw fuel va por emissions. The systems control emission of hydrocarbons, carbon monoxide, and oxides of nitrogen at the levels specified by Federal or Ca]ifornia standards. Federal Emission Standards and the standards which apply in California differ. This necessitates a number of differences between emission control systems on ye- hides built for sale in California and in the remaining 49 states. Emission control system usage varies in re]ation to engine, transmission, and series application. The Emis sion Control Systems Application Chart at the end of this section may be used to determine the current sys tem usage for any particular vehicle. This section outlines service procedures for a]] Jeep Emission Control Systems. Tuneup specifications and procedures as prescribed by the U.S. Emission Control Services Maintenance Chart are also included. Service Diagnosis The following table lists causes of service problems in descending order of probability. It is more likely a problem results from the first listed ‘possible cause" than the tenth, for instance. However, visual examination often leads directly to the correct solution and all service procedures should begin with a careful look at any suspected part or assembly. Condition Possible Cause Correction 1 Binding linkage, choke valve or choke piston. 2 Initial choke valve setting inc orrect. 3 Restricted choke vacuum and hot air passages or disconnected vacuum hose. 4 Improper fuell level. 5 Dirty, worn or faulty needle valve and seat. 1 Repair as necessary. 2 Adjust initial choke valve correctly. 3 Clean passages or connect vacuum hose. 4 Adjust float level. 4A-1 Page 4A-20 4A-1 4A-37 4A-21 4A-24 4A-38 4A-23 HARD STARTING ENGINE CRANKS NORMALLY 5 Repair as necessary. 70494A
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EMISSION CONTROLS-EXHAUST SYSTEMS
PageEmission Controls 4A-1
PageExhaust Systems 4A-36
EMISSION CONTROLS
Air Guard SystemCatalytic ConverterEGR SystemEmission ComponentsEmission Control MaintenanceEngine ModificationsFuel Tank Vapor Emission Control System
Page4A-7 PCV System
4A-16 Service Diagnosis Guide4A-11 Specifications4A-40 TAC System4A-27 TCS System4A-1O Tuneup Specifications4A-1 7 VTM System
GENERAL
Emissioncontrol systemsare required to meet existing standardsfor exhaust,crankcase,and raw fuel vapor emissions. The systems control emission ofhydrocarbons,carbon monoxide,and oxides of nitrogenat the levels specified by Federal or Ca]iforniastandards.
FederalEmission Standardsand the standardswhichapply in California differ. This necessitatesa numberofdifferences between emission control systems on ye-
hidesbuilt for salein Californiaand in theremaining49states.
Emission control systemusagevaries in re]ation toengine, transmission,and seriesapplication.The Emission Control SystemsApplication Chart at the end ofthis section may be usedto determinethe current system usagefor any particular vehicle.
This sectionoutlines service proceduresfor a]] JeepEmission Control Systems.Tuneup specificationsandproceduresas prescribedby the U.S. Emission ControlServicesMaintenanceChartarealso included.
Service DiagnosisThe following table lists causes of service problems in descending order of probability. It is more likely a problem results from the first listed ‘possiblecause" than the tenth, for instance.
However, visual examination often leads directly to the correct solution and all service procedures should begin with a careful look at anysuspected part or assembly.
Condition PossibleCause Correction
1 Binding linkage, choke valve orchoke piston.
2 Initial chokevalvesettingincorrect.
3 Restrictedchokevacuumandhot air passagesor disconnectedvacuumhose.
Page PageAir Injection Manifolds and Tubes 4A-1O Diverter 4A-9Air Pump 4A-7 General 4A-7
GENERALThis systemincorporatesa belt driven air pump, di
verterbypassvalve, air injection manifolds and connectinghosesfig. 4A-1 and 4A-2.
Air is dischargedfrom the air pump to the divertervalve which directsit to the air distribution manifoldsor dumpsit through a bypassport, dependingon engineoperatingconditions.Air pressurein this systemis keptto approximately5 psi by a relief valve incorpo:ratedinthe divertervalve.
Air is routed through the air injection manifold intothe engineexhaustports. The air mixes with hot unburnedexhaustproducts and causesa further burningof the mixture, reducinghydrocarbonand carbonmonoxide emissionsto the atmosphere.
AIR PUMPThe air pumpusedfor V-8 andsix-cylinderenginesis
the same. A pump with a smaller diameterpulley isusedon V-8 engineswith altitude compensation.Themajor componentsof the air pump areenclosedin a die-cast aluminum housing. A filter fan assembly,rotorshaftanddrive hub arevisible on the pumpexterior fig.
Fig. 4A-2 Air-Guard System-V-8
HOUSING
AJ42006
VACUUM SENSINGLINE TO MANIFOLDVACUUM
DIVE RTER VALVE-TO-AIR INJECTION
4A-3.
HOSE DIVERTERVALVE-TO-AIRINJECTION MANIFOLD
AIR INJECTIONMANI FOLD
REAR COVER
‘VVENT HOLEDO NOT OIL
.
Al R PUMP-TODIVERTER VALVEHOSE
/43040
rROTOR SHAFT ANDDRtVE HUB
42007
Fig. 4A-1 Air-Guard System-SIx-Cyiinder Fig. 4A-3 Air Pump
4A-8 EMISSIONS CONTROLS - EXHAUST SYSTEMS
The pump is designedfor long life and is serviceableonly by replacement.It is not recommendedthat therearhousingcoverbe removedfor any reason,sincetheinternalcomponentsof the pump arenot serviceable.
The aluminum housing has cavities for air intake,compressionand exhaustand a bore for mounting thefront bearing.The housingalso includescastmeteringareasthat reducethe noise of intake and compression.Mounting bossesare locatedon the housingexterior.
The front bearingsupportsthe rotor shaft. The bearing is securedin position by plastic, injected aroundgroovesin the housingandbearingouter race.
The rearcoversupportsthe vanepivot pin, rearbearing raceand exhausttube.Dowel pins pressedinto thehousingcorrectly position the end cover which is fastenedby four bolts.
The rotor positions and drives the two vanes. Astamped steel liner supports carbon shoes and shoespringswhich sealthe vanesand rotor. The two plasticvanesare moldedto hubswhich support bearingsthatrotateon the pivot pin. The pulley drive hub is pressedon the rotor shaft,and bolt holes in the hub provideforattachmentof a pulley.
The pump vanesare located 180 degressapart androtate around the pivot pin which is located on thecenterlineof the pump housing.The rotor which drivesthevanesrotatesoff the centerlineof thepumphousingfig. 4A-4. This createschangesin the distancebetweenthe outsideof the rotor and the inner wall of the pumphousings during rotor rotation. As the leading vanemovespastthe intakeopening,it is movingfrom asmallareato a largeareadefinedby the rotor-to-pumphousing clearance.This forms a vacuum which draws airinto the pump. As the vanesand rotor continueto rotate,the trailing vanepassesthe intakeandtrapsthe airbetweenthe vanes.The vanesandrotor move into smallareaandtheentrappedair beginsto be compressed.Thecompressioncontinuesuntil the leadingvanepassestheexhaustopeningwherethe compressedair passesout ofthe pumpandon to the restof the Air GuardSystem.
VANEVANE
ROTOR
fSEALS
ROTATION
AJ42008
Air Pump DiagnosisThe air pump is not completelynoiseless.Undernor
mal conditions, noise rises in pitch as enginespeedincreases.Allow for normal break-in wear of the pumpprior to replacementfor excessivenoise.
First checkthedrive belt tensionandtightenasspecified. Do not pry on the aluminum housing.Checkhosesto be sure they are properlyconnectedandare in goodcondition andcheck that the pump mountingbracketissecurelyfastened.
Air pump noise can be confusedwith other enginenoise.On a noise complaint, first removethe drive beltand check the pump to make sure it is operative. Aseized pump will not rotate and the noise could becausedby belt slippage.
A chirping or squeakingnoise probably originatesfrom vanerub in the housingbore and is noticeableatlow speedintermittently. Vane chirping is often eliminated at increasedpump speeds, or with additionalwear-in time.
Bearingnoise is easilydistinguishedfrom vanechirping. It is a rolling soundnoticeableat all speeds.It doesnot necessarilyindicatebearingfailure. If bearingnoisereachesan objectionablelevel at certain speeds,thepumpmay haveto bereplaced.
Failureof a rearbearingis identified by a continuousknockingnoiseandreplacementof the pumpis required.
If it is determinedthat the air pumpis not deliveringair determinepresenceof airflow by removing an exhausthose,the pump mustbe replaced.
NOTE: Thepumpis equippedwith a centrifugal fan-type air filter, located behind the drive pulley. In theeventthat the engineorunderhoodcompartmentis to becleanedwith steamor high-pressuredetergent,thefiltershould be maskedoff to preventliquidsfrom enteringthe pump.
Service PrecautionsThe following is a list of serviceprecautionsto prevent
damageto the air pump.DO NOT:* Attempt to prevent pulley from rotating by inserting tools into the centrifugal filter fan.
* Operate engine with pump belt removed or disconnectedexceptfor noisediagnosis.
* Attempt to lubricate.* Cleancentrifugalfilter.* Disassemblepumpor removerearcover.* Exceed20 foot-poundstorqueon mountingbolts.* Pry on aluminumhousingto adjustbelt tension.* Clamppumpin vise.
Removal-Six-cylInder1 Disconnectair pump outputhoseat backof air
pump.
vu
PUMP
CENTERLINE OF PUMP BOREAND AXIS OF VANE ROTATION
SEALS
Fig. 4A-4 AIr Pump Operation 2 Loosenadjustmentbolt andremovedrivebelt.
EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-9
3 Remove front mount bracket-to-engineattaching bolts.
4 Remove rearmount bracket-to-pumpattachingbolts.
5 Loosen rear mount bracket-to-powersteeringattachingbolts.
6 Pull pumpdown andforwardto remove.
Installation-Six-Cylinder1 Positionpump and install rear mount bracket-
to-pumpattachingbolts.2 Install front mountbracket-to-engineattaching
bolts.3 Tighten attachingbolts to specifiedtorque.4 Adjust power steeringdrive belt to specified
tension.5 Connectair pumpoutputhoseto backof pump.6 Adjust air pumpdrive belt to specified tension.
Removal-V-81 Disconnectair pumpoutputhoseat pump.2 Loosen mount bracket-to-pump attaching
screwsandremovedrive belt.3 Remove mount bracket-to-pump attaching
bolts.4 Removepump.
Installation-V-81 Positionpump at mounting locationand install
mountbracket-to-pumpattachingbolts do not tighten.2 Install drive belt and adjust to the specified
tension.3 Tighten mounting bolts and adjusting strap
screwto 20 foot-poundstorque.
NOTE: If air pump is driven by the air conditioningbelt, adjust the belt to the tensiovspecifiedfor the airconditioning belt. Pry only against the cast iron coverwhen adjusting the belt. Do not pry on the aluminumhousing.
DI VENTER BYPASS VALVEA divertervalve is usedin all Air Guardapplications.
The valvesfor V-8 andsix-cylinderenginesdiffer only inthe numberof outlets. The V-8 diverter valve has twooutletsand the six-cylinderdiverter valve hasonly one.The valve momentarily diverts air pump output fromreachingthe exhaustduring rapid decelerationandactsas a pressurereleasewhenair pump outputis excessive.An internalsilenceris incorporatedin the diverterhousing to muffle the airflow.
In a rapid decelerationcondition, high intake manifold vacuumis appliedto thediaphragmin the diverter.When the vacuum signal is 20 inches of mercury ormore, the spring tensionof the diaphragmis overcome.
This moves the meteringvalve down againstits upperseat and away from its lower seat, forcing air pumpoutput to vent to atmospherefig. 4A-5. Air pumpoutput is divertedonly momentarilybecauseof a bleedholein the diaphragm.This hole allows vacuumto quicklyequalize on both sides of the diaphragmand the diaphragmspring returnsthe meteringvalve to its normalposition.
If the air pump developsexcessiveoutput pressure,this pressurewill overcomethe diaphragmspring tension, pushing the metering valve down and ventingpump output pressureto the atmosphere.When pumpoutput pressurereturnsto normal, the meteringvalvewill move up andaway from the upperseatand againstthe lower seat, returning to its normal open position,allowing air pump pressureto flow to the exhaustmanifolds.
Diverter Test
Fig. 4A-5 Diverter Vaive
VACUUMSENSINGINLET
INLETFROMAIRPUMP
A50277
1 Startengineandlet idle.2 Checkdiverter vents.Little or no air shouldflow
from vents.3 .Accelerateengineto 2000 to 3000 rpm and rap
idly close throttle. A strongflow of air shouldpassfromthe diverter vents for approximately 5 seconds.Thehigh-flow diverter usedon someenginesshouldvent forapproximately3 seconds.If air doesnot flow or if backfire occurs,makecertain vacuumsensingline has vacuumandis not leaking.
NOTE: The diverter valve diverts air pump outputwhen 20 inches of Hg or more is applied at vacuumsensingline orpumpoutputexceeds5 psi 8 psi on someniodels.
4 Slowly accelerateengine.Between2500and3500rpm, air shouldbegin to flow from diverter vents.
Diverter ReplacementThe diverter valve is not serviceableand must be
replacedif defective.The valve is attachedto a bracketor suspendedby the hosesbetweenthe air pumpandairinjection manifolds fig. 4A-1 and 4A-2. Removal involves disconnectingthe hosesand the vacuumsensingline and bracket clamp, if equipped. Installation involves reconnectingthe hosesand vacuumline and attachingthe bracketclamp, if equipped.
AIR INJECTION MANIFOLDSThe air injection manifolds are constructedof cold
rolled steel with a zinc plating and distributeair fromthe pumpto the exhaustports.
A check valve, incorporatinga stainlesssteel springplunger and an asbestosseat, is integral with the airinjection manifold. Its function is to preventthe reverseflow of exhaustgasesto the pumpduring pump failureor diverter valve bypassoperation.Reverseflow woulddamagetheair pumpandconnectinghoses.
The distribution tubes of the air injection manifoldare connecteddirectly to the exhaustmanifolds. Thehollow attaching screws conduct airflow into the exhaust manifolds.Air distribution tubesare usedfor allcylindersexceptNo. 7 on V-8 engines.
NOTE: Someinterferenceto removalmay be encountereddue to carbon buildup on thescrews.
3 Removeair injection manifold.4 Remove sealing gaskets from
manifold.
ENGINE MODIFICATIONS
The design of certain engine componentsis directlyrelated to emission standards.The operationof suchitems as the camshaft,carburetor,ignition distributorand cylinder head affects the amount of emissions.
Therefore, the correct combination of engine components, as prescribed by government certification,must be used in service.Refer to the appropriatesections of this manual for servicingthesecomponents.
vu
NOTE: Someresistance to removal may be encountereddue to carbon build-up on screws.
3 Removeair injection manifold.
1 Assembleair injection manifold and screws toexhaust manifold. Tighten screws to 20 foot-poundstorque.
2 Connectair deliveryhoseto checkvalve.
air injection
lnstallation-V-81 Install air injection manifold using a replace
ment sealinggasketat eitherside of eachopening.2 Install screws to exhaust manifold. Tighten
Check Valve TestTo check the air injection manifold valve for proper
operation,disconnecttheair supply hoseat the injectionmanifold. With the engine running above idle speed,listen and feel for exhaustleakageat the checkvalve. Aslight leak is normal.
all Jeepsreduces the formation of oxides of nitrogenNOx by introducing a meteredamountof exhaustgasinto the combustionchambers.Exhaustgasis inert,willnot burn, and thereforecombustiontemperaturesarereduced.Feweroxidesof nitrogenareproducedat lowercombustiontemperatures.
Jeepvehicles for 1977 use three different types ofEGR systemsfig. 4A-6, 4A-7 and 4A-8. The EGR system with no back-pressure sensor is used o:n all 49-stateCherokee,Wagoneerand Truck models.The EGRsystemwith integral back-pressuresensor is usedonall California Cherokee,Wagoneer and Truck modelsandall CJ modelsexceptCalifornia304 V-8 with manualtransmission.The EGR systemwith external, non-integral back-pressure sensor is usedon California CJmodelswith 304 V-8 and manualtransmission.
The EGR CTO switch preventsEGR action until engine temperaturereachesa presetlevl, and the back-pressuresensorpermits EGR action only at increasedengineloads, improvingdriveability.
The EGR valve mountson a machinedsurfaceat therearof the intake manifold on V-8 enginesand on theside of the intake manifold on six-cylinder engines.When the separateback-pressuresensor is used, theEGR valve mountson the spacerwhich is an integral
vi
EXHAUST BACKPRESSURE SENSOR
EGR VALVEBACK-PR ESSURESENSOR INTEGRALON MOST MODELS
CARBURETOR EGR PORT
INNERS-PORT
FRONT
CTO
Fig. 4A-6 EGR System-Six-Cylinder-Typical
4A-12 EMISSIONS CONTROLS - EXHAUST SYSTEMS
part of the back-pressuresensor.Exhaustgasis drawnfrom the exhaustcrossoverpassagein V-8 engines,froman areanearthe heatriser in six-cylinderengines.
EGR Valve without Integral Back-Pressure SensorEGR valves are calibratedby the use of differently
shapedpintles fig. 4A-9. The valve is normally heldclosedby a spring locatedabovethe diaphragmfig. 4A-10. The valve openswhensufficient vacuum is appliedthroughhosesconnectingthe CTO switch andthe back-pressuresensorif usedto the EGRvacuumport at thecarburetor.
When vacuumovercomesthe diaphragmspring pressure, a pintle within the valve is lifted off its seatandexhaustgas,which reachesthe EGRvalve throughspecial passages,is meteredinto the intakemanifold.
DIAPHRAGMSPRING
DIAPHRAGM.
PINTLESEAT
Fig. 4A-9 EGR Valve Pintles
TO INTAKE UPORT
Fig. 4A-10 EGR Vaive without Back-Pressure Sensor
EGR Valve with Integral Back-Pressure Sensor
A42013
vu
different diaphragmspring loads and flow control orifices. The unit combinesthe functions of the EGR valveand back-pressuretransducerinto a single component.A restrictor plate is not required.
Refer to figure 4A-11. The flow recirculation of exhaust gas is controlled by a movablepintle. In the relaxed position, spring pressureholds the pintle againstits seat,confining exhaustgasesto the exhaustmanifold. Carburetorvacuum is availableat the powerdiaphragm to pull the pintle from its seat. This cannothappenwhile the vacuumbleedvalve in the powerdiaphragmis open.
70421
Fig. 4A-1 1 EGR Valve with integral Back-Pressure Sensor
Exhaust gas exerts pressureback-pressureinsidethe exhaustmanifold wheneverthe engineis running.This pressureis conductedthrough the hollow pintlesteminto the control diaphragmchamber.If this pressure is great enough to overcomecontrol spring pressure, the control diaphragmis moved againstthe bleedvalve. Full vacuum is now applied to the power diaphragmandthe pintle moves.EGR now begins.If back-
pressure drops sufficiently, the control diaphragmmovesaway from the bleedvalve. Thepowerdiaphragmagain relaxesandEGR stops.
Systempressureremainsconstant,within the rangeof the unit. Recirculationis a function of the exhaustmanifold back-pressurelevel. EGR is dependent onback-pressureandis a fixed percentageof the incoming
BLEEDVALVE
VACUUM
PINTLES AJ4201 2
FROM CARBURETORPORTED VACUUMSOURCE
CCONTROLFLOW AREA
0 FROM EXHAUSTPORT
Calibration is accomplishedby the selective use of charge.
V. EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-13
EGR Valve Test
Valve Opening TestWith
rapidlyopeneddefinitediaphragm.
If the diaphragmdoesnot move, the probablecausesare: faulty vacuum signal to EGR, defective E;R diaphragmor defectivehack-pressuresensordiaphragm,ifequipped.Check vacuumlines for leaks.
Valve Closing Test
With the engineat operatingtemperatureand curbidle, manually depressthe EGR valve diaphragm.Thisshould cause an immediate engine speed d:rop, indicating that the EGR valve had beenproperlycuttingoff the flow of exhaustgas at idle.
If thereis no changein engine rpm and the engineisidling properly, exhaustgasesdo not reach the combustion chamber.The probabledifficulty is a pluggedpassage between the EGR valve and the intakemanifold.
If the engineidles poorly and rpm is not greatly affected by compressingthe EGR diaphragm,the EGRvalve is not closingoff the flow of exhaustgases.Thereis a fault in the hoses,hoseroutingsor the valve itself.
EGR Valve Replacement
Removal
1 On V-8 engines,removeair cleanerassembly.2 Disconnectvacuumhoses.3 Removetwo retainingbolts from manifold.4 RemoveEGR valve, gasket,spacerand attached
exhaustback-pressuresensorassemblyif used,restrictor plateand its gasketsif used.
5 Clean EGR pintle if required refer to EGRValve Maintenance.
6 Discard used gaskets and clean all matingsurfaces.
Installation
1 Install restrictor plate if used between twogasketsand install spacerif used, EGR gasket, andEGR valve.
2 Install retaining bolts and tighten to 13 foot-poundstorque.
3 Connect vacuum lines and install air cleanerassemblyif removed.
NOTE: The non-integral exhaustback-pressureassembig, /f. used, should extend toward the left side on V-8engines. The stainless steel rest rictor plate is calibrated
.toi the engine and exhaustsystem.foundon that vehicle.Always replace the same restrictor plate originallyiiis tailed.
EGR Valve Maintenance-Cherokoe-Wagoneer-TruckRemoveall leador carbondepositsfrom the stainless
steel metering pintle of the valve using a wire brush.After cleaning,depressthe diaphragm,capthe vacuuminlet, and repeatedlyopen the EGR valve manually bypressingdown on the diaphragmand releasing:Pintleshould[ remain retracted;if it doesnot, diaphragmhasaleak andvalve mustbe replaced.
On six-cylinder engines,lead or carbon depositswillbuild most rapidly in the exhaustgasdischargepassageupper hole. If the depositscannotbe removedwith aspiral-type wire brush, a 9/16-inch drill may be used.Coatthe tip of the drill with heavygreaseand usepliersVise-Grip to rotate the bit in the dischargepassage.
EGR CTO SWITCHThe EGRCTO switch is locatedat the coolantpassage
of the intakemanifold adjacentto the oil filler tube onV-8 engines,and at the left side of the cylinderblock onsix-cylinderengines.The inner port S connectsby hoseto the EGR port at the carburetor,the outer port Econnectsto the exhaustback-pressuresensor,when thevehicle is so equipped,or to the EGR valve.
When coolant temperatureis below the rating of theCTO switch thereis no vacuumsignalto the EGR system. The EGR CTO switch on the JeepCJ modelsopensat 115°Fand has a black body or a black paint dab.Allother Jeepmodels have an 160°F CTO switch with ayellow body or yellow paint dab.
EGR CTO Test
NOTE: Engine coolant temperaturemust be below100°F.
1 Check vacuumlines for leaks and correctroutings fig. 4A-6, 4A-7 and4A-8.
2 Disconnectvacuumline at back-pressuresensorif equippedor at the EGR valve, and connectline to avacuumgauge.
3 Operateengineat 1500 rpm. No vacuumshouldbe indicated on gauge. If vacuumis indicated, replaceEGR CTO switch.
4 Idle engine until coolant temperatureexceeds115°F black color code or 160°F yellow color code.Thetemperaturegaugeneedleis abouthalfway betweenthe cold mark and the beginningof the bandat 115°Fandaboutat the beginningof the bandat 160°F.
engineat operatingtemperatureand curb idle,open and close throttle. Throttle should besufficiently for engine to reach 1500 rpm. Amovement should he noticed in he EGR
away from EGR CTO switch.4 Disconnectvacuumhosesfrom CTO switch.5 Using7/8-inch open-endwrench,removeswitch
from intake manifold.
WARNING: Serious burns caii result if hot coolant isuof I rained btre removing switch ,from in takeill ill tld.
Installation-V-B Engine
1 Install EGR CTO switch in intakemanifold,2 Install coil andbracketwith attachingscrew.3 Connectvacuumhoseto switch.4 Install air cleanerassembly.5 Install coolantandpurgecoolingsystemof air.
EXHAUST BACK-PRESSURE SENSOR-NON-INTEGRALA non-integralexhaustback pressuresensoris used
on California JeepCJ modelswith V-8 engineand manual transmission.This device monitors exhaust back-pressureandpermits EGR operationonly when engineoperatingconditionsare favorablefor EGR actionwitha given engine/exhaustcombination.Back-pressuresensors are variously calibrated, are not serviceable,andmust he replacedwhen necessarywith the samepartnumber.
The exhausthack-pressuresensorconsistsof a diaphragmvalve and a spacerconnectedby a metal tubewhich pro.jects into an exhaustport in the spacerbodyfig. 4A-12. The EGR valve mounts directly on thespacer.
The metaltubeconnectingthe diaphragmvalveto thespacerpicks up exhausthack-pressurefrom the exhaustport into which it projects. When the back-pressurereachesthe calibratedlevel of the sensorthediaphragmvalve spring pressureis overcome,permittinga vacuumsignal to the EGR valve when the coolanttemperatureoverride CTO switch is open. Refer to EGR CTOSwitch in this section.
This systempermits EGR operationonly when theengine has warmed up sufficiently and when exhaustpressureis relatively high, as in acceleration and atsome cruising speeds. When hack-pressurehas notreachedcalibrated levels, or if the CTO switch has notopened,the carburetorvacuum signal vents to the atmospherefrom a vent at the diaphragmvalve.
Removal1 Remove vacuumlines from exhaustback-pres
suresensorvalve andEGR valve.2 Removetwo attachingnutsfrom EGRvalve.3 RemoveEGR valve and exhaustback-pressure
sensorassembly.4 Clean all mating surfacesand intake manifold
rectrouting.2 Install a teein vacuum line betweenEGR valve
andexhausthack-pressuresensor3 Attach a vacuumgaugeto tee.4 Start engine and allow to We. No vacuum
shouldhe indicated.
NOTE: if caco00 is imlico ted at ‘lie speed, i’ecifj cor-rect line connections. Be nie 1111 i//fOld cacen mis notbeing msed iS a son rce. It carbo,cfo c prociding ported
ii in, inspect for portia ll/j open f/i ii t tie plo fe, n’h ichcoold applj pee inatnie /oited ac’ ‘/0/ to hacl-pressure.5cii 501.
5 Accelerateengine to 2001 rpm and observevacuumgaugefor the following:
* If coolant temperatureis below 115°F, no vacuumshouldbe indicated.
*If coolant temperatureis above 115°F black CTOswitch or 160°F yellow CTO swftch, ported vacuum shouldhe indicated.
* If no vacuum was indicated durLng test, be surevacuum is being applied to inlet side of hack-pressuresensor.Then removehack-pressuresensorandinspect spacer port and tube for restrictions. Restrictions causedby carbon or lead depositscan beremovedwith spiral wire brush. Otherwise,replaceback-pressuresensor.
RESTRICTOR PLATES
NOTE: Restrictor plo te,s ore i,.cd oniij on iehicleseqoipped with the non-integral baci-prc.s.sure sensor.
The restrictorplatefig. 4A-13 is locatedbetweentheexhaust back-pressuresensor spacem and the intakemanifold, mountedbetweengaskets.The stainlesssteelrestrictor plate is calibrated for a particular engine/exhaustsystemand shouldnever be alteredor replacedwith a restrictorplate of different calibration.
EGR DELAY VALVEAn EGR delay valve is usedon 49-statemodelsequip
ped with 360 and 401 CID enginesarid 4V carburetor.The delay valve is installedbetweenthe EGR valve andCTO switch fig. 4A-14 and delaysthe vacuumsignaltothe EGR valve to prevent stumble or hesitationon initial acceleration.The delay valve is color codedto pre
vent improper installation. The red side of the valveconnectsto the CTO switch andthe blue side connectstothe EGR valve.
DELAY VALVE
Delay Valve Test
EGR VALVE
Fig. 4A-14 EGR Delay Valve
IDENTIFICATIONNUMBER LASTDIGIT OF PARTNUMBER
AJ43044
60710
1 Install a tee in vacuumline betweenred side ofdelay valve andvacuumsource.
operation, increaserpm until 3 to 10 inchesof vacuumare indicatedon the gauge. It should takefrom 18 to 32secondsfor the vacuumsignalto reachthe EGR valve.
4 Replacedelayvalve if delay is longer than 32 orless than 18 seconds.
5 While maintaininga 3- to 10-inch vacuum,disconnect CTO switch line from delay valve. EGR valveshouldcloseseatwithin 0.5 secondor less. If valvedoesnot seatwithin this time, replacedelayvalve.
GENERALAll V-8 CJ models,all altitude CJ models,a]] Califor
nia JeepmodelsCherokee,WagoneerandTruck modelshave a catalytic converter. Leadedfuel poisonsthe catalytic converter,althoughuseof a fewgallonsof leadedfuel in an emergencydoes not seriously impair theconverter.
All CJ modelsand all California Cherokee,Wagoneerand Truck models are fitted with a fuel filler neck restrictor refer to Fuel-Carburetionsection which admits only the smallernozzlesusedfor unleadedfuel.
Most models use a single pellet-filled canister-typeconverter.California V-8 modelsuse a monolithic-typeconverter.
coatedwith platinum and palladiumcatalyzingagents.Thousandsof pellets are containedin a stainlesssteelcanister.A plug is provided in the converterto permitreplacementof the pelletsshouldthey becomepoisoned.
The monolithic converter uses extrudedsubstratesresemblinga honeycomb.Eachsubstrateis coatedwitha mixture of palladium and platinum. The substratesare mountedend-to-endin a stainlesssteelcylinderandare retained by wire mesh and mounting rings. Thecatalystis not serviceable.
wherea chemicalchangetakesplace which reducescarbon monoxide and hydrocarbonsto harmlesscarbondioxide and water. The catalystswhich produce thisactionareplatinumandpalladium.
The temperatureof the converterduring this chemicalreaction is somewhathigherthan thatof exhaustgasesas they leave the engine. Due to its mass,the catalyticconverterstays hot much longer than the muffler.
The catalytic converterbody is stainlesssteel and isdesigne-dto last the life of the vehicle. Excessiveheatcan result in bulging or other distortion, but excessiveheat is not the fault of the converter.The vehiclehasacarburetor,ignition or Air-Guard problem permittingunburnedfuel to enterthe converter,producingexcessive heat. If a converteris heatdamaged,the causeof
PageGeneral 4A-16
damageshould be correctedat the sametime the converter is replaced,and all othercomponentsof the exhaustsystemshouldalso be checkedfor heatdamage.
CATALYST REPLACEMENT PROCEDURE-PELLET-TYPE1 Raisevehicle.2 Placevacuum pump hose on exhaustpipe and
tightenclampfig. 4A-15.
Fig. 4A-15 Vacuum Pump
3 Connectshopair 80 psi minimum to fitting onvacuumpump.
4 Removeplugfrom bottomof converter.
NOTE: It may be necessaryto apply heat directly tothe plug to easeremoval.
5 Positionvibrator on converterandlock in placefig. 4A-16.
6 Removeshopair hosefrom vacuumpump.7 Connect shop air hose to fitting on vibrator.
Catalyst beadswill fall into can for approximately10minutes.
CATALYTIC CONVERTER
vu
,
FITTING
‘VACUUMPUMP
A43045
AIR HOSEF ITTI N G
VIBRATOR
CAN
A43046
- EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-17
8 When converter is empty, disconnectshop air
hose,removecan, and discardbeads.9 Install refill beadcanon vibrator.
10 Connectshopair hoseto vacuumpumpand vi
brator. Beadswill be drawn up andpackedinto place.11 When converter is full, remove shop air hose
from vibrator andremovevibrator from converter.
NOTE: Replace ping if damaged during removal. Coatthreads qf Jiug with a nickel-based anti-seize compoundbtbre n.S to/lotion.
12 Install plug on bottom of converterand tightento 40 foot-poundstorque.
13 Disconnect shop air from vacuum pump andremovevacuumpump.
14 Lower vehicle.
FUEL TANK VAPOR EMISSION CONTROL SYSTEM
PageGeneral 4A-1 7Fuel Tank Filter 4A-11Fuel Tank Filler Cap 4A-1 7Fuel Vapor Storage Canister 4A-18
GENERALA closed fuel tank vent system is used on all CJ
modelsand California Cherokee,Wagoneer,andTruckmodels.This systemroutes raw fuel vapor into the intake systemwhere it is burnedalong with the fuel-airmixture, preventingfuel vapors from enteringthe atmospherefig. 4A-17. Other vehicles do not have ventlines sincethey do not use a closedvent system.
FUEL TANK FILTERAll vehiclesuse a woven Saransleevetypefuel filter
which is attachedto theendof thefuel outlet tube insidethe fuel tank. Thisfilter is ratedat 65 micron andrepels
water. Under normal conditionsit requiresno maintenanceor service.
FUEL TANK FILLER CAPThe filler capon California Cherokee,Wagoneer,and
Truck modelsandall CJ modelsincorporatesa two-wayrelief valve which is closedto atmosphereundernormaloperatingconditions. The relief valve is calibrated toopenonly when a pressureof 0.75 to 1.5 psi or a vacuumof 15 to 25 inchesof wateroccurswithin the tank.Whenthe pressureor vacuumis relieved,the valve returnstothe normally closed position. The capis identified by ablack relief valve housing.
vu
CLAMP
Fig. 4A-16 Vibrator Tool
4A-18 EMISSIONS CONTROLS - EXHAUST SYSTEMS
FUEL OUTLETLINE TOGAUGE FUEL PUMP
LOCKINGRING
FUELFILTER
FILLERVENTHOSE FILLER
HOSE
Fig. 4A-1 7 Fuel Tank Vapor Emission System Typical
NOTE: It is normal to occasionallyencounteran airpressure releasewhenremovingthefiller cap.
All other 49-statevehiclesuse an externally ventedcap.
LIQUID CHECK VALVEThe liquid check valve incorporatesa float and Viton
needleassembly.In the eventthat liquid fuel entersthecheck valve, the float will rise and force the needleupwardto closethe vent passage,preventingliquid fuelfrom flowing through the valve fig. 4A-18.
After passingthrough the checkvalve, the fuel vaporis routedthrough a vent line to the vaporstoragecanister in the enginecompartment.
ROLLOVER CHECK VALVECJ models havea rollover checkvalve locatedin the
vapor vent line fig. 4A-17 and4A-19. This valve servesto close the vaporline in the eventof a vehiclerollover,preventingthe possibility of a fuel-fed fire.
FUEL VAPOR STORAGE CANISTERThe fuel-resistantnylon body of the canistercontains
activated charcoalgranuleswhich absorbandstore the
fuel tank vapors until they are drawn into the intakemanifold throughthe carburetorair cleanerfig. 4A-20.
All canistershavethreenipple connections,althoughone connectionis plugged when used with the 2V V-8enginewhich doesnot requirea connectionto the carburetor float bowl.
In all otherapplications,the canisterhasconnectionsfor the fuel tank vapor line, the carburetorfloat bowlandto a tubeat the undersideof theair cleanersnorkel.
The tube at the snorkel projects into the incomingairstream, creating a vacuum that draws fuel vaporfrom the canister.The amount of vapor drawn is relative to air velocity passingthroughthe air cleanersnorkel. The canisteron six-cylinderenginesandV-S engineswith 4V carburetorshasthreehoseconnections:one forthe fuel tank vapor line, one for the carburetor floatbowl, andone hoseconnectedto a tube at the undersideof the air cleanersnorkel.
Outsideair is drawn into the canister through a replaceablefilter padwhich is accessiblethroughthe bottom of the canister body. The filter pad should bereplacedat the recommendedmileageintervals listed inthe MechanicalMaintenanceSchedule.
MAINTENANCEThe fuel tank, filler cap, fuel lines, and vent lines
must be maintainedin good condition to prevent rawfuel vapors hydrocarbons from entering theatmosphere.
Inspect the filler cap for evidence of fuel leakagestains at the filler neck opening.Removethe capandcheck the condition of the sealing gasket. Replacethefiller capif thegasketis damagedor deteriorated.
Inspect the fuel tank for evidence of fuel leakagestains. Traceany stainback to its origin and repairorreplacethe tank as required.
If liquid fuel is present at the fuel vapor storagecanister, inspect the liquid check valve and replaceifnecessary.
The filter pad locatedat the bottomof the canisteris60277 the only serviceableitem of the canisterassembly.For
service intervals, refer to the MechanicalMaintenanceSchedulelocatedin Section B of this manual.
1
FLOAT
NE EIDLEASSEMBLY
VAPOR INLETSFROM FUEL TANK A42016
COVER
AJ41 254
VAPOROUTLET
VAPORIN LET
STAINLESSSTEEL BALL
HOUSING
Fig. 4A-19 Rollover Check Valve
4A-20 EMISSIONS CONTROLS - EXHAUST SYSTEMS ru
POSITIVE CRANKCASE VENTILATION PCV SYSTEM
Page PageGeneral 4A-20 PCV Valve Flow Chart 4A-21PCV Air Inlet Filter 4A-21 PCV Valve Test 4A-21
GENERALThis system incorporatesa calibrated airflow PCV
valve connectedbetween an intake manifold vacuumsource and the engine. Crankcasevapors are drawnthrough the PCV valve into the intake manifold wherethey areburnedalong with the fuel-air mixturefig. 4A-21. The oil filler cap is closedin this systemto preventany crankcasevaporsfrom enteringthe atmosphere.
During periods of relatively high manifold vacuum,such as idle or cruisespeeds,outsideair is drawn fromthe air cleanerinto the crankcase.On six-cylinder engines, the air passesthrough a polyurethanefoam filterlocated in the air cleanerfig. 4A-22. On V-8 engines,the air passesthrough a polyurethanefoam filter locatedin theoil filler cap.Thefiller capis connectedby ahose to the air cleanerfig. 4A-23.
If crankcasevaporpressuresblowby exceedthe flowcapacity of the PCV valve, airflow in the systemwillreverse. Crankcasevapors are drawn through the aircleanerelementandcarburetorand burnedalong withthefuel-air mixture.
The positive crankcaseventilation systemperformstwo functions:
* Prevents combustion blowby from entering theatmosphere.
* Ventilatesthe crankcasewith cleanair to help prevent the formation of sludge.
Positive Crankcase Ventilation PCVJ ValveTwo PCV valves with different flow ratescfm are
used.The black valve is usedon all V-8 enginesandthesilver valve is usedon all six-cylinderengines.
AJ4201 7
Fig. 4A-22 PCV System-Six-Cylinder
MANIFOLD
-4-
AJ4 1256
HOSE TOMANIFOLDVACUUMSOURCEATCARBURETOR
NON-VENTEDOIL FILLERCAP
PCvVALVEINSTALLEDIN INTAKEMANIFOLD
Fig. 4A-23 PCV System-V-8
EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-21
The PCV valvemustbereplacedat the intervalsspecified in the MechanicalMaintenanceSchedule.All hosesin the PCV systemshould be inspectedat this time forleaksor restrictionsandcleanedor replacedas required.PCV valve replacementmay be required more oftenunderadverseoperatingconditions.
PCV VALVE TESTThevalve may be testedat idle speedfor correct flow
ratecfm providing the enginemanifold vacuum is atleast 14 inchesHg. When checkingvacuum,connectthegaugeto a fitting which is as centrally locatedas possible on the intake manifold.
Remove the valve from the grommet in the intakemanifold V-8 or cylinderheadcover six-cylinder andconnectthe plastic hoseof PCV Valve TesterJ-23111tothe valve fig. 4A-24.
NOTE: The PCV Valve must bE held in a horizontalposition and tapped ightiy duriog the test. Hold thetester in a verticalposton.
Start the engineand allow it to idle and observetheflow ratecfm. Refer to PCV Valve Flow Chart.At lowvacuumreadings,it may be necessaryto load the enginewhile checkingflow rate.
A valve which flows aboveor below specificationmustbe replaced.The correctPCV valve should be usedforreplacement.
PCV Valve Flow
ENGINEMANIFOLD
VACUUMIn. Hg.
AIR FLOW CFM
BLACK VALVE SILVER VALVE
171613753
-
1.35-1.65-
2.7-3.8-
3.3-4.4
1.3-1.7-
1.3-1.7-
1.3-1.7-
PCV AIR INLET FILTER MAINTENANCE
Six-Cylinder
70495
A polyurethanefoam PCV air inlet filter is locatedina filter retainer in the air cleaner.The retainermust berotated to remove it from the air cleanerfig. 4A-25.The filter must be cleanedin keroseneat the mileageintervalsrecommendedin the MechanicalMaintenanceSchedule.After cleaning, the filter should be lightlyoiled with clean engineoil.
V-8A polyurethanefoam PCV air inlet filter is locatedin
the sealedoil filler cap.To cleanthe filter, apply light airpressurein reversedirection of normal flow; that is,through thefiller tubeopeningof thecap.Lightly oil thefilter with clean engineoil. If the filter is deteriorated,the filler capmust be replaced.
THERMOSTATICALLY CONTROLLED AIR CLEANER LTAC SYSTEM
SIX-CYLINDER ENGINEThis systemconsistsof a two-pieceheat shroudposi
tioned on the exhaustmanifold, a hot air hose,and an
air duct and valve assemblywhich is locatedin the aircleanersnorkel fig. 4A-26.
The air duct and valve assemblyincorporatesan airvalve, a thermostatunit, anda spring.
1
MOULDEDHOSE
Fig. 4A-24 PCV Valve Test Fig. 4A-25 PCV Air Inlet FIlter-Six-Cylinder
AJ43048
4A-22 EMISSIONS CONTROLS - EXHAUST SYSTEMS
The temperatureof the air enteringthe air cleaneristhermostatically controlled by the air duct and valveassembly.Air from the enginecompartment,or heatedair from the shroudedexhaustmanifold is supplied tothe engine.
The thermostat unit in the air duct is exposedtoincomingair. Thespring-loadedair valve is connectedtothe thermostatunit through linkage. The spring holdsthe air valve in the closed position heat on until thethermostatunit overcomesthe spring tension.
During the enginewarmup period when the air temperatureenteringthe air duct is less than 105°F90°Fon 258 2V, the thermostat is in the retractedpositionand the air valve is held in the closedpositionheatonby the spring,thus shuttingoff the air from the enginecompartment.Air is thendrawnfrom the shroudat theexhaustmanifold.
As the temperatureof the air passingthe thermostatunit rises,thethermostatstartsto openandpulls theairvalve down. This allows cooler air from the enginecompartment to enter the air cleaner. When the temperatureof the air reaches130°F, the air valve is in theopenpositionheatoff so thatonly enginecompartmentair is allowedto enterthe air cleaner.
Fig. 4A-26 TAC System-Six-Cylinder
TAC Operational Test-Six-Cylinder1 Removeair cleanertop half andhold snorkel in
cold water, making certainthermostatunit is covered.2 Placea thermometerin water and observe the
temperaturewhile slowly turning on hotwater.
NOTE: With water temperatureat 105 °F 90°F on 2582l7 or less,air valvemustbein closedheat onposition.
3 Heatwateruntil temperaturereaches130°F; airvalvemust be in fully openheatoff position.
NOTE: If air valve doesnot openand closeat temperatures specified, checkvalve mechanismfor a bindingcondition or a disconnectedor defectivespring. If valvemechanismis insatisfactorycondition, thermostatunitis defective and air cleanerassemblymustbereplaced.
V-8 ENGINEThis system consistsof a heat shroud which is in
tegral with the right-handexhaustmanifold, a hot airhose,a special air cleanerassemblyequippedwith athermal sensor, and a vacuum motor and air valveassembly.
The thermal sensorincorporatesan air bleedvalvewhich regulatesthe amount of vacuum applied to thevacuummotor, therebycontrollingthe air valve positionto supplyeitherheatedair from theexhaustmanifold orair from the enginecompartmentfig. 4A-27.
AIR BLEED THERMALVALVE OPEN SENSOR
AIR It MANIFOLDVACUUM
I I
_
1/ 11 1SNORKEL AIR VALVE CLOSED
HEAT OFF POSITION
AIR BLEEDVALVE CLOSED
THERMALSENSOR
SPRING VACUUM
DIAPHRAGM
MOTOR
SNORKELMANIFOLD
AIR VALVE OPEN HEATEDHEAT ON POSITION AIR 70424
ri
AIR VALVE OPENHEAT OFF POSITION
ENGINECOMPARTMENTAIR
AIR VALVE CLOSEDHEAT ON POSITION
THERMOSTATUNIT RETRACTED HEATED AIR
60349
Fig. 4A-27 TAC System-V-8
EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-23
During the warmupperiod when underhoodair temperaturesare low, the air bleed valve is closed andsufficient vacuum is applied to the vacuum motor tohold the air valve in the closedheat on position.
As the temperatureof the air enteringthe air cleanerapproachesapproximately 115°F, the air bleed valveopensto decreasethe amountof vacuum appliedto thevacuum motor. The diaphragmspring in the vacuummotor then moves the air valve into the open heatoffposition, allowing only underhoodair to e:nter the aircleaner.
The air valve in the air cleanersnorkel will also open,regardlessof air temperature,during rapid accelerationto obtain maximumairflow throughthe air cleaner.
TAC Operational Test-V-81 Removeair cleanerassemblyfrom engine and
allow to cool at room temperature2 After cooling, sight through air cleanersnorkel
to observepositionof air valve. It shouldbefully opentooutsideair.
3 Install air cleanerassemblyto engineand connecthot air tube andmanifold vacuumhose.
4 Startengineandobserveposition of air valve, itshould be fully closedto outsideair.
5 Move the throttle leverrapidly to approximately1/2 to 3/4 openingand release.Air valve should openand thencloseagain.
6 Allow engineto warm to operatingtemperatureand observeposition of air valve. It should befully opento outsideair.
If air valve does not close at room temperaturewithvacuum applied, check for a mechanicalbind in thesnorkel,disconnectedvacuummotor linkage,or vacuumleaks in hosesor connectionsat the vacuummotor, thermal sensorandintakemanifold.
If air valve mechanismis operating freely and novacuum leaks are detected,connecta hose from an intakemanifoldvacuumsourcedirectly to vacuummotor.
If air valve now closes,thermalsensoris defectiveandmustbe replaced.
If air valve doesnot close, vacuummotor is defectiveand must be replaced.
VACUUM THROTTLE MODULATING SYSTEM VTM
This system is designed to reduce the emission ofhydrocarbonsHC during rapid throttle closureat highspeeds.It is not usedon CJ models,but is usedon some49-State and all California Cherokee,Wagoneer, andTruck modelswith V-8 engine.
The systemconsistsof a decelerationvalve locatedatthe right front side of the intakemanifold anda throttlemodulatingdiaphragmlocated at the carburetorbase.The decelerationvalve is connectedby one hose to amanifold vacuum source and by another hose to thethrottle modulatingdiaphragmfig. 4A-28.
During high speeddeceleration,when manifold vacuumreachesapproximately21 to 22 inches, the deceleration valve triggers a vacuum signal to the throttlemodulatingdiaphragmandcausesaplungerto move outand open the throttle slightly. The increasedthrottleopeningallows more air to enterthe combustionchambersandleanout theoverrichmixture, therebyreducingthe emissionof the hydrocarbons.
The decelerationvalvecalibration is presetat time ofmanufactureandnormally doesnotrequireadjustment.To checkandadjustthethrottle modulatingdiaphragm,proceedas follows:
1 With engine not running and curb idle speedpreviously set, position throttle lever againstcurb idleadjustingscrew.
2 Measureclearancebetweenthe throttle modulating diaphragm plunger and the throttle lever. Itshouldbe 1/16 inch 0.062inch.
3 Adjust by looseningthejamnutand turning thediaphragmassembly.
GeneralSolenoid Control SwitchSolenoId Vacuum Vaive
PageSpark Coolant Temperature Override Switch 4A-26TCS Test 4A-25
GENERALThepurposeof this systemis to reducetheemissionof
oxidesof nitrogenby loweringthe peakcombustiontemperature during the power stroke. The system incorporatesa solenoidvacuum valve, a solenoidcontrolswitch, andrelatedwiring andvacuumlines fig. 4A-29and 4A-30. This systemis used on California CJ V-8models, California CJ six-cylinder models with automatic transmissionand altitude CJ modelswith automatic transmission.
SOLENOIDVACUUMVALVE
SOLENOID CONTROLSWITCH . OPEN INHIGH GEAR MANUALTRANSMISSION
AJ41 260
INTAKE MANIFOLDVACUUM SOURCE OUTER PORT 1-
CENTER PORT D-
INNER PORT 2-
Fig. 4A-30 TCS System-V-8
OPEN BELOW160°FALWAYSOPENOPEN ABOVE160°F
J43191
FIg. 4A-29 TCS System-Six-Cylinder
SOLENOID VACUUM VALVEThis valve is attachedto the intake manifold at the
rearright side of the intakemanifold V-8 enginesor to
a bracketat the rearof the intakemanifold six-cylinderengines.When the valve is energizedground circuitcomplete,carburetorported vacuumis blockedandthedistributor vacuum line is vented to atmospherethrough a port in the valve, resulting in no vacuum
"I
Page4A-244A-254A-24
INTAKEMANI FOLDVACUUMSOURCE
IGNITIONFEED
PORT 1TO MANIFOLDVACUUM
‘1 EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-25
advance.Whenthe valve is de-energizedground circuitopen, ported vacuum is applied to the distributor resulting in normalvacuumadvance
SOLENOID CONTROL SWITCHThis switch opensor closesaccordingto gear selection
manual transmissionor road speedautomatic transmission. In manual transmissions.the solenoidcontrolswitch is closed in neutraland in all gears excepthighgear. Vacuumadvanceis possibleonly when the transmission is in high gear.The switch on automatictransmission-equippedvehiclesopensat a pre-setroadspeedwhen the vehicle is acceleratingand closes at a lowerroad speedwhen the vehicle is decelerating.Refer toAutomatic TransmissionSolenoid Switch Calibrationschart.
California6 cyl and 8 cyl 34 to 38 mph 22 to 28 mph
Altitude6 cyl
28 to 32 mph 20 to 26 mph
Altitude8 cyl 34 to 38 mph 22 to 28 mph
70548
On manual transmissions,the switch is operatedbythe shifter shaft,which is screwedinto thetransmissioncase.
On automatic transmissions,the switch is locatedalong the speedometercable on the dash panel. Theswitch is operatedby speedometercablerpm. The cableattachesto both endsof the switch.
TCS TESTA vacuumgauge,probe-typetest lamp and a jumper
wire are usedto check the operationof the TCSsystem.The testsdetermineif thesolenoidhasa currentsupply,if the solenoidcontrol switch opensand closesthe solenoid groundcircuit properly, and if the vacuumvalve isfunctioning. Refer to fig. 4A-31
Test 1-Current Supply Test1 Turn ignition switchON.2 Disconnect wire connector from solenoid vac
uumvalve.3 Connectwire leadof test lampto ground.4 Touchprobeend of testlamp to each terminal of
connector.Test lamp should light at terminal of orangewire. If not, ignition feed to TCS systemis diefective.
Test 2-Ground Circuit Test-Manual Transmission1 Move gearshiftleverto NEUTRAL.2 Connecttestlamp wire to batterypositivepost.
Touchprobeto tan wire terminal in solenoidconnector.Test lamp should light.
3 Shift transmissionto each gear exceptHIGH.Test lamp should remainlit.
4 Shift transmission to HIGH gear. Test lampshouldgo out.
If testlamp doesnot light at all, performTest4-So-lenoid Control Switch Test.
Test 3-Ground Circuit Test-Automatic Transmission1 Support vehicle so all four wheels are off
ground.2 Connecttestlamp wire to batterypositivepost.3 Disconnectwire connector from solenoidvac
uum valve andinsert probein tan wire terminal.4 Start engine and put transmissionin DRIVE.
Observetest lamp. Note speedat which testlamp goesout switch opens.Slowly decelerateand notespeedatwhich test lamp goeson switch closes.
6 Replacevalve if defective. Be sure to connectvacuumlinescorrectly.
4A-26 EMISSIONS CONTROLS - EXHAUST SYSTEMS
TOSOLENOIDCONTROLSWITCH
IGNITION FEED
ri
TEST 1 - CURRENT SUPPLY TEST
It
TAN TOSOLENOIDCONTROLSWITCH
IGNITION FEED
TEST 2 AND TEST 3 - GROUND CIRCUIT TEST
TEST 4- SOLENOID CONTROL SWITCH TEST AUTOMATIC TRANSMISSION SHOWN
Fig. 4A-31 TCS System Test
60465
SPARK COOLANT TEMPERATURE OVERRIDE SWITCHSPARK CTO
This switch is threadedinto the thermostathousingon V-8 enginesandinto the left rearside of the block onsix-cylinder engines. Its purpose is to improve driveability during the warmup period by providing fulldistributor vacuum advanceuntil the engine coolanttemperaturehas reached 160°F. The switch incorporatesa thermalunit which reactsto coolant temperaturesandmovesacheckball inside the switchup ordown to open or close the switch ports. Either intakemanifold or carburetorported vacuumis routedto thedistributorvacuumadvancediaphragmfig. 4A-32.
When the coolant temperatureis below 160°F, portsNo. 1 andD areopenandport No. 2 is closed.When thecoolant temperaturereaches160°F, port No. 1 closesandports No. 2 andD areopen.
RETURNSPRINGS3
THERMALSENSOR
TAN
TAN
DISCONNECTED
ORANGE
JUMPERWIRE
II
SOLENOIDCONTROLSWITCH
PORT NO. 1
-PORT D
PORT NO. 2
BALL
AJ42024
Fig. 4A-32 Spark CTO
P EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-27
Spark CTO Test
NOTE: Begin test with coolant temperature below160 °F.
1 Removeall vacuumlines from CTO switch.Plugthose lines that will createa vacuumleak.
2 Connecta vacuumline from a manifoldvacuumsourceto port No. 1 outer of the CTO.
3 Connecta vacuumgaugeto port D center ofCTO.
4 Start engine. Manifold vacuum should be indicatedon vacuumgauge.If not, replaceCTO.
5 With engine still running and coolant temperature below 160°F, disconnectvacuumline from portNo. 1 outer of CTO andconnectto port No. 2 inner.
6 No manifold vacuumshouldbe indicatedon vacuum gauge.ReplaceCTO if vacuumis indicated
7 Keep enginerunning until coolanttemperatureexceeds160°Fapproximatelythe beginningof the temperaturegaugeband. Manifold vacuum should be indicated.If not, replaceCTO.
8 Disconnectline from port No. 2 andcon:nectit toport No. 1. No vacuumshouldbeindicated. If vacuumisindicated,replaceCTO.
9 Reconnectvacuumlines to CTO.
Spark CTO Replacement
Removal-Six-Cylinder1 Draincoolantfrom radiator.2 Disconnect vacuum lines from
switch.spark CTO
3 Placea drain pan under the enginebelow CTOswitch.
4 Using a 7/8-inch open end wrench, removeswitch from block.
WARNING: Be careful of scaldinghot water leakingfrom blockwhenremovingthe switch.
NOTE: Removetemperaturegaugesendingunit fromhead to aid in bleeding air while filling the coolingsystem.
Removal-V-8 Engine
1 Draincoolantfrom radiator.2 Remove air cleanerassembly,coil and bracket
assembly.3 Disconnectvacuumlines from CTO switch.4 Using a 7/8-inch open end wrench, remove
switch from thermostathousing.
Installation-V-B Engine
1 Install sparkCTO switch in thermostathousing.2 Installcoil andbracketwith attachingscrew.3 Connectvacuumlinesto switch.4 Install air cleanerassembly.5 Install coolant.6 Purgecooling systemof air.
GENERAL
EMISSION CONTROL MAINTENANCE
Proper emission control dependson overall engineperformanceaswell as specialemissioncontrol systems.The following procedurescover maintenanceserviceslisted in the U. S. Emission Control ServicesChartwhich havenot beendescribedearlier in this section.
PageCarburetion 4A-33Diagnosis with Scope Analyzer 4A-33General 4A-27
PageIgnition System 4A-27Tuneup Specifications 4A-38U.S. Emission Control Services 4A-28
IGNITION SYSTEM
Spark PlugsSpark plugs should be removedand examinedfor
recommendedin the U. S. Emission Control ServicesChart. Plugs with lower mileagemay be cleanedundersomecircumstancesrefer to fig. 4A-33. After cleaning,the centerelectrodeshouldbefiled flat with a point file.The gapmustbe set to 0.033to 0.037 inch fig. 4A-34.
U.S. Emission Control Service-Cherokee-Wagoneer-Truck Models
Spark Plug Condition
70497A
Refer to figure 4A-33.GapBridging-A--May betracedto flying deposits
in thecombustionchamber.In a few cases,fluffy deposits may accumulateon theplugsduring in-town driving;when the engineis suddenlyput underheavyload, thismaterial canmeltand bridgethe gap.
ScavengerDeposits-B-Fuel scavengerdepositsshownmay be white or yellow. They may appearto beharmful but this is normal appearancewith certainbrand fuels. Suchmaterialsaredesignedto changethechemicalnatureof depositsto lessenmisfire tendencies.Notice that accumulationon the ground electrodeandshell areasmaybe unusuallyheavy,but the material iseasilyremoved.Suchplugscan be considerednormal incondition, andcanbecleanedusingstandardpractices.
U.S. Emission Control Service-CJ Models
1
70497B
ChippedInsulator-C-Usually results from bending the centerelectrodeduring regappingof the plug.Under certain conditions, severedetonation can alsosplit insulator firing ends.
Pre-ignition Damage-.--D--.-Causedby excessivetemperatures,producesmelting of the centerelectrodeand, somewhatlater, the ground electrode.Insulatorswill appearrelatively clean of deposits.Check for correct plug heatrange,overadvancedignition timing andsimilar reasonsfor overheating.
Cold Fouling or Carbon Fouled-E-Dry, blackappearanceof oneor two plugsin a set. Checkfor sticking valvesor badignition leads.Fouling of the entiresetmay be causedby a clogged air cleaner,a sticking exhaustmanifoldheatvalve, or afaulty choke.
Overheating-F-Indicatedby adeadwhite or grayinsulatorwhich appearsblistered.Electrodegap wearratewill be considerablyin excessof 0.001 inch per 1000miles.This maysuggestthat a coolerheatrangeshouldbe used; however,overadvancedignition timing, detonation, and cooling system stoppagescan also causeoverheating.
A precision electronic diagnosis should be purchased wheneverquestionable engine performance occurs between the scheduledcomplete precision tune-ups.
COMPLETE PRECISION TUNE-UPAt 30-60-90,000 milesAir-Guard System Hoses-inspect and correct if requiredCarburetor Air Cleaner Element-replaceChoke Linkage-inspect for free movement correct if requiredCoil and Spark Plug Wires-inspect and replace if requiredDistributor Advance Mechanisms-check and correct if requiredDistributor Cap and Rotor-inspect and replace if requiredDrive Belts-inspect condition and tension and correct if required*EGR System-inspect hoses and connectionsEngine Oil Filler Cap filter type-clean and soak in engine oilFuel Filter Element-replaceFuel System: Cap, Tank, Lines and Connections-inspect for
integrity and correct if requiredFuel Vapor Inlet Filter at Charcoal Canister-replaceHeat Valve exhaust manifold-inspect and lubricateIdle Speed curb and fast and mixture-check and reset if
requiredIgnition Timing-check and set if requiredPCV Filter 6-cylinder-cleanPCV Hoses-inspect and replace if requiredPCV Valve-replaceSpark Plugs-replaceTAC System Hoses-inspect and correct if requiredTransmission Controlled Spark Systems-inspect and correct if
requiredVacuum Fittings, Hoses and Connections-inspect and correct
if required
A precision electronic diagnosis should be purchased wheneverquestionable engine performance occurs between the scheduledcomplete precision tune-up.
COMPLETE PRECISION TUNE-UP
At 15-30-45-60-75-90,000 milesEngine Oil Filler Cap filter type-clean and soak in engine oilExhaust Gas Recirculation Valve-inspect and clean*Exhaust Gas Recirculation Discharge Port six-cylinder-
inspect and clean if requiredDrive Belts-inspect condition and tension and correct if requiredCarburetor Air Cleaner Element-replace paper cartridge, clean
polyurethane element, unless plugged ordamaged, then replaceFuel Filter Element-replaceHeat Valve exhaust manifold - inspect and lubricatePCV Valve-replacePCV Filter six-cylinder-c leanPCV Hoses-inspect and replace if requiredCoil and Spark Plug Wires-inspect and replace if requiredSpark Plugs- replaceIgnition Timing-check and set if requiredDistributor Advance Mechanisms-check and correct if requiredDistributor Cap and Rotor-inspect and replace if requiredIdle Speed and Mixture-check and reset if requiredChoke Linkage-inspect for free movement correct if requiredFuel System: Cap, Tank, Lines and Connections-inspect for
integrity and correct if requiredFuel Vapor Inlet Filter at Charcoal Canister-replaceAir-Guard System Hoses-inspect and correct if requiredTAC System-inspect and correct if requiredVacuum Fittings, Hoses and Connections-inspect and
correct if required . .* Not applicable to California models
* LOW MILEAGE PLUGS WITH THIS CONDITION MAV BE CLEANED
-EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-29
** PLUGS WITH THIS CONDITION MUST BE REPLACED
Fig. 4A-33 Spark Plug Conditions
bootanl lift straightup with a steady,evenpull. Do notpull on the wire itself as this will damagethe wire.
To remove wires from the distributor cap or coiltower, loosenthe boot first, thengraspthe upperpartofthe bootandthe wire andgently pull straight up.
Wire TestDo not puncturethe spark plug wires with a probe
while performingany test.This may causea separationin the conductor.Thepreferredmethod is to removethesuspectedwires andusean ohmmeterto testfor resistanceaccordingto the length of the particularwire.
Resistance ValuesWhen installing each sparkplug wire or the coil high
tensionwire, be certaina good,tight connectionis madeat the spark plug, distributor cap tower, or coil tower.The protector boots at the spark plugs and distributor
42025 cap must fit tightly. A partially seatedwire createsanadditional gap in the circuit and the resulting sparkjump will causeterminal corrosionandwire damage.
Spark Plug WiresTo remove wires from spark plugs, twist the boot
slightly to break the seal. Graspthe rubber protector
lgnftion CoilWhenan ignition coil is suspectedof being defective,
it should be checkedon the vehicle. A coil may breakdown after it has reachedoperatingtemperature.It is
1-
A*
C**
E F**
60770
Fig. 4A-34 Spark Plug Gap Check
4A-30 EMISSIONS CONTROLS - EXHAUST SYSTEMS
important that the coil be at operatingtemperaturewhen tests are made. Perform the testsfollowing theinstructionsof the testequipmentmanufacturer.Referto Ignition Systemin Section3-Electrical.
Resistance Values
Inches Ohms
Oto 15
15 to 25
25 to 35
Over 35
3,000 to 10,000
4,000 to 15,0006,000 to 20,000
8,000 to 25,000
Distributor
60748
The distributorusedon all enginesis the breakerlesselectronic type. There is no scheduledmaintenanceforthis distributor. Refer to Section 3-Electrical for distributor serviceprocedures.
Distributor Rotor
NOTE: Six-cylinder vehicles sold in Canada have a5000-ohmresistancebuilt into the rotor for additionalradio noise suppression.
The rotor shouldbe inspectedvisually for cracks,evidence of burning on the top of the metal strip, or evidenceof mechanicalinterferencewith the capfig. 4A-35. If any of the aboveconditionsare found, the rotorshould be replaced.Someburning is normal on the endof the metal strip. This shouldnever be filed.
Initial Ignition Timing
1
Distributor CapThe distributor cap should be removed and wiped
clean with a dry rag. A visual inspectionshouldbemadefor cracks, carbon runners,and corrodedhigh tensionterminals fig. 4A-36. If any of theseconditions arefound, the capshould be replaced.In replacingthe cap,be sure that the high tensionwires are installed in thesametowers from which they were removedand thatthey arepusheddown firmly in place.
If the insertsinsidethe capareexcesivelyburned,thecapshould be replaced.Howeverthe vertical face of theinsert will show some evidenceof burning through normal operation. The inserts should also be checkedforevidenceof mechanicalinterferencewith the rotor tip.
A graduateddegreescale locatedon the timing casecover is used for timing the ignition system. A millednotch on the vibration damperis usedto referencetheNo. 1 firing position of the crankshaftwith the timingmarkson the scaleas shown in figures4A-37 and4A-38.
NOTE: IJ’a timing light incorporatingan advancecontrol feature is used, the control must be in the offposition.
3 Startengine.4 Adjust idle speed to 500 rpm with solenoid
disconnected.5 Adjust initial ignition timing to settingspecified
on the TuneupSpecificationsOn Vehicle Chart by loosening the distributor holddown clampand rotating thedistributor.
6 Verify ignition timing after tighteningdistributor hoiddownclamp.
Distributor Advance-On TesterDistributor advancemay be testedwith the distribu
tor out of the vehicle. Follow testingequipmentmanufacturer’sinstructions.
Information given in the Distributor Curveson vehicle chartsis for on-vehicle testing. If the distributoradvanceis checkedon a distributor tester,the information in the Distributor Curvesmust be convertedfromengineRPM to distributor RPM and from engine de
ROTORgrees to distributor degrees.Engine RPM must be di-
TIP vided by 2 to obtain distributor RPM. Engine degreesCORRODED advancemust be divided by 2 to obtain distributor de
grees advance.For instance,if the Distributor Curve70202 indicates 8 to 12 degressadvanceat 2000 RPM, the
correspondingon-testerspecificationswould be 4 to 6degreesadvanceat 1000 RPM.
INSUFFICIENTSPRINGTENSION
EVIDENCEOFPHYSICALCONTACTWITHCAP
Fig. 4A-35 Rotor Inspection
ru -- EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-31
BROKENTOWER
Fig. 4A-36 Distributor Cap Inspection
Adjustable Advance Control Timing Light Procedure1 Disconnect the TCS solenoid vacuum valve
BURNED ORERODED TERMINALS
CARBON PATH
WORNCARBON PATH OR
DAMAGEDROTORBUTTON
70203
Fig. 4A-37 Timing Mark location-Six-Cylinder
Fig. 4A-38 Timing Mark Location-V-8
2 Increaseenginespeedto 2000 rpm.3 Turn advancecontrol of ignition timing light
until the ignition timing has returned to the initialsetting.
NOTE: The degree reading on the advance metershould be as specifiedin the TuneupSpecificationOnVehicle,Chart.wires.
4A-32 EMISSIONS CONTROLS - EXHAUST SYSTEMS ri
POINT SYSTEM
FIRING LINE SPARK LINE COIL RESERVE POINT CLOSE POINT OPEN
5 KVAT NEARLY I1000 RPM LEVEL I UNUSED ENERGY - SHORT DOWNWARD ABRUPT 90°
NO MORE OSCILLATIONS, I SPIKE FOLLOWED ANGLE -I GRADUALLYDIMINISH i BYGRADUALLYSMALLER STARTOFIN SIZE OSCILLATIONS NEXT CYLINDERVARIATION
FIRING LINECYLINDERS
nTESTS: I TESTS: I TESTS: TESTS: TESTS:PLUG AND I PLUGS.WIRES I DEFECT IN COIL, DIRTY,BURNED PITTED POINTSROTOR GAP, CAP. ROTOR. CONDENSER, OR OR MISALIGNED OR ARCING FROMBROKEN WIRES OR ENGINE PRIMARY CIRCUIT. POINTS AND POOR CONDENSERFUEL MIXTURE. CONDITION WEAK POINT TENSION. ACTION.
AFFECTINGPLUG FIRING.
I PULL OFF PLUG WIRE - FIRING LINE SHOULD RISEI TO 20 KV OR MORE FOR NORMAL COIL OUTPUT. PAT
1 TERN SHOULD ALSO EXTEND BELOW ZERO LINE INDICATING GOOD INSULATION.
BID SYSTEM
TESTS: A B C DPLUGAND I ‘ IROTOR GAP, IBROKEN WIRES, IFUEL MIXTURE. I I
CURRENTI I REGULATION
I I
__-_____ _____
I PLUGS. WIRES I ICAP. ROTOR. COIL TRANSISTOR - ON
I OR ENGINE I INTERMEDIATE I COIL SECTIONCONDITION I SECTIONAFFECTING
I PLUG FIRING. I60471
Fig. 4A-39 Diagnosis Pattern Chart
EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-33
4 If the total advance at 20O rpm is less thanspecified, disconnect vacuum advance hose atdistributor.
If the centrifugaladvancedegreesareas specified,thevacuumunit musthe replaced.
DIAGNOSIS WITH SCOPE ANALYZERThe scopeanalyzeris an ignition testerthat provides
quick and accurate diagnosis of ignition system performance. All phasesof the ignition cycle are showngraphicallyon an oscilloscopecathoderay tubeas theyoccur in engineoperation.
The manufacturersof scopeanalyzerequipmentprovide adequatedescriptionsof test procedurespossiblewith their equipment.This sectiun is not intended tocover all usesof Scopeequipment,hut to pointout differencesin scopepatternbetweenthe conventional"point"systemand the BID BreakerlessInduction Dischargesystemusedon Jeepvehicles.
Refer to figure 4A-39. The uppersection of the chartshowsa typical scopepatternof the point systemfromfiring line to firing line andareasof the patternsignificantto diagnosis.
The scope pattern waveform shows time durationhorizontally and voltage vertically. Bearing this inmind, note the lower section of the chart which showsthe typical patternof the BID sytern.
Note the somewhatlonger duration of the spark lineshown on the BID pattern-this longerspark providessuperior combustionwith the leaner air-fuel mixturesnow used.
The BID waveform pattern is below zero line in thecoil sectionbut otherwiseis similar to that of the pointsystemin this area.
In the final "dwell" section of the scopepattern, a"worm" appearsjust above the zero line on the BIDpattern.This wiggle is causedby the automaticcurrentregulator built into the ECU Electronic Control Unitcircuitry andis entirely normal. Sincethis sectionof thepatternis underelectroniccontrol, it will not vary fromcylinder to cylinder as in the point system where thisdwell areais controlled mechanically.
Other than the difference described,scope ignitiondiagnosisproceduresfor point and BID systemsis essentiallythe same.
CARBURETION
Engine Idle Speed and Mixture Setting ProceduresThe engineand related systemsmust be performing
properlyprior to making carburetoridle speedand mixture adjustments.The idle speedand mixture adjustments must be made with the engine at operatingtemperatureand air cleanerin placefig. 4A-40, 4A-41,4A-42 and4A-43.
Fig. 4A-40 Model YF Carburetor
ru
AJ43052
IDLE MIXTUREADJUSTING SCREWS
Fig. 4A-41 Model BBD Carburetor
60466
/SPARK LIMITER EGRPORT CAPS PORT AJ42039
Fig. 4A-42 Model 2100 Carburetor
4A-34 EMISSIONS CONTROLS - EXHAUST SYSTEMS
Plastic idle limiter caps are installed over the idlemixture screws on all carburetors.The limiters aredesignedto regulate the adjustmentrange of the idlemixture screws,therebyeffectively controllingthe exhaustemissionlevel at idle speedsto comply with Federal Standardsfor emissioncontrol. The limiter capsmust be removedin order to perform the leandrop idlesetting using the tachometerprocedure.The infraredanalyzerproceduresdo not normally require limiter capremoval.
Proper idle speedand mixture adjustmentscan bemadeby following a standardtachometerprocedureinwhich the idle mixture is adjustedto a lean drop idlesetting.A infraredIR analyzerprocedure,in which theidle mixture is adjustedto obtain a specified carbonmonoxidelevel, may be used,but only on vehicleswithout a catalyticconverter.When following the tachometer procedure,adjustmentsmust be madein the exactdetailedsequenceoutlined to obtain lean drop idle settings andsatisfactoryidle quality.
WARNING: Setpark brakefirmly. Do not accelerate.
Tachometer ProcedureTo compensatefor fuel and temperaturevariations
while performingthe idle mixture adjustment:a Do not idle engineover three minutesat a
c Recheckthe idle mixture adjustmentat thespecifiedrpm andadjustas required.If the idle mixtureadjustmentis not completedwithin threeminutes,repeatstepb.
2 Carefully remove idle limiter caps by installing a sheetmetal screw in center of cap and turningclockwise. A soldering gun may also be used to cutthrough plasticcaps.Discardthe caps.
3 Reset idle screws to the approximatepositionnoted beforethe limiter capswasremovedstep2.
NOTE: The tachometerusedshouldhavean expanded,scale of J00 to 800 or 0 to 1000 rpm. The instrumentshould be inspectedperiodically and calibrated to allownot morethan two percenterror.
NOTE: On all V-8 engineswith automatic transmissions, the throttle-stop solenoid is used to adjustcurbidle speed. Use the Jbllowing procedurefor idle speedad,justment.
a With solenoid wire connected,loosen solenoid locknut andturn solenoidin or out to obtain specified idle rpm.
b Tighten solenoidbracket.c Disconnect solenoid wire and adjust idle
6 Starting from full rich stop position as established before limiters was removed, turn mixturescrews clockwiseleaner until a loss of enginerpm isindicated.
7 Turn mixture screws counterclockwiseuntilthe highestrpm readingis obtained at lean best idlesetting. On carburetors incorporating two mixturescrews,turn both screwsequally unlessthe enginedemandsotherwise.
NOTE: If the idle speed changedmore than 30 rpmduring the mixture adjustment,reset to 30 rpm abovethe specifiedrpm and repeat theadjustment.
8 As a final adjustment, turn mixture screwsclockwiseuntil specifieddrop in enginerpm is obtained.
Engine Transmission Idle Drop
CJ-49 StateWithCatalyticConverter
304M
A
M
100---______
20
50CJAltitude
232,258A
-_______
25
304 M 100A ::: 20
CJ-California258 M 50
A--------
M:j__ 25
304 100A 20
Lean Best IdleNo Idle DropSpecified
CherokeeWagoneer,Truck-AllGeographicAreas
AllEngines
-
AllTransmissions
9 Install replacementblue service idle limitercapsover idle mixture screwswith limiter capearspositionedagainstthe full rich stops.Be carefulnot todisturb idle mixture setting while installing the caps.Presscapsfirmly andsquarelyinto place.
Infrared IR Analyzer Procedure-CJ Models with Six-Cylinder Engine Without Catalytic Converter
NOTE: Tocompensatefor fuel and temperaturevariations while performing theidle mixtureadjustment:
time.a Do not idle engineover three minutesat a
b If the idle mixture adjustmentis not completedwithin threeminutes,run engineat 2000 rpmforoneminute.
c Recheckthe idle mixture adjustmentat thespecifiedrpm and adjustas required.If the idle mixtureadjustmentis not completedwithin three minutes,repeatstep b.
NOTE: TheIR analyzerto beusedmustbeperiodicallyinspectedand calibrated to assureaccuratereadings.
1 ConnectIR analyzerby preciselyfollowing theinstructionsof the manufacturer.
7 If less than specified, turn screws counterclockwise1/16turn at atime, until specifiedCO readingis obtained.
8 If greaterthanspecified,turn screwsclockwiseuntil specified CO readingis obtained.
70485 9 Allow ten secondsfor meter to stabilizeaftereachadjustment.
70484
Idle Drop
thefollowing
to following
70486
4A-36 EMISSIONS CONTROLS - EXHAUST SYSTEMS
NOTE: If the idle speedchangedmore than 30 rpmduring the mixture adjustment,reset to the specifiedrpm and repeat the adjustmentuntil the specifiedcarbon monoxidelevel is obtained.
checked for free movementat the mileage intervalsspecified in the MechanicalMaintenanceSchedule.
Freecarburetorlinkage by applying JeepCarburetorand CombustionArea Cleaner,or equivalent.Neveruseoil to lubricatecarburetorlinkage.
For correct choke system adjustments, refer toFuel-Carburetionsectionof this manual.
Exhaust Manifold Heat ValveAn often overlooked,but highly importantemission
relatedcomponentis the exhaustmanifold heat valve.This valvecan affect thegasmileage,performance,driveability andespeciallyemissionlevels.
This valve is to be inspectedfor correctoperationandlubricated with JeepHeat Valve Lubricant, or equivalent, as outlined in the MaintenanceSchedule.Refer tothe ExhaustSection for serviceprocedures.
EXHAUST SYSTEMS
PageGeneral 4A-36
GENERALThebasic exhaustsystemon all vehiclesconsistsof a
front exhaustpipe, muffler, and tailpipe.All CJ modelsexcept49-statesix-cylindermodelsare
equippedwith a catalytic converter.Cherokee,Wagoneer and Truck models are equippedwith a catalyticconverterin California.
The exhaustsystemmust be properlyaligned to prevent stress, leakage, and grounding. If the systemgroundson anybodypanel, it mayamplify objectionablenoisesoriginating from the engineor the body. Wheninspectingan exhaustsystem,checkfor crackedor loosejoints, strippedbolt threads,andcorrosiondamage.Replace all partsthat are badly corrodedor damaged.Donot attemptto repair.
EXHAUST MANIFOLD HEAT VALVE
Six-Cylinder EngineA thermostaticallycontrolled heat valve in the ex
haust manifold directs exhaustheat to the floor of theintake manifold for rapid fuel vaporizationduringengine warmup. The valve directs exhaustheat to theintake manifold when the counterweightis in the extreme counterclockwiseposition when viewedfrom thecounterweightend fig. 4A-44. As the enginereachesoperatingtemperature,the thermostaticspringheatsupand loses tension, allowing counterweightto turn thevalve,directing heataway from the intakemanifoldfig.
PageExhaust Manifold Heat Valve 4A-36
Fig. 4A-44 Heat Valve in Heat-On Positlon-Slx-Cyllnder
The manifold heat valve must operate freely andshouldbe checkedand lubricatedwith JeepHeatValveLubricant,or equivalent,as outlined in the MaintenanceSchedule.
Replacement
1 Removeand separateintakeandexhaustmanifolds refer to SectionlA-Six-Cylinder Engine.
tweenthe right exhaustmanifold and exhaustpipe directs exhaustheat to the intakemanifold for rapid fuelvaporizationduringenginewarmup. Thevalve is c]osed,directing exhaust heat through the intake manifoldcrossoverpassagewhen thecounterweightis in thehorizontal position fig. 4A-46. The exhaustheat crossesthrough the intakemanifold anddischargesinto the leftexhaust manifold until the engine reachesoperatingtemperature.At this time, the thermostaticspring losesits tension and the counterweight moves downward,openingthe valve and allowing the exhaustheat to dischargethroughthe right exhaustpipe.
The manifold heat valve must operatefreely andshould le checkedand lubricatedwith JeepHeatValveLubricant,or equivalent,asoutlinedin the MaintenanceSchedule.
Replacement1 Disconnectandlower exhaustpipes.2 Replacewith manifold heatvalveandgaskets.3 Replaceexhaustpipe gaskets.4 Position exhaustpipes and connectto exhaust
NOTE: Timing and idle specifications are given for:* 49-State Applications 49* Altitude Compensation Applications ALT* California Applications CAL 70489
4A-40 EMISSIONS CONTROLS - EXHAUST SYSTEMS ri
Emission Components-CJ Models
49 State Vehicles
EngineClO
Venturis
Series Trans. Guard c: EGREGRCTOemp.
BPS FTVC PCV TCS Spark S kcroemp.
Carb.Vtst
Can.
I ThOttl Dashpot
232 i v2581V
CJ-5, CJ-7 M3 S - S 115° - S * M - 5 160° * - S -
CJ.7 A S - 5 115° - S S M - 5 160° 5 - - -
258 1V CJ-5, CJ-7 M4 S - 5 115° - I I M - I 160° 5 - * -
3042VCJ-5, CJ-7 M3 S S 5 115° - S S
-
S
V-
V
-
-
-
-
-
-
-
-
-
-
- - S
CJ-7 A *-
*-
5 115°-
- * - I -
Altitude Vehicles
232 1V2581V
CJ-5, CJ-7 M S S I 115° - S S M - 5 160° S - - -
CJ-7 A I S * 115° - I I M S * 160° * - - -
3042VCJ-5, CJ-7 M
A
*S
*-
S
5-
S
115° -
-
-
S *-
S
V-
V
-
-
S
I
S
160° -
-
-
* - -
CJ-7 115° S 160° S S -
California Vehicles
2581VCJ-5,CJ-7 M
A
S
S
S-
S
*-
5
115°
115°
-
-
-
S S-
I
M-
M
-
-
S
-
5
-
160°
S-
5
- S -
CJ-7 S - S -
3042VCJ-5, CJ-7 M
A
S
S
S-
I
I-
5
115°
115°
5.0-
-
S I-
I
V-
V
I-
I
5
5
160°
160°
-
-
- - S
CJ-7 S - I -
Non-Integral Type Back- Trans. - Transmission Type manual or automatic FTVC - Fuel Tank Vapor ControlPressure Sensor Cat. Cony. - Catalytic Converter TAC - Thermostatically Controlled Air
EGR - Exhaust Gas Recirculation Cleaner vacuum or mechanicalBPS - Back Pressure Sensor TCS - Transmission Controlled SparkPCV - Positive Crankcase Ventilation I - On all models in series specified
70490
1
49-State Vehicles
California Vehicles
_______________-
EMISSIONS CONTROLS - EXHAUST SYSTEMS 4A-4I
Emission Components-Cherokee, Wagoneer and Truck
Trans.. - Transmission Type manual or automatic FTVC - Fuel Tank Vapor ControlCat. Cony. - Catalytic Converter TAC - Thermostatically Controlled AirEGR - Exhaust Gas Recirculation Cleaner vacuum or mechanicalBPS -. Back Pressure Sensor TCS - Transmission Controlled SparkPCV - Positive Crankcase Ventilation S - On all models in series specified
Delay Valve
® Integral Back-Pressure/EG R Valve
70491
TECHNICAL BULLETIN REFERENCE
Date TB No. Subject Changes Information on Page No.