. ~ .·· ·}-. .-..

:
H(~l
-, ~ ..· .

•·, e EXHAUST.·.,
,._~
·-~·.
S-YSTEMS
SE.CTION INDEX •·. ·'"!
_,

P•g• - P~ge
Air lnJei:IIQn Systems 1K-7 . Exhaust Manifolds,: Mufflers and Pipes 1K-1
~
Catalytic Converter Systems 1K..13 _. ·

EXHAUST MANIFPLDs,·- . ,•' /

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MUFFLERS AND PIPES',: .. ·-.
... __ ...- Page Page
Exhaust Manifold Replacement 1K-4 Plpa Replacement 1K·6
General 1K-1 _-- _Restricted Exhaustsystem Diagnosis 1K-1

-----------------------
Exhaust Manlfoid Heal Valv'li · 1K-4 '. - ·-' · , · Specifications 1K-6
(j Muffler Replacement 1K-5

GENER~L
-,.,,,/'

. -loose joints, stripped screw threads, and corrosion dam-·

The b~sic exhaust system for ~ll J~~P vehi~les consists -
-- age, Inspect for ·worn. or;.
b:roken hangers. Replace all
.components that are ha!ilY: corroded or damaged. Do not
of exhaustma~if61d(s), .front exhaust'p\pe, catalytic con~_ ,. attinnpt to repair. - ·
yerter, .muffler and· tailpipe. --

NOTE: All reference to CJ vehicles includes Scramb~ RE,STRICTED EXHAUST SYSTEIV! DIAGNOSIS
vehicle~. '· - -,: .A restricted or blocked exha).lst system usually results
. . · in loss of power or backfire up through the carburetor.
CJ vehicles witll"four- or six-cylinder engines that are · Verify that the· condition is not caused by ignition tim-
designated 49:;S{ate use a conventional oxidizing cataly- : · ing or other ignition system ml;l:lfun~tions, then perform
tic (COC) pellet-type converter (fi'gs. 1K-1 and 1K-2). . a visualinspection of the exhaust system. If the ref!tric~
Four-cylind~r engine CJ vehicles manufactured for sale • ·, tion cann~t be located by visual inspection, perform t~e
in California use a three-way catalytic (TWC) pellet- •_following test procedure.- · ~ · -~i: .:
/type converter. Six-cylinder engine GJ vehicles manu~ · (1) Attach vacuum gauge to intake manifold.
factured for sale in California and all six-cylinder engine ·(2) ·coniJ,ect tachometer.
Cherokee, Wagoneer andTruck vehi~lesuse a dual bed- · · .-
. h "d ·WARNING: Usli 'eq;tr.eme caution when engine is oper~- .
(COC arid TWC) monolithic-type converter wit own- ..· b,ting. Do not stand in direct line with fan. Do no.t :P.ut
stream" air injection (figs. 1K.,;2 and 1K-3). .
·Eight-cylinder engine Cherokee, Wagoneer and Truck . hands near puU~ys, ·belts· or fan. Do not wear- lQbse
vehicles designated 49-State use a cqnventiona.l. O}{idiz~ · ":clothing;~. .. ' --
- ing catalytic (COC) pellet-type converter (fig.1K.:.4). · ,, .·. · · (a) Start erigit.1e and observe vacuum ga:_uge/Gauge
..The exhaust system must be properly aligned to pre-' · · should indicate 16 to'21 iiL Hg (54 to 71 kPa) ofvacuum.
')vent stress; leakage and c?assis conta~t. If ~he ~ystem (4) Increase engine speed to 2,000 rpm and observe
\ -/ contacts any body panel, 1t may amphfy obJectiOnable vacuum gauge. Vacuum will decrease when engine speed
. noises originating .from the engine or the body. When is_ increase(i rapidly, but should settle at 16 to 21 in. Hg
inspecting an exhau!jt system, inspect for cracked ·or (54 tci 7i kPa) and' remain steady. If vacuum decreases-
 HANGI5R MUFFLER
SUPPORT- HEAT
BRACKET - - - - . SHIELD

HANGER----.;....;.._,

INSULATOR·
BRACKET _ _ _,_,.
/
FLANGE

1. EXHAUST
. PIPE .

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MUFF~~R

CATALYTIC
CONVERTER 81193A

Fig. 1K-1 Four-Cylinder Engine Exhaust Sy~tem-CJ Vehicles

MUFFLER
HANGER _,__.....,....,..~··
.•.. HEAT
SIJPPORT. - SHIELD
~

/
. :· ,. BRACKEr
HANGER - - - - - - - '=

.... ·..
-~ . ;.. . .
.:~ ..
. ' : ·.
~N:l'J:lfR---.... 1d:t.. I

SPACER . i
CONVERTER ~
' HEAT SHIELD-----...

EXHAUST
PIPE

MUFFLER

CONVI:RTER
AIR INJECTION
- - - TUBE (CALIFORNIA
ONLY) 811938

Fig. 1K·2 Six-Cylinder Engine ExhausJ ·system~CJ Vehicles

 ·r • -~·;,·-~-.-~,..-. •. :..• ~ --• .. , ------.•--.• .-""!it--. .

~~ ~.,i".::j:j:;;t;r,f;~:~·:_,.:, ... , · ··• '· ·

l _./'
'l

I·
/'-~)\ ·~·
-:1..,
·-..---:~
..
.-'/: ' ,. ...
, .; '
' . . .
MANUAL .
TRANSMISSION
o·NI,.Y

·.CLEVIS[()\
PIN I W
v

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\
I'

1'1_.'\

REAR EXHAUST
PIPE (TRUCK ONL V)
81047A .
t .. - '

Fig. 1K~3 Six-Cylinder Engine Exhaust System"-Ch.rokae•Wagoneir~Truck

~·:

below 16 in. Hg (~4 kPa), exhaus.t system is restricted or

blocked; Stop engine and proceed to step (5). · ·
(5} Disconnect~xhaust pipe ·at manifold, · ·
(6) Start engine and increase speed to 2,000 rpm.
Observe vacuum gauge. ·
· · (a) If vacuum settles at 16 to 21 Hg (54 to 71 in.
kPa), restriction· or blockage is in exhaust pip~, catal;ytic
converter or muffler: . .. ... .•
(b}'If vacuuin decreases below 16 in. Hg (54
kPa) with exhaust pipe disconnected, exhaust man'ifold. NOTE: Do not use a Wire .err a light to ·inspect'ports:· :the·
is restricted. · · · ·· restricted opent'ng may be large enoug·h for wire or li{iht
(7) Co~riect exhaust pipe, remove mu,ffler, .start en- to pass through but small. enough to cause emcessive
gine and observe vacuum gauge. back pressure at kigh·eri{Jirie rpm.
· · · ·(a) If vacuum decreases below 16 in. Hg (54 ...
/·--,~,Pa), restriction or blo~~age is in cataly.ti~. converter: ... (12) Remove casting flash. If flash is at lower end o.f
/ ( ) \. ;. . (b) If vacu !1m 1s normal, muf~lEiris restr~cted. . port, it can usually be c.hipped out. If flash cannot be
removed, replace manifold.
1.. \ L ,OTE: ..if the converter has failed, always inspect the
· m1!ffier to det.ermine if converter debri;s has entered it; (13} Install exhaust manifold(s).
fKo.4 EXHAUST SYSTEMS

. (
' \
MANUAL
TRANSMISSION
ONLY
CLEVIS
PIN

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REAR EXHAUST
~··
PIPE (TRUCK ONL VI
81047~

Fig. 1K-4 Eight-Cylinder Engine Exhaust System-Cherokee-Wagoneer-Truck

EXHAUST MANIFOLD REPLACEMENT EXHAUST MANIFOLD HEAT VALVE

. Four• and six-cylinder engines are not equipped with
Four-Cylinder Engine heat valves.

The exhaust manifold is located on the left hand. side Eight-Cylinder Engine
of the engine (fig. lK-5). Refer to Chapter lB-Engines A thermostaticaJ~y contr~lled heat valve mounted be-
for replacem.e~t procedure~ tween tll:e- right exhaust manifol9 and exh~ust pipe di-
rects exhaust heat to the intake ma.~ifp)d f9r rapid fuel
Six~Cylinder· Engine vaporization du:t;ing engine warmup. When the counter-
·The intake and exhaust..manifolds are attached with weight is· in the. hor'izop.tal position; the. valve is in the
common bolts and n,~ts t!). the cy)inde~bead ~n theleft heat· On position, ·directing exhaust heat through th~
side of the engine. A gasket is used between the intake '.intake mapifqld crossov~r pa:ssage_.(fig~)~-7) .. The ex-
man,ifold· ~nd the cylinder head. No gasket is used be;... ·haust heat crosses through .the intake manifold and dis,.
tween the exhaust manifo~d and cylinder head or be- charges i-nto the left exhaust manifold untit.'the engine
tween exhaust manifold and exhaust pipe {f.ig. lK-6). attains normal operating temperature. At this time, the
Refer to Chapter lB-Engines for replacement heated bimetallic spring loses its tenr:iion, the counter-
procedure. weight mo.ves downward and the valve moves to the
heat Off position. This: EJ.llOwJ? .the .exhauat heat t.o dis-
Elght~Cyllnder Engine charge COtnP.~etely t}lrough 'the. right exhaust pipe.
Examine. · the manifold heat valve for freedom of ~
Refer to Chapter lB-Engines for replacement movement, and lubricate every 30,000 miles (48 000 km).· '""'
procedure. with Jeep Heat Valve Lub:ticant, or equivalent.
 EXHAUST SYSTEMS .· JK-5

INTAKE MANIFOLD
COOLANT
GASKET

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..: ·. TIGHTENING SEQUENCE .., : ...
9os&&'
. -~---..
Fig. lK-5 Exhaust Manifold-Four-Cylinder Engln~ 60116A
I '1
I f
.Replacement
(1) Disconne~t and lower exhaust pipe.
f'm·
(2) Replace manifold heat ~')ve and gasket. · ·
'1Qr
1 .
0
(3) Replace exhaust pipe gasket. ·
(4) Position exhaust pipe and connect to exhaus;t,
manifolds. · ·

MUFFLER REPLACEMENT
41887
Removal ..
TIGHTENING SEQUENCE

·,(p 'Remove front and rear ~uffler clamps.• Fig. 1K-6 Manifold Assambly-Six-Cyllndar Engine
· (2) ·Support ~eat of vehiCI~. by. side raiis .and allow
axle to hang free. . Installation
(3) ~Remove tailpipe hanger clamp. (1) Attach mU,ffler to tailpipe. Ensure l9cator on.
(4) Insert tool· between taUpipe and muf!ler at sev- tailpipe. aligns with slot in muffler.
eral,places to loosen pipe from muffler. , ·.
(2) Attach catalytic converter or rear exhaust pipe
. (5) Disconnect rear hanger, if equipped.· to muffler. Ensure pipe· has sufficient clearance from ·
floorpan. · ·
(6) Heat catalytic converter or rear exhaust pipe-to~
muffler joint with oxyacetylene torch until cherry red.
·- -~ .
(3) Install clamps and hangers.
. (7)
Place block of wood against front of muffler and
'j)
· · ----'drive muffler rearward to disengage. . (4) Start engine and inspect for exhaust leaks and
(8) Drive muffler off tailpipe. contact with body panels.
1K-6 EXHAUST SYSTEMS

COUNTERWEIGHT (3) Heat exhaust pipe-to-converter joint with oxya-

I cetylene torch until cherry red. Twist exhaust pipe back

and forth to disengage.

Installation
(1) ConneCt exh~ust pipe to converter.
(2) Cl!'lari mating surfaee(s),at manifold(s). Attach
exhaust pipe to manifold(s) but do not tighten. Use re-
placement gftsket(s) if necessary.
(3) Align e:x;haust pipe. Tighten clamp or mounting
bracket at rear of exhaust pipe. Tighten flal1ge(s) on
manifold(s).

Tailpipe
When replacing a tailpipe, support the vehicle with
80010 frame rails. ·

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Fig. lK-7 . Exhaust Manlfo_ld Heat Valva In
Heat On Position-Eight-Cylinder Engine Removal
To remove a tail pipe attached to the muffler, cutthe
PIPE· _REPLACEMENT pipe close to the muffler. Collapse the p1,1rt remaining in
the muffler and remove.
Front Exhaust Pipe
Installation
Removal
To install a tailpipe, disconnect the mounting bracket
(1) Disconnect exhaust pipe from manifold. and lower the front of the muffler. -Install the tail pipe.
(2) Disconnect mounting bracket and/or clamp. Position the mounting bracket and tighten.

SPECIFICATIONS
Torque Specifications
Service Set-To Torques should be used when assembling components. Service In-Use Recheck Torques should be used for checking a pre-tightened Item.

USA (ft.-lbs) Metric (N-m) .·

Service Service
Service· ln'Use Service ln•Uiie
Set-To Recheck Set-To Recheck
Torque Torque . Torque' torque
Exhaust Manifold Screws Four-Cylinder Engine .................................. . 37 34-40 50 47-53
Exhaust and Intake Manifold Screws and Nuts
Six-Cylinder Engine ..........................•................................ 23 18-28 31 24-38
Exhaust Manifold Screws -'Eight-Cylinder Engine
Center (2) ................................. , .. , , . , ..... , .. , .. , , , . , ........... ..
~~:~~.
25 34 27-41
Outer (4) ...............••........................•........................... 15' 20 20-34
Exhaust Pipe-to-Manifold Nuts ................................................. . 20 27 15-25 20-34

All torque values given in foot-pounds and newton-meters with dry fits unless otherwise specif_ied. 70295
 __EXHAUST SYSTEMS 1K~ 7

AIR INJECTION $YSTBMS

P•ge Page
Coolant Temperatura Switch Replacement_ 1K·12 , General 1K·7
-Downstream Air InJection Tuba Replacement 1K-13 Single Air InJection Srstam 1K-7
. D!lal Air InJection Srstalil 1K·11 -Specifications 1K·13
Dual Air InJection Srstam Dlagnosla '1K·12

GENERAL. AIR INJECTION

MANIFOLI) DIVERTER VALVE-
The basic air iiljection system for both ~ix- and eight;.: DIVERTER TO-AIR INJECTION
cylinder._ Jeep engines incorporates a belt-driverf air : YALVE MANIFOLD HOSE
pump, a vacuum_ controlled diverter (bypass)_ valve, air
injection :rnanifold(s) with chec~ valve(s) and connecting
. hoses (fi~.ll{-8 and lK-9); .-_. · ~- · · · · · ~-~ '
-u

NOTE: Four-cylinder Jee,p engines are not equipperJ,

.with an air injection system. .
Air is discharged from the 'aJr pump to the diverter

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valve, wpich either directs it tQ the air distribution
manifold(s) or vents it to the atmosphere through. a
bypass vent, depending ori angine. operating conditions'.
System air pressure is maintained at approximately 5
psi (35 kPa) by a relief valve-located :within the diverter.
valve assembly; .
(--1 Air is/outed through the air inje~tio~ m~nifold~s) into
, ./the engme exhaust port areas. The air ·!.mxes with hot
--- exhaust_•and promotes additional. burning of the mix~ DIVERTER
ture. Thjs reduce~ hydrocarbon and carbon monoxide VAI,.VE· TO·AIR . . .
_INJECTION· MANIFOLD HOSE 42006
emission to the atmpsphere. · · .-
· Fig. lK-9 Air InJection Sptam-Eight-Cyllndar Engine
T_here are two Air Systems used with. six-cylinder
·Jeep. engines, the- basic (single) air injection system
(used for 49-Sta.te CJ vehicles) and a. du~l air injection a
The dual air input is -c~mpri~ed .of belt driven air
. system (used for California CJ vehicles a.nd all Chero- pump, diverter valve, air conti'ol valve, divert and up-
kee, Wagoneer and Truck vehicles).. stream solenoids, reverse and two-way deiay valves,
coolant temperature switch, air injection manifold,
·_DIYERTER· "downstream" air injection tube and connecting hoses
VALVE· (fig. lK-10). The
· TO~AIR . . two
. .air inputs into the exhaust_
. system
. ' are:·
INJECTION
MANIFOLD . ' ·
HOSE • upstream air injection via the air injection manifold
attached to the exhaust manifold; ··
• downstream air injection to the dual bed (COC and
TWC) converter. · .

SINGLE AIR INJE~TIO" SYSTEM

·A!r Pump
The same air for botP,_six~ and eight-
AIR Pl!MP VACUUM HOSE; cylinder engines; of the air pump
FITTING ·
· are enclosed in a die1wcast ~tUC1nin housing. A filter fan·
430'40
. - - ... assembly, rotor shaft h-q.b are visible on the
Fig. lK·B Basic Air InJection Srstam::-Six-C,IInder Engine. pump e~terior (fig.lK-11)::,;:)
1K·B EXHAUST SYSTEMS

REVERSE DEl.,AY..>-<1 REAR COVE~

,......cTOVALVE ~- ~ij

VACUUM ~ ----------- ),_

SWITCH
ASSEMBLY
~~
~)~-- TWO-WAY DELAY
,ilf'V
a
\ . 11 MANIFOLD DIVERT _,Q
!.:\~. VACUUM SOLENOID ~
~ '\1 rr<(J SOURCE

~
11

[ UPSTREAM
"61 SOLENOID ·
o,®_j,;
. c-----
AIR INJECTION ~ ------------ ---~" .
MANIFOLD ~ ([)®__.- ~

\ ~(!JU(fl :~IR
~ - CONTROL
DIVERTER
VALVE
""'- CHECI< VALVE
VALVE

AIR PUMP-TO-
DIVERTERVALVE
HOUSING
o(})C@HOSE 42007
CHECK VALVE........._!"

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OJ ~UMP
Fig. 1K-11 Air Pump .
AIR INJECTION
TUBE TO CONVERTER...._ . 905998
of the pump housing. The rotor that ·drives the vanes
rotates . off the centerline of the pump housing. This
Fig. 1K-1 0 Dual Air System-Six-Cylinder Engine creates change13 in the· distance between the outside of
the rotor and the inner wall of the pump housing during
The pump is designed for long life and is serviceable rotor rotation. As the leading vane moves past the in-
only by replacement. Do not remove the rear housing take opening, it is moving from a small area to a large
cover for any reason. The internal components of the area. This creates a partial vacuum that forces air to
pump are not serviceable. enter the pump. As the vanes and rotor continue to
The aluminum housing has cavities for air intake, rotate, the trailing vane passes the intake and traps the
compression and exhaust and a bore for enclosing the air between the vanes. The vanes and rotor move the air
front bearing. The housing also includes cast metering into a smaller area to compress it. Compression contin-
areas that reduce the noise of intake and compression. ues until the leading vane passes the exhaust opening.
Mounting bosses are located on the housing exterior. There the compressed air passes out of the pUmp to be
NOTE: The pressure relief valve is located within the either distributed or vented.
diverter valve assembly. If defective, replace the di-
verter valve assembly. Noise Diagnosis
The front bearing supports the rotor shaft. The bear- The air pump is not completely noiseless. Under nor-
ing is secured in position by plastic injected around mal conditions, noise will rise in pitch as the engine
grooves in the housing and outer bearing race. speed. increases. Allow for normal break-in wear of the
The rear cover supports the vane pivot pin, rear inner pump prior to replacement for excessive noise.
bearing race and exhaust tube. Dowel pins pressed into A chirping or squeaking noise normally originateE
the housing correctly position the end cover, which is from vane rub in the housing bore and is noticeable a1
fastened by four screws. . low speed. intermittently. Vane chirping is often elimi·
The rotor positions and drives the two vanes. A nated at .increased pump speeds or with additional wear·
stamped steel liner supports the carbon shoes and shoe in time. A chirping noise may also be caused by the driv(
springs that seal the vanes and rotor. The two plastic belt slipping on the pulley of a seized pump.
vanes are molded to hubs that support the bearings, Bearing noise, a rolling sound noticeable at all
which rotate on the pivot pin. The pulley drive hub is speeds, is easily distinguished from vane chirping. I1
pressed onto the rotor shaft, and threaded holes in the does not necessarily indicate bearing failure. If bearing
hub provide for attachment of the pulley. noise reaches an objectionable level at certain speeds,
the pump may have to be replaced.
Operation Failure of a rear bearing is identified by a continuous
The pump vanes are located 180° apart and rotate knocking noise and replacement of the pump is
around the pivot pin, which is located on the centerline required.·
 . EXHAUST SYSTEMS 1K~9

Service Precautions Removal-Eight-Cylinder Engine

The following list of service precautions ~,tre for pre- (1) Disconnect air pump output hose at pump.
/~-) ·venting damage to the air pump. · (2) Loosen mount bracket-to-pump attaching screw
• Do not attempt to prevent the pulley from rotating and bolt. Remove drive belt. ·
by inserting tools into the centrifugal filter fan. (3) Remove pivot screw and brace screws.
• Do not operate an engine with the pump belt re- (4) Remove pump:
moved or disconnected except for noise diagnosis.
• Do not attempt to lubricate any part of the pump.
. • Do not clean the centrifugal filter~ Installation-Eight-Cylinder Engine
, • Do not dis~tssemble. the pump or remove the rear (1) Position pump it mounting location and install
cover.
pivot and brace attaching screws. Do not tighten.
• Do not exceed 20 foot-pounds (27 N•m) torque when
tightening the n:wunting bolts. . CAUTION: Adjust thebelt tension by hand only.
• Do not pry on the ah,1minum housing to adjust the (2) Install drive belt and'adjust to specified tension .
.• belt tension. (3) Tighten mounting screws a,nd ·adjusting strap
• Do not clamp the pump in a vise. screw with 20 foot-pounds (27 N•m) torque.
•.Do not permit liquids to enter the pump when steam ·'i

or water pressure-cleaning the engine.

Divorter (Bypass) Valvo· ...
Remo~ai-Six-Cyllnder Engine with V-Bells A diverter valve is used with all air inje~tion appli-

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(1) Disconnect air pump output hose at back of air cations. The valves for six- and eight-cylinder engines
pump . . differ only in the number of outlets. The six-cylinder
engine diverter valve has one outlet. The eight-cylinder
(2) Remove adjustment bolt and remove drive belt.
(3) Remove front mounting bracket. . engine diverter valve has two outlets. A high flow di-
(4) Remove adjustment bracketfrmn cylinder 4ead. verter valve is used on some applications where great~r' .
; (5) Slide pump from pivot stud. airflow is required for emission controL ·
The valve momentarily diverts air pump output from
the exhaust manifold(s) and vents it to the atmosphere
Installation-Six-Cylinder Engine with V-Bells during rapid deceleration. The valve also functions:a:s ;i:.;;·:;t.
pressure release valve for excessive air pump output. Ari ;,-:
(1) Slide pump onto pivot stud. · internal silencer is also incorporated in the diverte:r
(2) Install front moui}ting bracket. ... valve housing to muffle the airflow ... · -'"· ,,
(3) Install adjustment bracket and install adjust-
ment screw. '
Operation
CAUTION: Adjust thebelt tensionby hand only.
In a rapid decel~ration.situfl,ti~n; high' int~ke manifold
(4) Install drive belt and adjust to specified tension. vacuum· is applied to the dhiphragr:n in 'the diverter
Tighten pivot stud nut. valye. When. the v~cuum is20 in, Hg (68 kPa.) or. more,
(5) Connect air pump output hose to back of pump. the spring tension. of the diaphragm is overcome. This
moves the metering valve' dOwn a.gain~t its upper seat
Removal-Six-Cylinder Engine with Serpentine Ball and away from its:Io\Ver seat. This diverts and vents air,
pump 'outpufpressur~ to the atmosphere (fig. li(-J2).:·
(1) Release belt tension by loosening alternator ad- Air pumpoutput is diverted only momentarily because
justment and pivot bolts. of a vent hole in the diaphragm; This hole allowstatmos.;
(2) Disconnect air pump output hose from back of ph eric .pref;lsUre to quickly equalize on both sides of the
pump. diaphragm and the diaphragnl'spring returns the meter~
(3) Remove air pump mounting bolts/mits and air ingvalve toits normal position. · ·
pump. If the air pump develops exces$ive output pressure,
the excessive .pressllre overcomes t]:le diap}l,ragm spring
tension and pushes the,tri~tel'ing valv\=l down. Pump out-
lnslallation...,...Six-Cyllndar Engine with Serpentine Ball
put pressure is dive·rted and vented to'the atriwsphere.
(1) Position air pump arid secure with mounting When pump output pressure returns to normal, the me-
bolts/nuts. · · tering valve moves up from the upper seat and against
) (2) Connect O\ltput hose to back of pump .. the lower seat, returning to its normally ope-n-position.
j (3) Tighten .belt to specified tension. Refer to Chap- Pump output pressure is then directed to the exhaust
ter 1C-Cooling Systems for tension specification. manifold(s);:
1K~ 10 EXHAUST SYSTEMS

DIAPHRAGM
and air injection manifold(s). Removal involves dis-
DIAPHRAGM connecting the air hoses, vacuum hose and bracket
~SPRING clamp, if used. Installation entails connecting the air
hoses, vacuum hose and bracket clamp, if used.

Air InJection Manifolds

Air injection manifolds are constructed of cold-rolled
steel with zinc plating. They distribute air via the di-
verter valve from the air pump to each of the exhaust
manifold inlet ports.
AIR A check valve, incorporating a stainless steel spring

~=::j"'
OUTLET plunger and an asbestos seat, is integral with the air
injection manifold. Its function is to prevent the reverse
AIR flow of exhaust gas to the pump during pump or belt
INLET
(FROM failure, or diverter valve bypass operation. Reverse ex-
AIR haust gas flow would damage the air pump and con-
PUMP)
necting hoses.
The distribution tubes of the air injection manifold
are connected directly to the exhaust manifold. The hol-
low attaching fittings route airflow into the exhaust

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DIVERT AND
PRESSURE manifold inlet ports.
RELIEF OUTLET
(METERING
VALVE IN Check Valvo F;unclional Test
BYPASS
POSITION) A50277 To test the air injection manifold check valve for
proper operation, disconnect the air supply hose at the
Fig. 1K~ 12 Dllierter Valve-Typical · injection manifold. With the engine ope:ratirig above idle
speed, listen and feel for exhaust leakage from the check
Functional Test. valve. A slight leak is normal. .;

WARNING: Use extreme caution when engine is oper- Removal-Six-Cylinder Engine

ating. Do not stand in direct line with fan. Do not put (1) Disconnect air delivery hose at check valve.
hands near pulleys, belts or fan. Do not wear loose (2) Remove distribution tube fittings from exhaust
clothing. manifold inlet ports.
(1) Start engine and operate at idle. NOTE: Some resistance to turning may be encountered
(2) Examine diverter valve vent. Little or no air because of carbon build-up on the threads.
should floW from vent. · ·
(3) Accelerate· engine to 2000-3000 rpm and rapidly (3) Remove air injection manifold.
close throttle~ A strong flow of air should pass from
diverter valve vent for approximately three seconds. If Installation-Six-Cylinder Engine
air d0 es not flow ·or if engine backfire occurs, ensure (1) Connect air injection manifold with fittings to
vacuum hose has vacuum and there is no air leak. exhaust manifold. Tighten fittings with 20 foot-pounds
NOTE.: The diverter valve diverts and vents. air·pump (27 N•m) torque.
output when a manifold. vacuum·of20 in. Hg (68lcPa) or (2) Connect air delivery hose.
more is applied to the diaphragm. The diverter valve
also operates when pump output exceeds 5 psi (35 !cPa). Removal-Eight-Cylinder Engine
Some applications require 8 psi f55lcPa). (1) Disconnect air delivery hose at check valve.
(4) Slowly accelerate engine. Between 2500and 3500 (2) Remove distribution tube fittings from exhaust
rpm air should begin to flow from diverter valve vent. manifold inlet ports.
NOTE: Some r~sistance to turnfng may be encountered
Replacement because of carbon build-up on the threads.
The diverter valve is not serviceable and must be (3) Remove air injection manifold.
replaced if defective. The valve is either attached to a (4) Remove sealing gaskets. from air injection
bracket or suspended by the hoses between the air pump manifold. ·
 ' ,', '• EXHAUST SYSTEMS lKwll

NOTE: Duplicate the procedure for. the other air in- Upstream Solenoid
,/~\ jection manifold.
/ The air control valve circuit vacuum is controlled by
the "upstream" solenoid (mounted at the rear of the
Installation-Eight-Cylinder Engine cylinder head cover). The solenoid is grounded through
the feedback (CEC) system.
(1) Install air injection manifold using replacement When current is .allowed to flow through the circuit
sealing gasket on either side of each inlet port. and energize the "upstream" solenoid, it opens the air
(2) Install distribution tube fittings and injection control valve vacuum to the atmosphere and the air
· ma,nifold on exhaust manifold. Tighten fittings with 38 control valve directs system air pressure "upstream" to
foot-pounds (52 N•m) torque. the exhaust manifold. ··
(3) Connect air delivery hose to check valve. When the vacuum is allowed to pass through the "up-
NOTE: Duplicate the procedure for the o.ther air in- stream" solenoid (deenergized condition) to the air con-
.· jection manifold. trol valve, air system pressure is directed "downstream"
to the rear half of the dual bed catalytic converter.
;I·'

DUAlAIR INJECTION SYSTEM

Air Bypass Cir~ult Operation .
The additional components used with the dual air
injection system are:· The controlling Vll.CUUin for air bypass is regulated by
• divert and upstream solenoids, the divert solenoid, Open Loop 3 (OL3) vacuum switch

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· • air control valve, (CEC system) and two-way and reverse delay valves,
• coolant temperature switch,
• reverse and two-way delay valves, Divert Solenoid
• downstream air injection tuhe. · The:. divert solenoid is grounded via the feedback
NOTE: Diverter valve and air pump operation. ivith the (CEC) system. ·
·dual air injection system is basically, the ~.ame as it is When current flows through the circuit, the energized
) with thesingle air injection system. ·. · solenoid allows atmospheric pressure to displace the
' '
. . . ,
''
vacuum, which allows the diverter (bypass) valve to
NOTE: The dual air Vn;j'ection system is inter-related release system air pressure to the atmosphere:
with the feedback system and must. be diagnosed in
conjunction with the feedback system. Refer to Chapter
JJ-Fuel Systems: · ·
Two-Way and Reverse De!ay Valves·
Two-way and reverse delay valves are n,sed to prevent-
'
Air Control Circuit Operation a sudden loss of vacuum dU,ring a rapid vacuum decrease _
·.. ·. caused by engine accelera,tion.

Air ControfValva · Coolant Temperature Switch

Tli~ air control valve is located between the diverter
The coolant temperature switch is located at the rear·
valve and the ·air injection manifold. The air control
of the intake manifold. This switch controls the up-
valve is controlled by vacuum regulated by the upstream
stream solenoid operation. ·
solenoid.
The air control valve directs system air pressure ei- NOTE: 'l,'he coolant switch (dual junction) also pro-
ther "upstream" (into the air injection manifold at- vides a ground-for the intake manifold heater.
tached to the exhaust manifold) when vacuum is applied
to it or "downstream" (directly into the dual bed mon-
Operation
olithic-type converter) when vacuum is not applied to it.
The air mixes with the hot exhaust when it enters the Manifold vammm should be present at the air control
"upstream" input and causes a further burning of the valve via the upstream solenoid when the coolant tem-
mixture. This reduces hydrocarbons (HC) and carbon perature is lower than 160°F (7l°C) (approximately) and
monoxide (CO) emission to the atmosphere. should not be present if the coolant temperature is above
During "downstream" operation, the additional air 160°F (71 oc) (approximately). If the coolant. temper-
) reacts with hydrocarbons (HC) and carbon monoxide ature is lower than 160°F (71 °C) and vacuum is not
(CO) in the catalytic converter (rear half) to create car- present, inspect the vacuum hoses for air leaks and
bon dioxide (C02) and water vapor and reduce undesi~ proper routing. Repair as necessary. If no fault is found,
rable emission into the atmosphere. replace the switch or microprocessor.
'1 K-12 EXHAUST SYSTEMS

DUAL AIR INJECTION SYSTEM DIAGNOSIS Air Control Circuit

General NOTE: Engine must be at normal operating

temperature.
The dual air injection system should be diagnosed in
conju•nction With the CEC System. Refer to Chapter Functional 'fest
1J-Fuel Systems.
(1) Disconnect air hoses from ports A and B of air
control valve. Hose A is connected to air injection mani-
Dive~ter Valve fold. Hose B is connected to catalytic converter.
WARNING: Use extreme caution when engine is oper-
Test the .diverter valve as outlined in Single Air In- ating. Do not stand in direct line with fan. Do not put
jection System Components. hands near pulleys, belts or fan. Do not wear loose
clothing.
NOTE: If the engine is at normal operating temper- (2) Start engine and warm to normal operating
ature, manifold vacuum will}j,[lve to be.}emporarily temperature . Turn ignition off.
connected to the valve during the test beca)u'se the con- (3) Restart engine and increase speed to 1500 rpm.
trol val'l!f circuit wUl be i'YI, operation. Air should exhaust from port A of air control valve for
approximately 30 seconds, then exhaust from port B.

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(a) If no air exhausts, inspect diverter valve
Air Bypass Circuit vents for air exhaust.
1. If air is exhausted, with engine at 1500
rpm, determine if vacuum is being applied to diverter
Functional Test valve.
2. If vacuum is present, replace diverter
... (1) .Disconnect air hoses from ports A and B of air
valve and retest.
control valve. Hose A is connected to air injection mani-
3. If vacuum is not present, refer to Chap-
fold. Hose B is connected to catalytic converter.
ter 1J-Fuel Systems and test divert solenoid.
WARNING: Use extreme caution when engine is oper- 4. If air is not exhausted, inspect air pump
ating. Do not stand in direct line with fan. Do not put for proper operation. .
hands near pulleys, belts or fan. Do not w.ear loose (b) If air exhausts from both ports, replace air
clothing. control valve and retest system.
(c) If air exhausts only from port B, remove
(2) Start engine and warm t6 normal operating
temperature. Turn ignition off.' · ·· · · vacuum hose and check for vacuum during first 30 sec-
onds of operation. •· ·.
(3) Restart engine and increase speed to 1500 rpm.
1. If vacuum is not present, replace air con-
Air should exhaust from port A of air control valve for
trol valve and retest.
approximately 30 seconds, then exhaust.fromport B.
2. If vacuum is present, refer to Chapter
(a) If no air exhausts, inspect diverter valve
1J-Fuel Systems and test upstream solenoid.
vents for air exhaust.
. . · (d)· If air exha'llst is normal, de~;ess acce~erator
1. If aJr is being exhausted,int;rease engine
pedal to floor, .return· engine to idle and mspect drverter
speed to 1500 ·rpm and determine. if vacuum is being
valve vents for air exhaust.
applied to diverter valve.
1. If air is exhausted, system is operating
2. If vacuum is present, replace diverter
normally.
valve and retest. If no vacuum is present, refer to Chap·
2. If air is ,not. exhausted, ch~ck diverter
ter 1J-Fuel Systems and test divert solenoid.
valve vacuum hose for vacuum. If no vacuum, replace
3. If air is not being exhausted, inspect air
diverter valve. If vacuum is present, refer to Chapter
pump for proper operation. .
1J-Fuel Systems and test divert solenoid. ·
(b) If air exhaust from air c'ontrol valve is nor-
mal, depress accelerator pedal to floor, return engine to
idle and inspect diverter valve 've:hts for air exhaust.
COOLANT TEMPEA~TURE SWITCH REP.LACEMENT
1. If air is exhausted, circuit is operating
normally. WARNING: Serious. burns can result if hot coolant is
not drained before removing the switch from the intake
2. If air is not exhausted, check diverter
valv:e vacuum hose for ·vacuum; If no vacuum, replace manifold. ,,
diverter valve. If vacuum is present, refer to Chapter (1)· Drain coolant from radiator.
1J-Fuel Systems and test divert solenoid. (2) Disconnect wire connector.
 EXHAUST SYSTEMS 1K-13

(3) Use open-end wrench to remove switch from NOTE: It may be necessary to heat the joint for
intake manifold. removal.
(4) Install replacement v~lve in intake manifold.
(5) Connect wire connector.
, . (6) Install coolant and purge air from cooling sys- (3) Attach injection tube to catalytic converter
tem, Refer to Chapter lC-Cooling Systems. nipple.
( 4) Install check valve, if removed, and tighten with
DOWNSTREAM AIR INJECTION TUBE REPLACEMENT 25 foot~pounds (34 N•m) torque minimum.
(1) Disconnect air delivery hose at check valve.
(5) Connect air delivery hose to check valve.
NOTE: Remove check valve if it is to be reused.
(6) Install clamp to secure "downstream" air in-
(2) Remove clamp connecting "downstream" air in- jection tube to catalytic converter nipple. Tighten clamp
jection tube to catalytic converter nipple. with 3 to 4 foot-pounds (4 to5 N•rri) torque. · ·

SPECIFICATIONS
Torque Specifications

Service Set-To Torques should be used when a$embling components. Service In-Use Recheck Torques should be uSed for checking a pre-tightened item.

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USA (ft.-lbs) Metric (N-m)

Service Service
Service In-Use Service ln-U~;e
Set-To Recheck Se~,To Recheck
Torque Torque Torque Torque
Air Pump Mounting Screws ..................... , .. , ......................... , .. 20 15-22 27. 20-30 ·.. ··.
Air Injection Manifold Fittings
Six-Cylinder Engine ....... : . .............. , .................................. . 20 15-22 . 27 20-27
Eight-Cylinder Engine .......................................................... . 38 30-45. . - 5~. 41-61
()
\ All Torque values given in foot-pounds and newton-meters with dry fits unless otherwise specified:· 70296

CATALYTIC CONVERTER
SYSTEMS
Page Page
Catalyst Replacement 1K-14 General 1K-13
Conventional Oxidizing Catalytic (COC) Pellet-Type Converter 1K-13 Three-Way Catalytic (TWC) Pellet-Type Converter 1K-14
Dual Bed (COC and TWC) Monolithic-Type Converter 1K-14 Tools 1K-16

GENERAL for sale in California- use a dual bed (COC ~nd TWC).
monolithic-type converter with "downstream.:' air
NOTE: All reference to CJ vehicles also pertains to injection.
Scrambler vehicles.
. . - CAUTION: The use of leaded fuel destroys catalytic
All CJ vehicles with four-cylinder engines utilize a converters and oxygen sensors.
pellet-type catalytic converter to reduce undesirable ex-
All Jeep vehicles· are designed for unleaded fuel and
haust gas emissions. Vehicles designated 49-State use a.
are equipped with a fuel filler neck restrictor that pre-
conventional oxidizing catalytic (COC) converter_apd ve-
vents the insertion of the larger leaded fuel-filler hose
hicles designated for sale in California use a three-way nozzle. -
catalytic (TWC) converter. There is no scheduled
maintenance required for either type converter. CONVENTIONAL OXIDIZING CATALYTIC (CDC) _
A GOC pellet-type catalytic converter is used with all PELLET·TYPE CONVERTER -.
eight-cylinder engine exhaust systems, All Cherokee,
Wagoneer and Truck vehicles with six-cylinder engines . The pellet-type conventional oxidizing ·catalytic
and CJ vehicles with six-cylinder engines manufactured (COC) converter contains beads of alumina coated with
 1K·14 EXHAUST SYSTEMS

platinum and palladium catalyzing agents. Thousands rear half is a conventional oxidizing catalytic (COC)
of pellets are contained in a steel canister. A plug is converter. The front half is a three-way catalytic (TWC)
provided in the converter to permit replacement of the converter.
pellets should they become ineffective. As with the TWC pellet-type converter (above), main-
taining high conversion efficiency for this type con-
This type converter promotes the oxidation of in-
verter requires that the carburetor provide an air/fuel
completely burned fuel (HC) and carbon monoxide (CO).
mixture ratio of approximately 14.7:1 (fig. 1K-18). This
The chemical process involved changes HC and CO into
is the primary function of the Feedback System used in
harmless carbon dioxide (C02) and water (H20) vapor
conjunction with the converter.
before the exhaust gas is emitted into the atmosphere.
The catalysts that cause the chemical changes are plati- co
num and palladium.
With ·pellet-type COC converters, all exhaust gases
100
w~
-~~
/!'~ ~
flow through the catalytic converter.
80
The temperature inside a converter is somewhat
higher than the temperature of the exhaust gases when
RICH
~
~ LEAN
~
they are exhausted from the engine. Insulation in the 60
pellet-type converter keeps the outside skin of the con- CONVEASION ~
verter at approximately the same temperature as the EFFICIENCY % ~
~

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muffler. Because of its larger mass, the converter stays 40
hot much longer than the muffler. ~
~
~
The steel catalytic converter body is designed to last 20 ~
the ·life of the vehicle. Excessive heat can result in bul- ~
ging or other distortion, but excessive heat will not be ~
~
the fault of the converter. A carburetor, air pump or 0 ~
13:1 14:1 14.7:1 16:1 16:1
ignition problem that permits unburned fuel to enter the
converter will usually cause overheating. If a converter 90996
is heat-damaged, the carburetor, air pump, or ignition Fig. 1K-13 Optimum Alr/Fual Ratio for Conversion EHiclancw
problem should .be corrected at the same time the con-
verter is replaced. All other components of the exhaust
system should also be inspected for heat damage. CATALYST REPLACEMENT

THREE-WAY CATALYTIC (TWC) PELLET·TYPE CONVERTER Dual Bed (CDC and TWC) Monolithic·Type Converter
This type converter is not serviceable. The entire unit
This type converter utilizes rhodium in addition to must be replaced if defective. Remove by disconnecting
platinum and palladium as oxidizing agents. Rhodium is the air injection tube and detaching converter from the
a catalyst for oxides of nitrogen (NOx) and changes it front exhaust pipe and the muffler (or rear .exhaust pipe,
and carbon monoxide (CO) into nitrogen (N2) and carbon ifequipped). Install replacement converter.
dioxide (C02); ·
Operationally, as the air/fuel mixture is leaned out,
the converter efficiency for changing HC and CO is CDC and TWC Pellet-Type Converter
increased but is decreased for changing NOx. Enrichen-
ing the mixture increases converter efficiency for chang- The pressed-in plug must be removed to replace the
ing NO:x but decreases it for HC and CO. For this reason, pellets. A replacement plug (fig. 1K·14) is required to
to optimize the simultaneous conversion of all three, the seal the converter after the pellets have been replaced.
carburetor must pr()vide ~n air/fuel mixture ratio of On-vehiele · servicing is the only factory approved
approximately 14.7:1 (fig. 1K-13). This is the primary method of replacing pellets because catalytic converters
function of the C4 System that is used in .conjunction are difficult to remove from most vehicles, especially
with the Three-Way Catalytic (TWC) Converter. after a large nuinber· of miles have accumulated, with~
out damaging the converter assembly or exhaust
connections. ·
DUAL BED (CDC AND TWC) MONOLITHIC·TYPE CONVERTER The catalyst replacement tool includes an emptying 1

and fill mechanism, a vacuum aspirator and two hand

The dual bed monolithic-type converter used with six- tools used for removal of the converter drain plug. The
cylinder engines is two converters in one container. The emptying and fill mechanism clamps directly to the
 EXHAUST SYSTEMS 1K-15

CONVERTER (3) Connect air hose (80 psi minimum) to fitting on

HOUSING vacuum aspirator.

/· .. NOTE:.· Vacuum aspirator must be in· operation prior to

removing plug to prevent pellets from spilling out. on
·shop floor.

CAUTION: Use care to prevent damaging converter

housing when removing plug. If the drain-fill hole can-
.not be se.aled with the replacement plug, the converter
must be replaced.

(4) Remove·plug from bottom of converter with re-

moval tools provided with Tool Kit J-25077-01.
(5) Clamp container-vibrator unit (using Adapter J-
25077-6) onconverter (fig. 1K-16).
(6) Remove air hose from vacuum aspirator.
(7) Connect air hose (80 psi or 550 kPa minimum) to
fitting on vibrator. Approximately ten minutes is re-

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quired to empty pellets from converter.
80432 (8) Disconnect air. hose, remove contamer ana ms-
card pellets. · ·
Fig. 1K-14 COC and TWC Pellet-Type Converter Plug
(9) Fill container with replacement pellets and at-
catalytic converter and consists of an· air turbine vibra~ tach to converter.
tor unit and discharge-fill container. The vibrator in- (10) Connect air hose (80 psi or 550 kPa minimum) to
duces a rotary motion to the catalytic converter case fitting on vacuum aspirator. Pellets will be forced into
causing the catalyst pellets to flow out the drain po:rt · converter and packed in place.
and into the attached container. NOTE: If any pellets pass through the converter and
An adapter is included to adapt the exchanger to the· into the tailpipe, the converter is defective and must be
newer-type converters, which have an unthreaded, replaced.
(pressed-in) access plug.
(1) Raise vehicle.
(2) Clamp vacuum aspirator (part of Tool J-25077-
01) on tailpipe outlet (fig. 1K-15).

VIBRATOR

\
)
A43046

Fig. 1K-15 Vacuum Aspirator Fig. 1K-16 Container-Unit VIbrator

1K~.16 EXHAUST SYSTEMS

(11) When full of pellets, remove container-vibrator (b) Insert s~rew through washer and plug.
unit from converter. Maintain air pressure at vacuum
aspirator. (c) Carefully thread screw into bridge and
(12) Plug converter with replacement plug (fig. 1K- tighten sufficiently to create an air-tight seal.
15).
(a) Thread screw into bridge and position (13) Disconnect air hose from fitting on vacuum as-
bridge inside opening. Remove screw without disturbing pirator. Remove vacuum aspirator from tailpipe. Lower
bridge position. vehicle

Tools

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J-25077
CATALYTIC CONVERTER
CATALYSTCHANGE.R

70462