JEEP CHEROKEE 1994 Service Repair Manual

(12) Properly position the distributor rotor as fol-
lows:
(a) Remove No.1 spark plug. Hold your finger
over the spark plug hole and rotate the crankshaft
until compression pressure is felt. Slowly continue
to rotate the crankshaft until the timing index on
the vibration damper aligns with the top dead cen-
ter (TDC) mark (0É on the timing degree scale).Al-
ways rotate the crankshaft clockwise (the
direction of normal rotation). DO NOT rotate
the crankshaft backward to align the timing
marks.
(b) Rotate the oil pump gear so that the gear slot
on the oil pump shaft is slightly past the 3 o'clock
position (Fig. 12). A flat blade screwdriver can be
used to rotate the gear.
(c) Turn the distributor shaft until the rotor tip
points in the direction of No.1 terminal in the dis-
tributor cap. Turn the rotor 1/8 turn counterclock-
wise past the position of No.1 terminal.
(d) With the distributor cap removed, start the
distributor into the cylinder block with the rotor lo-
cated at the 5 o'clock position (Fig. 13).
(e) Slide the distributor shaft down into the en-
gine. Position the distributor vacuum advance
mechanism housing in approximately the same lo-
cation as when removed. Align the scribe mark onthe distributor housing with the corresponding
scribe mark on the cylinder block. The rotor should
align with the position of No.1 terminal when the
distributor shaft is down in place. It may be neces-
sary to rotate the oil pump shaft with a long flat-
blade screwdriver to engage the oil pump drive
tang.
(f) Install the distributor holddown clamp and
bolt. DO NOT tighten the bolt.
(g) When the distributor is fully engaged in its
correct location, the rotor should be at the 6 o'clock
position (Fig. 14).
(h) If the distributor is not properly installed, or
if it is removed later, then the complete installa-
tion procedures must be repeated.
(13) Install the radiator or radiator/condenser, if
equipped with A/C.
(14) Fill the cooling system.
(15) Connect negative cable to battery.
Fig. 11 Timing Case Cover
Fig. 12 Oil Pump Gear Slot Alignment
Fig. 13 Distributor Rotor Pre-Positioning
Fig. 14 Correct Rotor Position
9 - 30 2.5L ENGINEJ

CAMSHAFT PIN REPLACEMENT
REMOVAL
WARNING: DO NOT LOOSEN THE RADIATOR
DRAIN COCK WITH THE SYSTEM HOT AND PRES-
SURIZED BECAUSE SERIOUS BURNS FROM COOL-
ANT CAN OCCUR.
(1) Disconnect negative cable from battery.
(2) Drain the radiator. DO NOT waste reusable
coolant. Drain the coolant into a clean container.
(3) Remove the fan and shroud.
(4) Disconnect the radiator overflow tube, radiator
hoses, automatic transmission fluid cooler pipes (if
equipped).
(5) Remove the radiator.
(6) If equipped with air conditioning:
CAUTION: DO NOT loosen or disconnect any air
conditioner system fittings. Move the condenser
and receiver/drier aside as a complete assembly.
(a) Remove the A/C compressor serpentine drive
belt idler pulley.
(b) Disconnect and remove the generator.
(c) Remove the A/C condenser attaching bolts
and move the condenser and receiver/drier assem-
bly up and out of the way.
(7) Remove the serpentine drive belt.
(8) Remove the crankshaft vibration damper.
(9) Remove the timing case cover. Clean the gas-
ket material from the cover.
(10) Rotate crankshaft until the crankshaft
sprocket timing mark is closest to and on the center
line with the camshaft sprocket timing mark (Fig.
15).
(11) Remove camshaft sprocket retaining bolt.
(12) Remove the crankshaft oil slinger.
(13) Remove the sprockets and chain as an assem-
bly (Fig. 16).CAUTION: The following procedural step must be
accomplished to prevent the camshaft from damag-
ing the rear camshaft plug during pin installation.
(14) Inspect the damaged camshaft pin.
(15) If the pin is a spring-type pin, remove the bro-
ken pin by inserting a self-tapping screw into the pin
and carefully pulling the pin from the camshaft.
(16) If the pin is a dowel-type pin, center-punch it.
Ensure the exact center is located when center-
punching the pin.
CAUTION: Cover the opened oil pan area to prevent
metal chips from entering the pan.
(17) Drill into the pin center witha4mm(5/32
inch) drill bit.
(18) Insert a self-tapping screw into the drilled pin
and carefully pull the pin from the camshaft.
CAMSHAFT BEARINGS
The camshaft rotates within four steel-shelled, bab-
bitt-lined bearings that are pressed into the cylinder
block and then line reamed. The camshaft bearing
bores and bearing diameters are not the same size.
They are stepped down in 0.254 mm (0.010 inch) in-
crements from the front bearing (largest) to the rear
bearing (smallest). This permits easier removal and
installation of the camshaft. The camshaft bearings
are pressure lubricated.
It is not advisable to attempt to replace cam-
shaft bearings unless special removal and instal-
lation tools are available.
Camshaft end play is maintained by the load
placed on the camshaft by the oil pump and distrib-
utor drive gear. The helical cut of the gear holds the
camshaft sprocket thrust face against the cylinder
block face.
Fig. 15 Timing Chain Alignment
Fig. 16 Camshaft and Crankshaft Sprocket and
Chain
J2.5L ENGINE 9 - 31

INSTALLATION
(1) Clean the camshaft pin hole.
(2) Compress the center of the replacement spring
pin with vise grips.
(3) Carefully drive the pin into the camshaft pin
hole until it is seated.
(4) Install the camshaft sprocket, crankshaft
sprocket and timing chain with the timing marks
aligned (Fig. 15).
(5) To verify correct installation of the timing
chain, turn the crankshaft to position the camshaft
sprocket timing mark as shown in Fig. 17. Count the
number of chain pins between the timing marks of
both sprockets. There must be 20 pins.
(6) Install the crankshaft oil slinger.
(7) Tighten the camshaft sprocket bolt to 108 Nzm
(80 ft. lbs.) torque.
(8) Check the valve timing.
(9) Coat both sides of the replacement timing case
cover gasket with gasket sealer. Applya3mm(1/8
inch) bead of Mopar Silicone Rubber Adhesive Seal-
ant, or equivalent to the joint formed at the timing
case cover and cylinder block.
(10) Position the timing case cover on the oil pan
gasket and the cylinder block.
(11) Place Timing Case Cover Alignment and Seal
Installation Tool 6139 in the crankshaft opening of
the cover (Fig. 18).
(12) Install the timing case cover-to-cylinder block
bolts. Install the oil pan-to-timing case cover bolts.
(13) Tighten the 1/4 inch cover-to-block bolts to 7
Nzm (60 in. lbs.) torque. Tighten the 5/16 inch front
cover-to-block bolts to 22 Nzm (192 in. lbs.) torque.
Tighten the oil pan-to-cover 1/4 inch bolts to 14 Nzm(120 in. lbs.) torque. Tighten the oil pan-to-cover 5/16
inch bolts to 18 Nzm (156 in. lbs.) torque.
(14) Remove the cover alignment tool and install a
replacement oil seal into the cover.
(15) Install the vibration damper on the crank-
shaft.
(16) Lubricate and tighten the damper bolt to 108
Nzm (80 ft. lbs.) torque.
(17) If equipped with air conditioning:
(a) Install the A/C compressor serpentine drive
belt idler pulley.
(b) Install the generator.
(c) Install the A/C condenser and receiver/drier
assembly.
(18) Install the serpentine drive belt on the pulleys
and tighten (refer to Group 7, Cooling System for the
specifications and procedures).
(19) Install the radiator. Connect the radiator
hoses and automatic transmission fluid cooler pipes,
if equipped. Fill the cooling system.
(20) Install the fan and shroud.
(21) Connect negative cable to battery.
OIL PAN
REMOVAL
(1) Disconnect negative cable from battery.
(2) Raise the vehicle.
(3) Remove the oil pan drain plug and drain the
engine oil.
(4) Disconnect the exhaust pipe at the engine ex-
haust manifold.
(5) Disconnect the exhaust hanger at the catalytic
converter and lower the pipe.
(6) Remove the engine starter motor.
(7) Remove the flywheel/torque converter housing
access cover.
(8) Position a jack stand directly under the engine
vibration damper.
Fig. 17 Verify Crankshaft/Camshaft Installation
Fig. 18 Timing Case Cover Alignment and Seal
Installation Tool 6139
9 - 32 2.5L ENGINEJ

(9) Place a piece of wood (2 x 2) between the jack
stand and the engine vibration damper.
(10) Remove the engine mount through bolts.
(11) Using the jack stand, raise the engine until
adequate clearance is obtained to remove the oil pan.
(12) Remove the oil pan bolts. Carefully remove
the oil pan and gasket.
CLEANING
Clean the block and pan gasket surfaces.
INSTALLATION
(1) Fabricate 4 alignment dowels from 1 1/2 x 1/4
inch bolts. Cut the head off the bolts and cut a slot
into the top of the dowel. This will allow easier in-
stallation and removal with a screwdriver (Fig. 1).
(2) Install two dowels in the timing case cover. In-
stall the other two dowels in the cylinder block (Fig.
2).
(3) Slide the one-piece gasket over the dowels and
onto the block and timing case cover.
(4) Position the oil pan over the dowels and onto
the gasket.(5) Install the 1/4 inch oil pan bolts. Tighten these
bolts to 14 Nzm (120 in. lbs.) torque. Install the 5/16
inch oil pan bolts (Fig. 3). Tighten these bolts to 18
Nzm (156 in. lbs.) torque.
(6) Remove the dowels. Install the remaining 1/4
inch oil pan bolts. Tighten these bolts to 14 Nzm (120
in. lbs.) torque.
(7) Lower the engine until it is properly located on
the engine mounts.
(8) Install the through bolts and tighten the nuts.
(9) Lower the jack stand and remove the piece of
wood.
(10) Install the flywheel/torque converter housing
access cover.
(11) Install the engine starter motor.
(12) Connect the exhaust pipe to the hanger and to
the engine exhaust manifold.
(13) Install the oil pan drain plug (Fig. 3). Tighten
the plug to 34 Nzm (25 ft. lbs.) torque.
(14) Lower the vehicle.
(15) Connect negative cable to battery.
(16) Fill the oil pan with engine oil to the specified
level.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A DI-
RECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR FAN. DO
NOT WEAR LOOSE CLOTHING.
(17) Start the engine and inspect for leaks.
OIL PUMP
The positive-displacement gear-type oil pump is
driven by the distributor shaft, which is driven by a
gear on the camshaft. Oil is siphoned into the pump
through an inlet tube and strainer assembly that is
pressed into the pump body.
The pump incorporates a nonadjustable pressure
relief valve to limit maximum pressure to 517 kPa
Fig. 1 Fabrication of Alignment Dowels
Fig. 2 Position of Dowels in Cylinder Block
Fig. 3 Position of 5/16 inch Oil Pan Bolts
J2.5L ENGINE 9 - 33

(75 psi). In the relief position, the valve permits oil
to bypass through a passage in the pump body to the
inlet side of the pump.
Oil pump removal or replacement will not affect
the distributor timing because the distributor drive
gear remains in mesh with the camshaft gear.
REMOVAL
(1) Drain the engine oil.
(2) Remove the oil pan.
(3) Remove the pump-to-cylinder block attaching
bolts. Remove the pump assembly with gasket (Fig.
4).
CAUTION: If the oil pump is not to be serviced, DO
NOT disturb position of oil inlet tube and strainer
assembly in pump body. If the tube is moved within
the pump body, a replacement tube and strainer as-
sembly must be installed to assure an airtight seal.
INSTALLATION
(1) Install the oil pump on the cylinder block using
a replacement gasket. Tighten the short bolt to 14
Nzm (10 ft. lbs.) torque and the long bolt to 23 Nzm
(17 ft. lbs.) torque.
(2) Install the oil pan.
(3) Fill the oil pan with oil to the specified level.
OIL PUMP PRESSURE
The MINIMUM oil pump pressure is 89.6 kPa (13
psi) at 600 rpm. The MAXIMUM oil pump pressure
is 255-517 kPa (37-75 psi) at 1600 rpm or more.
PISTONS AND CONNECTING RODS
REMOVAL
(1) Remove the engine cylinder head cover.
(2) Remove the rocker arms, bridges and pivots.
(3) Remove the push rods.
(4) Remove the engine cylinder head.
(5) Position the pistons one at a time near the bot-
tom of the stroke. Use a ridge reamer to remove the
ridge from the top end of the cylinder walls. Use a
protective cloth to collect the cuttings.
(6) Raise the vehicle.
(7) Drain the engine oil.
(8) Remove the oil pan and gasket.
(9) Remove the connecting rod bearing caps and
inserts. Mark the caps and rods with the cylinder
bore location. The connecting rods and caps are
stamped with a two letter combination (Fig. 1).
(10) Lower the vehicle until it is about 2 feet from
the floor.
CAUTION: Ensure that the connecting rod bolts DO
NOT scratch the crankshaft journals or cylinder
walls. Short pieces of rubber hose, slipped over the
rod bolts will provide protection during removal.
(11) Have an assistant push the piston/connecting
rod assemblies up and through the top of the cylinder
bores (Fig. 2).
INSPECTIONÐCONNECTING ROD
CONNECTING ROD BEARINGS
Inspect the connecting rod bearings for scoring and
bent alignment tabs (Figs. 3 and 4). Check the bear-
ings for normal wear patterns, scoring, grooving, fa-
tigue and pitting (Fig. 5). Replace any bearing that
shows abnormal wear.
Fig. 4 Oil Pump Assembly
Fig. 1 Stamped Connecting Rods and Caps
9 - 34 2.5L ENGINEJ

Inspect the connecting rod journals for signs of
scoring, nicks and burrs.
CONNECTING RODS
Misaligned or bent connecting rods can cause ab-
normal wear on pistons, piston rings, cylinder walls,
connecting rod bearings and crankshaft connecting
rod journals. If wear patterns or damage to any of
these components indicate the probability of a mis-
aligned connecting rod, inspect it for correct rod
alignment. Replace misaligned, bent or twisted con-
necting rods.
BEARING-TO-JOURNAL CLEARANCE
(1) Wipe the oil from the connecting rod journal.(2) Use short rubber hose sections over rod bolts
during installation.
(3) Lubricate the upper bearing insert and install
in connecting rod.
(4) Use piston ring compressor to install the rod
and piston assemblies. The oil squirt holes in the
rods must face the camshaft. The arrow on the piston
crown should point to the front of the engine (Fig. 6).
Verify that the oil squirt holes in the rods face the
camshaft and that the arrows on the pistons face the
front of the engine.
(5) Install the lower bearing insert in the bearing
cap. The lower insert must be dry. Place strip of
Fig. 2 Removal of Connecting Rod and Piston
Assembly
Fig. 3 Connecting Rod Bearing Inspection
Fig. 4 Locking Tab Inspection
Fig. 5 Scoring Caused by Insufficient Lubrication or
by Damaged Crankshaft Pin Journal
Fig. 6 Rod and Piston Assembly Installation
J2.5L ENGINE 9 - 35

Plastigage across full width of the lower insert at the
center of bearing cap. Plastigage must not crumble
in use. If brittle, obtain fresh stock.
(6) Install bearing cap and connecting rod on the
journal and tighten nuts to 45 Nzm (33 ft. lbs.)
torque. DO NOT rotate crankshaft. Plastigage will
smear, resulting in inaccurate indication.
(7) Remove the bearing cap and determine amount
of bearing-to-journal clearance by measuring the
width of compressed Plastigage (Fig. 7). Refer to En-
gine Specifications for the proper clearance.Plasti-
gage should indicate the same clearance across
the entire width of the insert. If the clearance
varies, it may be caused by either a tapered
journal, bent connecting rod or foreign material
trapped between the insert and cap or rod.
(8) If the correct clearance is indicated, replace-
ment of the bearing inserts is not necessary. Remove
the Plastigage from crankshaft journal and bearing
insert. Proceed with installation.
(9) If bearing-to-journal clearance exceeds the spec-
ification, install a pair of 0.0254 mm (0.001 inch) un-
dersize bearing inserts. All the odd size inserts must
be on the bottom. The sizes of the service replace-
ment bearing inserts are stamped on the backs of the
inserts. Measure the clearance as described in the
previous steps.
(10) The clearance is measured with a pair of
0.0254 mm (0.001 inch) undersize bearing inserts in-
stalled. This will determine if two 0.0254 mm (0.001
inch) undersize inserts or another combination is
needed to provide the correct clearance (refer to Con-
necting Rod Bearing Fitting Chart).FOR EXAMPLE:If the initial clearance was
0.0762 mm (0.003 inch), 0.025 mm (0.001 inch) un-
dersize inserts would reduce the clearance by 0.025
mm (0.001 inch). The clearance would be 0.002 inch
and within specification. A 0.051 mm (0.002 inch)
undersize insert would reduce the initial clearance
an additional 0.013 mm (0.0005 inch). The clearance
would then be 0.038 mm (0.0015 inch).
(11) Repeat the Plastigage measurement to verify
your bearing selection prior to final assembly.
(12) Once you have selected the proper insert, in-
stall the insert and cap. Tighten the connecting rod
bolts to 45 Nzm (33 ft. lbs.) torque.
Fig. 7 Measuring Bearing Clearance with Plastigage
CONNECTING ROD BEARING FITTING CHART
9 - 36 2.5L ENGINEJ

SIDE CLEARANCE MEASUREMENT
Slide snug-fitting feeler gauge between the con-
necting rod and crankshaft journal flange. Refer to
Engine Specifications for the proper clearance. Re-
place the connecting rod if the side clearance is not
within specification.
PISTON FITTING
MICROMETER METHOD
(1) Measure the inside diameter of the cylinder
bore at a point 58.725 mm (2-5/16 inches) below top
of bore.
(2) Measure outside diameter of the piston. Be-
cause pistons are cam ground, measure at right an-
gle to piston pin at center line of pin (Fig. 8).
The difference between cylinder bore diameter and
piston diameter is piston-to-bore clearance.
FEELER GAUGE METHOD
(1) Remove the rings from the piston.
(2) Insert a long 0.025 mm (0.001 inch) feeler
gauge into the cylinder bore.
(3) Insert the piston, top first, into cylinder bore
alongside the feeler gauge. With entire piston in-
serted into cylinder bore, the piston should not bind
against feeler gauge.
(4) Repeat steps with a long 0.051 mm (0.002 inch)
feeler gauge. The piston should bind.
(5) If the piston binds on 0.025 mm (0.001 inch)
feeler gauge, the piston is too large or cylinder bore
is too small. If the piston does not bind on 0.051 mm
(0.002 inch) feeler gauge, the piston is too small for
cylinder bore. Pistons up to 0.102 mm (0.004 inch)undersize may be enlarged by knurling or shot-peen-
ing. Replace pistons that are 0.102 mm (0.004 inch)
or more undersize.
PISTON PIN
REMOVAL
Piston pins are press-fitted into the connecting rods
and require no locking device.
(1) Position the piston and connecting rod assem-
bly on an arbor press.
(2) Apply force to a piloted driver and press the
pin completely out of the connecting rod and piston
assembly (Fig. 9). Note position of the pin through
the gauge window of removal support tool.
INSPECTION
(1) Inspect the piston pin and pin bore in the con-
necting rod for nicks and burrs. Remove as neces-
sary. Never reuse a piston pin after it has been
installed in and removed from a connecting rod.
(2) With the pin removed from the piston and con-
necting rod, clean and dry piston pin bores and the
replacement piston pin.
(3) Position the piston so that the pin bore is in
vertical position. Insert the pin in bore. At room tem-
perature, the replacement pin should slide com-
pletely through the pin bore in piston by force of
gravity.
(4) Replace piston if pin jams in the pin bore.
INSTALLATION
(1) Insert the piston pin pilot through the piston
and connecting rod pin bores. Ensure that the arrow
on the piston crown is pointing up (Fig. 10).
Fig. 8 Piston Dimensions
Fig. 9 Piston Pin Removal/Installation
J2.5L ENGINE 9 - 37

(2) Position the pin pilot, piston and connecting
rod on a support with the squirt hole of the connect-
ing rod to the left-hand side (Fig. 10).
(3) Insert piston pin through the upper piston pin
bore and into the connecting rod pin bore.
(4) Position the piloted driver inside the piston pin
(Fig. 9).
(5) Using an arbor press, press the piston pin
through the connecting rod and piston bores until pin
pilot indexes with mark on the support. The piston
pin requires a 8 900 N (2,000 pounds) press-fit. If lit-
tle effort is required to install piston pin in a con-
necting rod, or if the rod moves laterally on the pin,
the connecting rod must be replaced.
(6) Remove the piston and connecting rod assembly
from the press. The pin should be centered in the
connecting rod (60.792 mm or60.0312 inch) and
float in the piston pin bore.
PISTON RING FITTING
(1) Carefully clean the carbon from all ring
grooves. Oil drain openings in the oil ring groove and
pin boss must be clear. DO NOT remove metal from
the grooves or lands. This will change ring-to-groove
clearances and will damage the ring-to-land seating.
(2) Be sure the piston ring grooves are free of
nicks and burrs.
(3) Measure the ring side clearance with a feeler
gauge fitted snugly between the ring land and ring
(Fig. 11). Rotate the ring in the groove. It must move
freely around circumference of the groove.
(4) Place ring in the cylinder bore and push down
with inverted piston to position near lower end of the
ring travel. Measure ring gap with a feeler gauge fit-
ting snugly between ring ends (Fig. 12). The correct
compression ring end gap is 0.25-0.51 mm (0.010-
0.020 inch). The correct oil control ring end gap is
0.381-1.397 mm (0.015-0.055 inch).
(5) Install the oil control rings according to in-
structions in the package. It is not necessary to use atool to install the upper and lower rails. Insert oil
rail spacer first, then side rails.
(6) The two compression rings are different and
cannot be interchanged. The top ring (Fig. 13) is a
moly ring (the scraping edge is gray in color). The
second ring (Fig. 14) is a black cast iron ring (the
scraping edge is black in color when new). The com-
pression rings may also be identified by 1 or 2 dots
on the top surface of the ring (Figs. 13 and 14).
(7) The second compression ring (black cast iron)
has a chamfer on the BOTTOM of the inside edge
(Fig. 15). This ring may also have 2 dots located on
the top surface.
(8) Using a ring installer, install the second com-
pression ring with the chamfer facing down (Fig. 16).
The two dots will be facing up.
Fig. 10 Correct AlignmentÐPiston and Connecting
Rod
Fig. 11 Ring Side Clearance Measurement
Fig. 12 Ring Gap Measurement
9 - 38 2.5L ENGINEJ

(9) The top compression ring (the scraping edge is
gray in color) has a chamfer on the TOP of the inside
edge (Fig. 15). This ring may also have 1 dot located
on the top surface.
(10) Using a ring installer, install the top ring with the
chamfer facing up (Fig. 16). The dot will be facing up.
(11) Position the gaps on the piston (Fig. 17):
²Oil spacer - Gap on center line of piston pin bore.
²
Oil rails - Gap 180É apart on centerline of piston skirt.
²No. 2 Compression ring - Gap 180É from top oil rail gap.
²No. 1 Compression ring - Gap 180É from No. 2
compression ring gap.
Fig. 13 Top Compression Ring Identification
Fig. 14 Second Compression Ring Identification
Fig. 15 Compression Ring Chamfer Location
Fig. 16 Compression Ring Installation
Fig. 17 Ring Gap Position
J2.5L ENGINE 9 - 39