JEEP CHEROKEE 1995 Service Repair Manual

Fig. 4 Oil Lubrication System
9 - 80 4.0L ENGINEJ

OIL PUMP
A gear-type oil pump is mounted at the underside
of the cylinder block opposite the No.4 main bearing.
The pump incorporates a nonadjustable pressure
relief valve to limit maximum pressure to 517 kPa
(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.
5).
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 bolts 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 in-
serts. 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 and con-
necting 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-
Fig. 5 Oil Pump Assembly
Fig. 1 Stamped Connecting Rods and Caps
J4.0L ENGINE 9 - 81

ings for normal wear patterns, scoring, grooving, fa-
tigue and pitting (Fig. 5). Replace any bearing that
shows abnormal wear.
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.
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
9 - 82 4.0L ENGINEJ

(5) Install the lower bearing insert in the bearing
cap. The lower insert must be dry. Place strip of Plas-
tigage across full width of the lower insert at the cen-
ter 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 mate-
rial 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 isneeded 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) un-
dersize 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
J4.0L ENGINE 9 - 83

SIDE CLEARANCE MEASUREMENT
Slide snug-fitting feeler gauge between the connect-
ing rod and crankshaft journal flange. Refer to En-
gine Specifications for the proper clearance. Replace
the connecting rod if the side clearance is not within
specification.
PISTON FITTING
BORE GAUGE METHOD
(1) To correctly select the proper size piston, a cyl-
inder bore gauge, Special Tool 6879 or equivalent, ca-
pable of reading in .00019INCREMENTS with gauge
ring Special Tool 6884 is required. If a bore gauge is
not available, do not use an inside micrometer.
(2) Set the bore gauge to the gauge ring and zero
gauge.
(3) Remove gauge from ring and check cylinder as
shown in (Fig. 8) bore and record reading.
(4) Measure the inside diameter of the cylinder
bore at a point 58.725 mm (2-5/16 inches) below top
of bore. Start perpendicular (across or at 90 degrees)
to the axis of the crankshaft at point B and then take
an additional bore reading 90 degrees to that at point A.
(5) Recheck bore gauge in gauge ring, bore gauge
should read zero. If gauge does not read zero, reset
gauge and start over with procedure.
The coated pistons will be serviced with the piston
pin and connecting rod pre-assembled.The coated
piston connecting rod assembly can be used to
service previous built engines and MUST be re-
placed as complete sets.Tin coated pistons should
not be used as replacements for the new coated pistons.
The coating material is applied to the piston after
the final piston machining process. Measuring the
outside diameter of a coated piston will not provide
accurate results. Therefore, measuring the inside di-
ameter of the cylinder bore with a dial Bore Gauge is
MANDATORY. To correctly select the proper sizepiston, a cylinder bore gauge capable of reading
.00019increments is required.
Piston installation into the cylinder bore requires
slightly more pressure than that required for non-
coated pistons. The bonded coating on the piston will
give the appearance of a line-to-line fit with the cyl-
inder bore.
PISTON PIN
Piston pins are press-fitted into the connecting rods
and require no locking device. The piston, piston pin
and connecting rod are replaced as an assembly.
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).
Fig. 8 Bore Gauge
Fig. 9 Piston Size Chart
Fig. 10 Piston Dimensions
9 - 84 4.0L ENGINEJ

(5) Install the oil control rings according to instruc-
tions in the package. It is not necessary to use a tool
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. 15).
The two dots will be facing up.
(9) The top compression ring (the scraping edge is
gray in color) has a chamfer on the TOP of the insideedge (Fig. 15). This ring may also have 1 dot located on
the top surface.
Fig. 16 Compression Ring Installation
Fig. 13 Top Compression Ring Identification
Fig. 14 Second Compression Ring Identification
Fig. 15 Compression Ring Chamfer Location
Fig. 11 Ring Side Clearance Measurement
Fig. 12 Ring Gap Measurement
J4.0L ENGINE 9 - 85

(10) Using a ring installer, install the top ring with
the chamfer facing up (Fig. 16). The dot will be fac-
ing up.
(11) Position the gaps on the piston (Fig. 17):
²Oil spacer - Gap on center line of piston pin bore.
²Oil 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.
CLEANING
Clean the cylinder bores thoroughly. Apply a light
film of clean engine oil to the bores with a clean lint-
free cloth.
INSTALLATION
(1) Install the piston rings on the pistons if re-
moved.
(2) Lubricate the piston and rings with clean en-
gine oil.
CAUTION: Ensure that connecting rod bolts DO
NOT scratch the crankshaft journals or cylinder
walls. Short pieces of rubber hose slipped over the
connecting rod bolts will provide protection during
installation.(3) Use a piston ring compressor to install the con-
necting rod and piston assemblies through the top of
the cylinder bores (Fig. 18).
(4) Ensure the arrow on the piston top points to
the front of the engine (Fig. 18).
(5) Raise the vehicle.
Each bearing insert is fitted to its respective jour-
nal to obtain the specified clearance between the
bearing and the journal. In production, the select fit
is obtained by using various-sized, color-coded bear-
ing inserts as listed in the Connecting Rod Bearing
Fitting Chart. The color code appears on the edge of
the bearing insert. The size is not stamped on inserts
used for production of engines.
The rod journal is identified during the engine pro-
duction by a color-coded paint mark on the adjacent
cheek or counterweight toward the flange (rear) end
of the crankshaft. The color codes used to indicate
journal sizes are listed in the Connecting Rod Bear-
ing Fitting Chart.
When required, upper and lower bearing inserts of
different sizes may be used as a pair (refer to Con-
necting Rod Bearing Fitting Chart). A standard size
insert is sometimes used in combination with a 0.025
mm (0.001 inch) undersize insert to reduce clearance
0.013 mm (0.0005 inch).
CAUTION: DO NOT intermix bearing caps. Each
connecting rod and bearing cap are stamped with
the cylinder number. The stamp is located on a ma-
chined surface adjacent to the oil squirt hole that
faces the camshaft side of the cylinder block.
(6) Install the connecting rod bearing caps and in-
serts in the same positions as removed.
CAUTION: Verify that the oil squirt holes in the rods
face the camshaft and that the arrows on the pis-
tons face the front of the engine.
(7) Install the oil pan and gaskets as outlined in
the installation procedure.
Fig. 17 Ring Gap Position
Fig. 18 Rod and Piston Assembly Installation
9 - 86 4.0L ENGINEJ

(8) Lower the vehicle.
(9) Install the engine cylinder head, push rods,
rocker arms, bridges, pivots and engine cylinder head
cover.
(10) Fill the crankcase with engine oil.
CRANKSHAFT MAIN BEARINGS
REMOVAL
(1) Disconnect negative cable from battery.
(2) Remove the spark plugs.
(3) Raise the vehicle.
(4) Remove the oil pan and oil pump.
(5) Remove only one main bearing cap and lower
insert at a time (Fig. 1).
(6) Remove the lower insert from the bearing cap.
(7) Remove the upper insert by LOOSENING (DO
NOT REMOVE) all of the other bearing caps. Now
insert a small cotter pin tool in the crankshaft jour-
nal oil hole. Bend the cotter pin as illustrated to fab-
ricate the tool (Fig. 2). With the cotter pin tool in
place, rotate the crankshaft so that the upper bear-
ing insert will rotate in the direction of its locking
tab. Because there is no hole in the No.3 main jour-
nal, use a tongue depressor or similar soft-faced tool
to remove the bearing insert (Fig. 2). After moving
the insert approximately 25 mm (1 inch), it can be
removed by applying pressure under the tab.
(8) Using the same procedure described above, re-
move the remaining bearing inserts one at a time for
inspection.
INSPECTION
Wipe the inserts clean and inspect for abnormal
wear patterns and for metal or other foreign material
imbedded in the lining. Normal main bearing insert
wear patterns are illustrated (Fig. 3).
If any of the crankshaft journals are scored,
remove the engine for crankshaft repair.
Inspect the back of the inserts for fractures, scrap-
ings or irregular wear patterns.
Inspect the upper insert locking tabs for damage.
Replace all damaged or worn bearing inserts.
FITTING (CRANKSHAFT INSTALLED)
The main bearing caps, numbered (front to rear)
from 1 through 7 have an arrow to indicate the for-
Fig. 1 Removing Main Bearing Caps and Lower
Inserts
Fig. 2 Removing Upper Inserts
Fig. 3 Main Bearing Wear Patterns
J4.0L ENGINE 9 - 87

ward position. The upper main bearing inserts are
grooved to provide oil channels while the lower in-
serts are smooth.
Each bearing insert pair is selectively fitted to its
respective journal to obtain the specified operating
clearance. In production, the select fit is obtained by
using various-sized color-coded bearing insert pairs
as listed in the Main Bearing Fitting Chart. The
bearing color code appears on the edge of the insert.
The size is not stamped on bearing inserts used
for engine production.
The main bearing journal size (diameter) is identi-
fied by a color-coded paint mark on the adjacent
cheek. The rear main journal, is identified by a color-
coded paint mark on the crankshaft rear flange.
When required, upper and lower bearing inserts of
different sizes may be used as a pair. A standard size
insert is sometimes used in combination with a 0.025
mm (0.001 inch) undersize insert to reduce the clear-
ance by 0.013 mm (0.0005 inch).Never use a pair
of bearing inserts with greater than a 0.025 mm
(0.001 inch) difference in size (Fig. 4).
When replacing inserts, the odd size inserts
must be either all on the top (in cylinder block)
or all on the bottom (in main bearing cap).
Once the bearings have been properly fitted, pro-
ceed to Crankshaft Main BearingÐInstallation.
BEARING-TO-JOURNAL CLEARANCE (CRANKSHAFT
INSTALLED)
When using Plastigage, check only one bearing
clearance at a time.
Install the grooved main bearings into the cylinder
block and the non-grooved bearings into the bearing
caps.
Install the crankshaft into the upper bearings dry.
Place a strip of Plastigage across full width of the
crankshaft journal to be checked.
Install the bearing cap and tighten the bolts to 108
Nzm (80 ft. lbs.) torque.
DO NOT rotate the crankshaft. This will
cause the Plastigage to shift, resulting in an in-
accurate reading. Plastigage must not be per-
mitted to crumble. If brittle, obtain fresh stock.Remove the bearing cap. Determine the amount of
clearance by measuring the width of the compressed
Plastigage with the scale on the Plastigage envelope
(Fig. 5). Refer to Engine Specifications for the proper
clearance.
Plastigage should indicate the same clearance
across the entire width of the insert. If clearance var-
ies, it may indicate a tapered journal or foreign ma-
terial trapped behind the insert.
If the specified clearance is indicated and there are
no abnormal wear patterns, replacement of the bear-
ing inserts is not necessary. Remove the Plastigage
from the crankshaft journal and bearing insert. Pro-
ceed to Crankshaft Main BearingÐInstallation.
If the clearance exceeds specification, install a pair
of 0.025 mm (0.001 inch) undersize bearing inserts
and measure the clearance as described in the previ-
ous steps.
The clearance indicatewith the 0.025 mm (0.001
inch) undersize insert pair installed will determine if
this insert size or some other combination will pro-
vide the specified clearany.
FOR EXAMPLE:If the clearance was 0q762 mm
(0.003 inch) originally, a pair of 0.0254 mm (0.001
inch) undersize inserts would reduce the clearance by
0.0254 mm (0.001 inch). The clearance would then be
0.0508 mm (0.002 inch) and within the specification.
A 0.051 mm (0.002 inch) undersize bearing insert
and a 0.0254 mm (0.001 inch) undersize insert would
reduce the original clearance an additional 0.0127
mm (0.0005 inch). The clearance would then be
0.0381 mm (0.0015 inch).
CAUTION: Never use a pair of inserts that differ
more than one bearing size as a pair.
FOR EXAMPLE:DO NOT use a standard size up-
per insert and a 0.051 mm (0.002 inch) undersize
lower insert.
Fig. 4 Bearing Insert Pairs
Fig. 5 Measuring Bearing Clearance with Plastigage
9 - 88 4.0L ENGINEJ

If the clearance exceeds specification using a pair
of 0.051 mm (0.002 inch) undersize bearing inserts,
measure crankshaft journal diameter with a mi-
crometer. If the journal diameter is correct, the
crankshaft bore in the cylinder block may be mis-
aligned, which requires cylinder block replacement or
machining to true bore.
Replace the crankshaft or grind to accept the ap-
propriate undersize bearing inserts if:
²Journal diameters 1 through 6 are less than
63.4517 mm (2.4981 inches)
²Journal 7 diameter is less than 63.4365 mm
(2.4975 inches).
Once the proper clearances have been obtained,
proceed to Crankshaft Main BearingÐInstallation.
MAIN BEARING JOURNAL DIAMETER (CRANKSHAFT
REMOVED)
Remove the crankshaft from the cylinder block (re-
fer to Cylinder Block - Disassemble).
Clean the oil off the main bearing journal.
Determine the maximum diameter of the journal
with a micrometer. Measure at two locations 90É
apart at each end of the journal.
The maximum allowable taper and out of round is
0.013 mm (0.0005 inch). Compare the measured di-
ameter with the journal diameter specification (Main
Bearing Fitting Chart). Select inserts required to ob-
tain the specified bearing-to-journal clearance.
Install the crankshaft into the cylinder block (refer
to Cylinder Block - Assemble and Crankshaft Main
Bearings - Installation).
INSTALLATION
(1) Lubricate the bearing surface of each insert
with engine oil.
(2) Loosen all the main bearing caps. Install the
main bearing upper inserts.
(3) Install the lower bearing inserts into the main
bearing caps.
(4) Install the main bearing cap(s) and lower in-
sert(s).
(5) Tighten the bolts of caps 1, 2, 4, 5, 6, and 7 to
54 Nzm (40 ft. lbs.) torque. Now tighten these bolts to
95 Nzm (70 ft. lbs.) torque. Finally, tighten these
bolts to 108 Nzm (80 ft. lbs.) torque.
(6) Push the crankshaft forward and backward.
Load the crankshaft front or rear and tighten cap
bolt No.3 to 54 Nzm (40 ft. lbs.) torque. Then tighten
to 95 Nzm (70 ft. lbs.) torque and finally tighten to
108 Nzm (80 ft. lbs.) torque.
(7) Rotate the crankshaft after tightening each
main bearing cap to ensure the crankshaft rotates
freely.
(8) Check crankshaft end play. Crankshaft end
play is controlled by the thrust bearing which is
flange and installed at the No.2 main bearing posi-
tion.(a) Attach a magnetic base dial indicator to the
cylinder block at either the front or rear of the en-
gine.
(b) Position the dial indicator rod so that it is
parallel to the center line of the crankshaft.
(c) Pry the crankshaft forward, position the dial
indicator to zero.
(d) Pry the crankshaft forward and backward.
Note the dial indicator readings. End play is the
difference between the high and low measurements
(Fig. 6). Correct end play is 0.038-0.165 mm
(0.0015-0.0065 inch). The desired specifications are
0.051-0.064 mm (0.002-0.0025 inch).
(e) If end play is not within specification, inspect
crankshaft thrust faces for wear. If no wear is ap-
parent, replace the thrust bearing and measure
end play. If end play is still not within specifica-
tion, replace the crankshaft.
If the crankshaft was removed, install the crank-
shaft into the cylinder block (refer to Cylinder Block -
Assemble).
(9) Install the oil pan.
(10) Install the drain plug. Tighten the plug to 34
Nzm (25 ft. lbs.) torque.
(11) Lower the vehicle.
(12) Install the spark plugs. Tighten the plugs to
37 Nzm (27 ft. lbs.) torque.
(13) Fill the oil pan with engine oil to the full
mark on the dipstick level.
(14) Connect negative cable to battery.
REAR MAIN OIL SEALS
The crankshaft rear main bearing oil seal consists
of two half pieces of viton with a single lip that ef-
fectively seals the rear of the crankshaft. Replace the
upper and lower seal halves as a unit to ensure leak-
free operation.
Fig. 6 Crankshaft End Play Measurement
J4.0L ENGINE 9 - 89