1988 JEEP CHEROKEE length

using ridge reamer. DO NOT remove an excessive amount of material.
Ensure ridge is completely removed.
PISTON & CONNECTING ROD REMOVAL
Note top of piston. Some pistons may contain a notch, arrow
or be marked "FRONT". Piston must be installed in proper direction to
prevent damage with valve operation.
Check that connecting rod and cap are numbered for cylinder
location and which side of cylinder block the number faces. Proper cap
and connecting rod must be installed together. Connecting rod cap must
be installed on connecting rod in proper direction to ensure bearing
lock procedure. Mark connecting rod and cap if necessary. Pistons must
be installed in original location.
Remove cap retaining nuts or bolts. Remove bearing cap.
Install stud protectors on connecting rod bolts. This protects
cylinder walls from scoring during removal. Ensure proper removal of
ridge. Push piston and connecting rod from cylinder. Connecting rod
boss can be tapped with a wooden dowel or hammer handle to aid in
removal.
PISTON & CONNECTING ROD
Disassembly
Using ring expander, remove piston rings. Remove piston pin
retaining rings (if equipped). On pressed type piston pins, special
fixtures and procedures according to manufacturer must be used to
remove piston pins. Follow manufacturer's recommendations to avoid
piston distortion or breakage.
Cleaning
Remove all carbon and varnish from piston. Pistons and
connecting rods may be cleaned in cold type chemical tank. Using ring
groove cleaner, clean all deposits from ring grooves. Ensure all
deposits are cleaned from ring grooves to prevent ring breakage or
sticking. DO NOT attempt to clean pistons using wire brush.
Inspection
Inspect pistons for nicks, scoring, cracks or damage in ring
areas. Connecting rod should be checked for cracks using Magnaflux
procedure. Piston diameter must be measured in manufacturers specified
area.
Using telescopic gauge and micrometer, measure piston pin
bore of piston in 2 areas, 90 degrees apart. This is done to check
diameter and out-of-round.
Install proper bearing cap on connecting rod. Ensure bearing
cap is installed in proper location. Tighten bolts or nuts to
specification. Using inside micrometer, measure inside diameter in 2
areas, 90 degrees apart.
Connecting rod I.D. and out-of-round must be within
specification. Measure piston pin bore I.D. and piston pin O.D. All
components must be within specification. Subtract piston pin diameter
from piston pin bore in piston and connecting rod to determine proper
fit.
Connecting rod length must be measured from center of
crankshaft journal inside diameter to center of piston pin bushing
using proper caliper. Connecting rods must be the same length.
Connecting rods should be checked on an alignment fixture for bent or
twisted condition. Replace all components which are damaged or not
within specification.
PISTON & CYLINDER BORE FIT

Fig. 18: Measuring Connecting Rod Side Clearance - Typical
This Graphic For General Information Only
Check for improper bearing installation, wrong bearing cap
or insufficient bearing clearance if side clearance is insufficient.
Connecting rod may require machining to obtain proper clearance.
Excessive clearance usually indicates excessive wear at crankshaft.
Crankshaft must be repaired or replaced.
MAIN & CONNECTING ROD BEARING CLEARANCE
Plastigage Method
Plastigage method may be used to determine bearing clearance.
Plastigage can be used with an engine in service or during reassembly.
Plastigage material is oil soluble.
Ensure journals and bearings are free of oil or solvent.
Oil or solvent will dissolve material and false reading will be
obtained. Install small piece of Plastigage along full length of
bearing journal. Install bearing cap in original location. Tighten
bolts to specification.
CAUTION: DO NOT rotate crankshaft while Plastigage is installed.
Bearing clearance will not be obtained if crankshaft is
rotated.
Remove bearing cap. Compare Plastigage width with scale on
Plastigage container to determine bearing clearance. See Fig. 19.
Rotate crankshaft 90 degrees. Repeat procedure. this is done to check
journal eccentricity. This procedure can be used to check oil
clearance on both connecting rod and main bearings.

length of cylinder block at several points.
If warpage exceeds specifications, deck must be resurfaced.
If warpage exceeds manufacturer's maximum tolerance for material
removal, replace block.
DECK HEIGHT
Distance from the crankshaft centerline to the block
deck is termed the deck height. Measure and record front and rear main
journals of crankshaft. To compute this distance, install crankshaft
and retain with center main bearing and cap only. Measure distance
from the crankshaft journal to the block deck, parallel to the
cylinder centerline.
Add one half of the main bearing journal diameter to distance
from crankshaft journal to block deck. This dimension should be
checked at front and rear of cylinder block. Both readings should be
the same.
If difference exceeds specifications, cylinder block must be
repaired or replaced. Deck height and warpage should be corrected at
the same time.
MAIN BEARING BORE & ALIGNMENT
For checking main bearing bore, remove all bearings from
cylinder block and main bearing caps. Install main bearing caps in
original location. Tighten bolts to specification. Using inside
micrometer, measure main bearing bore in 2 areas 90 degrees apart.
Determine bore size and out-of-round. If diameter is not within
specification, block must be align-bored.
For checking alignment, place a straightedge along centerline
of main bearing saddles. Check for clearance between straightedge and
main bearing saddles. Block must be align-bored if clearance is
present.
EXPANSION PLUG REMOVAL & INSTALLATION
Removal
Drill a hole in the center of expansion plug. Remove with
screwdriver or punch. Use care not to damage sealing surface.
Installation
Ensure sealing surface is free of burrs. Coat expansion plug
with sealer. Use a wooden dowel or pipe of slightly smaller diameter,
install expansion plug. Ensure expansion plug is evenly located.
OIL GALLERY PLUG REMOVAL & INSTALLATION
Removal
Remove threaded oil gallery plugs using the appropriate
wrench. Soft, press-in plugs are removed by drilling into plug and
installing a sheet metal screw. Remove plug with slide hammer or
pliers.
Installation
Ensure threads or sealing surface is clean. Coat threaded oil
gallery plugs with sealer and install. Replacement soft press-in plugs
are driven in place with a hammer and drift.
CAMSHAFT
* PLEASE READ THIS FIRST *

Fig. 31: Measuring Rotor Clearance - Typical
This Graphic For General Information Only
Install rotors in pump body. Position straightedge across
pump body. Using feeler gauge, measure clearance between rotors and
straightedge. Pump cover wear is measured using a straightedge and
feeler gauge. Replace pump if clearance exceeds specification.
GEAR TYPE
Oil pump gears must be marked for location prior to removal.
See Fig. 32 . Remove gears from pump body. Inspect gears for pitting
or damage. Inspect cover for grooving or wear.
Fig. 32: Typical Gear Type Oil Pump
This Graphic For General Information Only
Measure gear diameter and length. Measure gear housing cavity
depth and diameter. See Fig. 33. Replace components if worn or

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FU EL IN JE C TIO N S YSTE M - T B I

1 988 J e ep C hero ke e
1988 Electronic Fuel Injection
JEEP/RENIX THROTTLE BODY INJECTION
2.5L Cherokee, Comanche, Wagoneer, Wrangler
DESCRIPTION
The Throttle Body Injection (TBI) system is a single
injector system that introduces fuel into throttle body from above
throttle plate. Fuel injector, located within throttle body, is
controlled by the Electronic Control Unit (ECU).
The ECU is a sealed microprocessor that receives input
signals from several sensors and other related engine components.
Based on these inputs, ECU generates output signals that control and
adjust air/fuel mixture and ignition timing as necessary for proper
engine performance.
ECU also controls engine idle speed, emission control
systems, upshift indicator light (manual transmission only), and A/C
compressor clutch.
OPERATION
ELECTRONIC CONTROL UNIT (ECU)
On Cherokee, Comanche and Wagoneer, ECU is located under
instrument panel, above accelerator pedal. On Wrangler, ECU is
located behind glove box. Input information from various engine
sensors to ECU is used to determine engine operating conditions and
needs. Battery voltage input is used to ensure that correct output
voltage is supplied by ECU during fluctuations in battery voltage.
FUEL INJECTOR
Fuel injector is mounted in throttle body so that fuel is
injected into incoming airflow. When injector solenoid is energized,
armature and plunger move upward against spring. Check ball above
injector nozzle moves off seat and opens small orifice at end of
injector.
Fuel supplied to injector is forced around ball and through
orifice, resulting in fine spray of fuel. Volume of fuel injected is
dependent only on length of time that injector is energized by ECU,
as fuel pressure is constant at injector. During cold engine starts,
extra fuel is supplied so richer mixture will aid in starting.
FUEL PRESSURE REGULATOR
Fuel pressure regulator is integral part of throttle body.
Pressure regulator has a spring chamber that is vented to same
pressure as tip of injector. Because differential pressure between
injector nozzle and spring chamber is same, only the length of time
that injector is energized controls volume of fuel injected.
Fuel pump delivers more fuel than is required by engine.
Excess fuel goes to fuel tank from pressure regulator via fuel return
hose. Fuel pressure regulator function is mechanical and ECU does not
control it.
FUEL PUMP

METR IC C O NVER SIO NS

1988 J e ep C hero ke e
GENERAL INFORMATION
METRIC CONVERSIONS
METRIC CONVERSIONS
Metric conversions are making life more difficult for the
mechanic. In addition to doubling the number of tools required,
metric-dimensioned nuts and bolts are used alongside English
components in many new vehicles. The mechanic has to decide which tool
to use, slowing down the job. The tool problem can be solved by trial
and error, but some metric conversions aren't so simple. Converting
temperature, lengths or volumes requires a calculator and conversion
charts, or else a very nimble mind. Conversion charts are only part of
the answer though, because they don't help you "think" metric, or
"visualize" what you are converting. The following examples are
intended to help you "see" metric sizes:
LENGTH
Meters are the standard unit of length in the metric system.
The smaller units are 10ths (decimeter), 100ths (centimeter), and
1000ths (millimeter) of a meter. These common examples might help you
to visualize the metric units:
* A meter is slightly longer than a yard (about 40 inches).
* An aspirin tablet is about one centimeter across (.4 inches).
* A millimeter is about the thickness of a dime.
VOLUME
Cubic meters and centimeters are used to measure volume, just
as we normally think of cubic feet and inches. Liquid volume
measurements include the liter and milliliter, like the English quarts
or ounces.
* One teaspoon is about 4 cubic centimeters.
* A liter is about one quart.
* A liter is about 61 cubic inches.
WEIGHT
The metric weight system is based on the gram, with the most
common unit being the kilogram (1000 grams). Our comparable units are
ounces and pounds:
* A kilogram is about 2.2 pounds.
* An ounce is about 28 grams.
TORQUE
Torque is somewhat complicated. The term describes the amount
of effort exerted to turn something. A chosen unit of weight or force
is applied to a lever of standard length. The resulting leverage is
called torque. In our standard system, we use the weight of one pound
applied to a lever a foot long, resulting in the unit called a foot-
pound. A smaller unit is the inch-pound (the lever is one inch long).
Metric units include the meter kilogram (lever one meter long
with a kilogram of weight applied) and the Newton-meter (lever one

meter long with force of one Newton applied). Some conversions are:
* A meter kilogram is about 7.2 foot pounds.
* A foot pound is about 1.4 Newton-meters.
* A centimeter kilogram (cmkg) is equal to .9 inch pounds.
PRESSURE
Pressure is another complicated measurement. Pressure is
described as a force or weight applied to a given area. Our common
unit is pounds per square inch. Metric units can be expressed in
several ways. One is the kilogram per square centimeter (kg/cm
).
Another unit of pressure is the Pascal (force of one Newton on an area
of one square meter), which equals about 4 ounces on a square yard.
Since this is a very small amount of pressure, we usually see the
kiloPascal, or kPa (1000 Pascals). Another common automotive term for
pressure is the bar (used by German manufacturers), which equals 10
Pascals. Thoroughly confused? Try the examples below:
* Atmospheric pressure at sea level is about 14.7 psi.
* Atmospheric pressure at sea level is about 1 bar.
* Atmospheric pressure at sea level is about 1 kg/cm
.
* One pound per square inch is about 7 kPa.
CONVERSION FACTORS
CONVERSION FACTORS
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LENGTH
  

Millimeters (mm) Inches  .03937 

Inches Millimeters  25.4 

Meters (M) Feet  3.28084 

Feet Meters  .3048 

Kilometers(Km) Miles  .62137 
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AREA
  

Square Centimeters (cm) Square Inches  .155 

Square Inches Square Centimeters  6.45159 
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VOLUME
  

Cubic Centimeters Cubic Inches  .06103 

Cubic Inches Cubic Centimeters  16.38703 

Liters Cubic Inches  61.025 

Cubic Inches Liters  .01639 

Liters Quarts  1.05672 

Quarts Liters  .94633 

Liters Pints  2.11344 

Pints Liters  .47317 

Liters Ounces  33.81497 

Ounces Liters  .02957 
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WEIGHT
  

Grams Ounces  .03527 

Ounces Grams  28.34953 

Kilograms Pounds  2.20462 

Pounds Kilograms  .45359 
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WORK
  

Centimeter Kilograms Inch Pounds  .8676 

Pounds/Sq. Inch Kilograms/Sq.Centimeter .07031 

Bar Pounds/Sq. Inch  14.504 

\003
PR E-A LIG NM EN T C HEC KS

1988 J e ep C hero ke e
Wheel Alignment
PRE-ALIGNMENT INSPECTION PROCEDURES
PRE-ALIGNMENT CHECKS
Before making wheel alignment adjustment, perform the
following checks:
1) Tires should be equal in size and runout must not be
excessive. Tires and wheels should be in balance, and inflated to
manufacturer's specifications.
2) Wheel bearings must be properly adjusted. Steering linkage
and suspension must not have excessive looseness. Check for wear in
tie rod ends and ball joints.
3) Steering gear box must not have excessive play. Check and
adjust to manufacturer's specifications.
4) Vehicle must be at curb height with full fuel load and
spare tire in vehicle. No extra load should be on vehicle.
5) Vehicle must be level with floor and with suspension
settled. Jounce front and rear of vehicle several times and allow it
to settle to normal curb height.
6) If steering wheel is not centered with front wheels in
straight-ahead position, correct by shortening one tie rod adjusting
sleeve and lengthening opposite sleeve equal amounts.
7) Ensure wheel lug nuts are tightened to torque
specifications.