fuel cap JEEP CHEROKEE 1988 Service Repair Manual

Removal
1) Drain cooling system. Remove radiator. Discharge A/C
system if necessary. Remove A/C condenser and receiver assembly (if
equipped). Remove fuel pump (if equipped with mechanical pump),
ignition wires and distributor.
2) Remove cylinder head. See CYLINDER HEAD in this article.
Remove hydraulic lifters. Using Lifter Remover/Installer (J-21884),
remove lifters. Mark lifter location for reassembly reference.
3) Remove engine front cover. See ENGINE FRONT COVER in this
article. Remove timing chain and sprockets. Remove front bumper and
grille (if necessary). Carefully remove camshaft.
Inspection
Inspect camshaft for flaking, lobe wear or worn bearing
journals. Replace if not within specification. See ENGINE
SPECIFICATIONS tables.
Installation
Lubricate camshaft and install into place. Use care not to
damage camshaft bearings. Reverse removal procedure to complete
installation. Tighten bolts to specification.
Camshaft Bearing
Replace camshaft bearings using camshaft bearing
remover/installer. Ensure oil holes are aligned after installation.
OIL PAN
See OIL PAN REMOVAL at end of ENGINE section.
PISTON & ROD
NOTE: Mark piston cylinder location for reassembly reference.
Install pistons in original cylinder location.
Removal
1) Remove cylinder head. See CYLINDER HEAD in this article.
Remove oil pan. See OIL PAN REMOVAL at end of ENGINE section. Remove
ridge or deposits from cylinder bore.
2) Mark connecting rod and piston for cylinder
identification. Remove bearing cap. Remove piston and rod assembly.
CAUTION: Arrows on top of piston must point toward front of engine.
Oil squirt holes in connecting rod must face camshaft side
of engine.
Installation
1) Ensure ring end gap and side clearance are within
specification. See ENGINE SPECIFICATIONS tables. Install rings on
piston. Position ring end gaps at specified areas. See Fig. 5. Ring
gaps may vary 20 degrees from positions illustrated.

TORQUE SPECIFICATIONS TABLE








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Application Ft. Lbs. (N.m)
Camshaft Sprocket Bolt .......................... 80 (109)
Connecting Rod Cap Nut ........................... 33 (45)
Crankshaft Pulley-to-Damper Bolt ................. 20 (27)
Cylinder Head Bolt
4.0L
No. 11 .................................... 100 (135)
All Others ................................. 110 (149)
4.2L
No. 11 ..................................... 75 (102)
All Others .................................. 85 (115)
Exhaust Pipe-to-Manifold Bolt .................... 20 (27)
Fan & Hub Bolt ................................... 18 (24)
Flywheel-to-Crankshaft Bolt .................... 105 (142)
Fuel Rail Bolt ................................... 20 (27)
Intake & Exhaust Manifold Bolt
4.0L
Exhaust Manifold Bolts 1-5 ................... 23 (31)
Exhaust Manifold Bolts 6-7 .................. 17 (23)
Exhaust Manifold Bolts 8-11 ................. 23 (31)
Exhaust Manifold Bolts 12-13 ................ 30 (41)
4.2L ........................................... 23 (31)
Main Bearing Cap Bolt
Step 1 ......................................... 40 (54)
Step 2 ......................................... 70 (95)
Step 3 ........................................ 80 (109)
Oil Pump Attaching Bolt
Short .......................................... 10 (14)
Long ........................................... 17 (23)
Oxygen Sensor .................................... 35 (47)
Rocker Arm Bolt .................................. 19 (26)
Vibration Damper Bolt ....................... (1) 80 (109)
Water Pump Bolts ................................. 13 (18)
INCH Lbs. (N.m)
Engine Front Cover
Bolt ............................................ 60 (7)
Studs ......................................... 192 (22)
Oil Pan Bolt
1/4" X 20 ....................................... 84 (9)
5/16" X 18 .................................... 132 (15)
Oil Pump Cover Bolt ............................... 70 (8)
Valve Cover Bolt .................................. 55 (5)
( 1) - Clean and lubricate with oil prior to tightening.









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ENGINE SPECIFICATIONS
GENERAL ENGINE SPECIFICATIONS
GENERAL SPECIFICATIONS TABLE








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Application In. (mm)
4.0L
Displacement

These small voltage spikes give the ECU information for calculating
engine speed.
When a large tooth and notch pass the magnetic core of the
sensor, the concentration and collapse of the magnetic field created
induces a higher voltage spike into the sensor pick-up coil windings.
This higher voltage spike indicates to the ECU that a piston will soon
be at TDC (12 teeth later).
The ECU uses speed sensor information for advancing or
retarding ignition timing, dependent upon input from other sensors and
switches.
A/C "ON" Switch
This switch signals the ECU that the A/C system is energized.
This signal is used by the ECU to increase idle speed.
Starter Motor Relay
Although no switch or sensor is used, the ECU requires this
information for fuel enrichment during starting. This information is
passed on the the ECU through the starter motor relay.
Distributor Reference Signal
Although no switch or sensor is used, the ECU requires this
information for ignition timing and fuel supply. This information is
relayed to the ECU through a "synch pulse" provided by the distributor
stator. This allows the ECU to synchronize injector opening with
intake valve opening.
ELECTRONIC CONTROL MODULE (ECM)
The Electronic Control Unit (ECU) is the "brain" of the
engine control system. The ECU is located in the passenger
compartment, under left side of dash to right of steering column.
The ECU senses engine operating conditions, processes input
signals, and controls the various systems that affect vehicle
performance.
DIAGNOSTICS
The engine control system has diagnostic capabilities. Using
System Tester (M.S. 1700), diagnostics can be performed on the system
to more accurately determine faulty components. The diagnostic
connectors are located in the engine compartment at the right shock
tower (or under left side of instrument panel).
NOTE: Information for diagnosing the engine control system using
the System Tester (M.S. 1700) was not available from
manufacturer. Only component testing is provided.
ELECTRONIC SPARK ADVANCE
Based upon engine operating conditions received from the
sensors and switches, the ECU controls spark timing. The ECU triggers
the ignition coil through the ignition control module.
IDLE SPEED CONTROL
Idle speed is controlled by the ECU through the idle speed
stepper motor. A latch relay is used to program the stepper motor for
engine start-up. The relay is located on the right inner fender panel.
See Fig. 1 . The ECU energizes the latch relay when engine is in
cranking mode, and keeps the relay energized for 3-5 seconds after the
engine is stopped. In this way, the stepper motor can provide the

proper increased enrichment for the next engine start. Idle speed is
nonadjustable.
EMISSION CONTROL
The ECU electrically controls Exhaust Gas Recirculation (EGR).\
An ECU-controlled solenoid valve is used to control EGR valve
function. This valve is located on the left inner fender panel and is
operated by the ECU in response to coolant temperature, throttle
position, and manifold pressure.
Under conditions of engine warm-up, engine idle, wide open
throttle, or rapid acceleration/deceleration, the solenoid valve is
energized, blocking vacuum to the EGR valve. At normal operating
temperatures with engine speed above idle, the solenoid valve is de-
energized, allowing normal EGR valve function.
NOTE: If the electrical connector is removed from the EGR solenoid,
EGR flow will be allowed at all times.
A/C CLUTCH CONTROL
The ECU controls the A/C compressor clutch to improve idle
quality. The A/C compressor clutch will be engaged or disengaged as
deemed necessary by the ECU through the A/C clutch relay.
SHIFT LIGHT CONTROL
The shift light system is used on all manual transmission
equipped vehicles. The ECU monitors coolant temperature, throttle
position, vehicle speed, and engine speed to control the shift light.
The ECU calculates what gear position the vehicle should be in and
uses this information to turn on the light. The light indicates the
best shift point to the driver for maximum fuel economy.
The light is tested when the ignition switch is turned on.
When the engine is started, the light should go out. A transmission-
mounted switch prevents the light from illuminating when the
transmission is shifted into high gear. The ECU turns the light off if
the shift to the next higher gear is not performed within 3-5 seconds
after light comes on.
DIAGNOSIS & TESTING
PRELIMINARY CHECKS
Before assuming that the ECU is faulty, the following systems
and components must be in good condition and operating properly:
* Air filter.
* All support systems and wiring.
* Battery connections and specific gravity.
* Compression pressure.
* Electrical and vacuum connections to components, sensors and
switches.
* Emission control devices.
* Ignition system.
* All vacuum and fuel line (hose) connections.
FUEL SYSTEM TEST
Fuel Pressure
1) Remove cap from pressure test port on fuel rail and

connect Fuel Pressure Gauge (J-34730-1). See Fig. 3. Start engine and
observe fuel pressure. With vacuum hose connected to pressure
regulator, pressure should be about 31 psi (2.2 kg/cm
)), and about 39
psi (2.7 kg/cm)) with vacuum hose disconnected.
2) If pressure is not as specified, inspect fuel supply and
return lines for kinks and obstructions. If fuel lines are okay,
replace pressure regulator. Remove gauge and install cap on test port.
Fuel Flow
1) Remove cap from the pressure test port on the fuel rail.
See Fig. 3 . Connect piece of hose to port and place other end in
graduated container of at least one quart (1L) capacity.
2) Pinch off fuel return line. Run fuel pump by placing
jumper wire between terminals "D1-5" and "D1-6" of diagnostic
connector "D1". If fuel flow is less than one quart (1L) in one
minute, replace fuel pump. Remove hose and install test port plug.
Fig. 3: Location of Fuel Pressure Test Port
Fuel Injector Test
See the FUEL INJECTOR DIAGNOSTICS chart near the end of this
article. See Fig. 9









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ABBREVIATION DEFINITION 










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B/P Backpressure 

BAC By-Pass Air Control 

BAP Barometric Absolute Pressure Sensor 

BARO Barometric 

BBDC Before Bottom Dead Center 

BCM Body Control Module 

BDC Bottom Dead Center 

BHP Brake Horsepower 

BLK Black 

BLU Blue 

BMAP Barometric & Manifold Absolute Pressure Sensor 

BOO Brake On-Off Switch 

BP Barometric Pressure sensor 

BPS Barometric Pressure Sensor 

BPT Backpressure Transducer 

BRN Brown 

BTDC Before Top Dead Center 

BTU British Thermal Unit 

BVSV Bimetallic Vacuum Switching Valve 

Baro. Barometric 

Batt. Battery 

Bbl. Barrel (Example: 4-Bbl.) 

Blst. Ballast 

Blwr. Blower 

Brkr. Breaker 











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"C" ABBREVIATION TABLE
"C" ABBREVIATION TABLE







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ABBREVIATION DEFINITION 










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C Celsius (Degrees) 

C(3) I Computer Controlled Coil Ignition 

C(4) Computer Controlled Catalytic Converter 

CANP Canister Purge solenoid 

CARB California Air Resources Board 

CAT Catalytic Converter 

CB Circuit Breaker 

CBD Closed Bowl Distributor 

CBVV Carburetor Bowl Vent Valve 

cc Cubic Centimeter 

CCC Computer Command Control 

CCD Computer Controlled Dwell 

CCM Central Control Module 

CCO Converter Clutch Override 

CCOT Cycling Clutch Orifice Tube 

CCW Counterclockwise 

CDI Capacitor Discharge Ignition 

CEC Computerized Engine Control 

CFI Central Fuel Injection 

CID Cubic Inch Displacement 

CID Cylinder Identification sensor 

CIS Continuous Injection System 

CIS-E Continuous Injection System-Electronic 

CKT Circuit 

CLR Clear 

CNG Compressed Natural Gas 

AIR IN JE C TIO N S YSTE M

1988 J e ep C hero ke e
1988 Exhaust Emission Systems
JEEP PULSE AIR INJECTION SYSTEM
4.2L
DESCRIPTION
Pulse air injection system is used to inject fresh air into
exhaust system. When fresh air is injected into hot exhaust gases,
combustion takes place. This reduces amount of unburned fuel that
escapes into the atmosphere.
System consists of check valves, control valves, control
valve solenoids, vacuum reservoir, vacuum lines and air lines. Pulse
air system is capable of injecting air at both catalytic converter
(downstream) or at front exhaust pipe.
OPERATION
Pulse air system uses alternating positive and negative
pressure pulsations in exhaust system to draw in fresh air through
air cleaner. Check valves are used to allow fresh air into exhaust,
but prevent exhaust from flowing back into intake system.
Air is switched between upstream and downstream injection by
2 vacuum-operated control valves. Each control valve is switched by
an electrically operated-vacuum solenoid.
Vacuum solenoids are switched on and off by MCU according to
engine operating conditions. Vacuum storage tank maintains vacuum
supply to switching solenoids.
DIAGNOSIS & TESTING
1) Check condition of all hoses and lines in system. Reroute
any kinked or restricted hoses. Repair or replace any cracked or
broken hoses. To check system operation, feel for suction in
injection hoses at air cleaner.
2) If problem exists, check to see if vacuum is being
supplied to the valve. If vacuum is not present at valve(s), check
vacuum lines or ports.

Fig. 3: Typical Thermostatic Air Cleaner System
FUEL EVAPORATIVE SYSTEM (EVAP)
The EVAP system allows for proper fuel system ventilation
while preventing fuel vapors from reaching the atmosphere. This means
that vapors must be caught and stored while the engine is off, which
is when most fuel evaporation occurs. When the engine is started,
these fuel vapors can be removed from storage and burned. In most
systems, storage is provided by an activated charcoal (or carbon)
canister. See Fig. 4. On a few early systems, charcoal canisters are
not used. Instead, fuel vapors are vented into the PCV system and
stored inside the crankcase.
The main components of a fuel evaporation system are a sealed
fuel tank, a liquid-vapor separator and vent lines to a vapor-storing
canister filled with activated charcoal. The filler cap is normally
not vented to the atmosphere, but is fitted with a valve to allow both
pressure and vacuum relief.
Although a few variations do exist between manufacturers,
basic operation is the same for all systems. Check for presence of
vapor storage canister or crankcase storage connections when required.
Ensure required hoses, solenoids, etc., are present and connected
properly. Check for proper type fuel tank cap. Check for any non-OEM
or auxiliary fuel tanks for compliance and the required number of
evaporation canisters.

\003
EN G IN E R EM OVA L - 4 -C YL

1988 J e ep C hero ke e
1988 ENGINES
Jeep - Engine Removal - 4-Cylinder
Cherokee, Comanche, Wrangler
4-CYLINDER ENGINES
2.5L
1) Disconnect negative battery cable. Drain cooling system.
Remove air cleaner, lower radiator hose, fan shroud, and engine
compartment light from hood. Scribe hinge locations and remove hood.
Disconnect automatic transmission cooler lines at radiator (if
equipped).
2) Remove upper radiator hose, fan assembly and coolant
recovery hose. Remove radiator and A/C condenser (if equipped). Hold
fan pulley to water pump flange using 5/16" x 1/2" SAE capscrew.
Disconnect heater hoses, throttle linkages, cruise control cable (if
equipped) and Throttle valve rod.
3) Disconnect wires from starter and separate CEC system
wiring harness connector. Disconnect fuel pipe from fuel pump and fuel
return hose from fuel filter. Disconnect hoses from A/C compressor and
power steering pump (if equipped). Drain power steering pump
reservoir. Cap all fittings and hose ends.
4) Remove vacuum check valve from brake booster (if
equipped). Tag and remove all wiring and vacuum lines connected to
engine or accessories. Raise vehicle and remove starter. Disconnect
exhaust pipe from manifold.
5) Remove converter/flywheel housing cover. Remove engine
mount nuts at bracket side. On automatic transmission models, index
mark drive plate and torque converter. Remove drive plate-to-converter
bolts.
6) Remove upper and loosen lower bellhousing-to-engine bolts.
Attach lifting equipment to engine. Raise engine off front mounts,
Place support under bellhousing. Remove remaining bellhousing-to-
engine bolts. Lift engine out of engine compartment.
NOTE: Engine mount pads may be removed from engine brackets to
align engine and transmission during installation.
TORQUE SPECIFICATIONS
TORQUE SPECIFICATIONS TABLE








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Application Ft. Lbs. (N.m)
Clutch Housing-to-Block Bolts .................... 55 (75)
Drive Plate-to-Converter ......................... 26 (35)
Flywheel Bolts ............................... ( 1) 50 (68)
Front Support Bracket-to-Block ................... 45 (61)
Front Support Cushion-to-Crossmember ............. 33 (45)
Rear Support Bracket-to-Transmission ............. 33 (45)
Rear Support Cushion-to-Bracket .................. 30 (41)
Starter Motor-to-Block ........................... 33 (45)
( 1) - Tighten an additional 60 degrees.









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\003
EN G IN E R EM OVA L - 6 -C YL

1988 J e ep C hero ke e
1988 ENGINES
Jeep - Engine Removal - 6-Cylinder
Cherokee, Comanche, Wagoneer, Wrangler
6-CYLINDER ENGINES
4.0L
1) Scribe hinge locations, remove engine compartment light
(if equipped) and remove hood. Disconnect battery cables and remove
battery. Drain cooling system.
2) Disconnect wire connectors from alternator, ignition coil
and distributor. Disconnect oil pressure sender wire, starter wires
and fuel injector wiring harness (if equipped). Detach 2 fuel pipe
quick connect couplings at left inner fender panel. Disconnect engine
ground strap and remove air cleaner.
3) Disconnect the vacuum purge hose at fuel vapor canister
tee. Disconnect wire from idle speed actuator and oxygen sensor.
Detach throttle cable from bracket and disconnect throttle valve rod
at bellcrank. Remove upper and lower radiator hoses.
4) On automatic transmission models, disconnect the
transmission fluid cooler tubing. On all models, remove fan shroud and
radiator. Remove fan and spacer or Tempatrol fan assembly. Hold fan
pulley to water pump flange using 5/16" x 1/2" SAE capscrew while
crankshaft is rotated.
5) Disconnect cruise control cable (if equipped). Disconnect\
wires from starter motor solenoid and disconnect CEC system harness.
Remove power brake vacuum check valve from booster (if equipped).
6) Disconnect power steering hoses from steering gear (if
equipped). Drain power steering pump reservoir and plug end of hoses.
Cap all fittings on steering gear and hoses. Raise and support
vehicle. Remove starter. Remove flywheel housing access cover.
7) Remove upper and loosen lower bellhousing-to-engine bolts.
Attach lifting equipment to engine. Raise engine off front mounts.
Place support under bellhousing. Remove remaining bellhousing-to-
engine bolts. Lift engine out of engine compartment.
4.2L
1) Remove battery and drain cooling system. Remove air
cleaner and engine compartment light from hood. Scribe hinge location
and remove hood. Disconnect and plug front fuel line at pump and fuel
return line at frame.
2) Disconnect heater hoses at heater. Label and disconnect
all wiring, lines, linkage and hoses at engine. Remove vacuum switch
assembly bracket from cylinder head cover. Remove both radiator hoses
and automatic transmission oil lines (if equipped) at radiator. Remove\
radiator and shroud.
3) Remove fan and spacer. Use 5/16" x 1/2" SAE bolt to hold
fan pulley to water pump flange. Remove starter and disconnect engine
ground strap. Remove engine mount-to-bracket nuts. Disconnect exhaust
pipe at manifold.
4) Discharge A/C system (if equipped). Disconnect and plug
hose or port openings at compressor. Disconnect hoses at power
steering gear and drain reservoir. Remove power brake vacuum check
valve. Remove bracket bolt for automatic transmission filler tube (if
equipped).
5) Lift and support vehicle. On models with automatic