1988 JEEP CHEROKEE oil pressure

ENGINES








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High Oil Improper grade of oil Replace with proper oil
Pressure Oil pressure relief valve Eliminate binding
stuck closed
Oil pressure sender or Replace sender or gauge
gauge faulty









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Noisy Main Inadequate oil supply Check oil delivery to
Bearings main bearings
Excessive main bearing Replace main bearings,
clearance See ENGINES
Excessive crankshaft end Replace crankshaft, See
play ENGINES
Loose flywheel or torque Tighten attaching bolts
converter
Loose or damaged vibration Tighten or replace
damper vibration damper
Crankshaft journals Re-grind crankshaft
out-of-round journals
Excessive belt tension Loosen belt tension









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Noisy Connecting Excessive bearing clearance Replace bearing, See
Rods or missing bearing ENGINES
Crankshaft rod journal Re-grind crankshaft
out-of-round journal
Misaligned connecting rod Remove rod or cap and
or cap realign
Incorrectly tightened rod Remove and re-tighten
bolts rod bolts









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Noisy Pistons Excessive piston-to-bore Install larger pistons,
and Rings clearance See ENGINES
Bore tapered or out-of-round Rebore block
Piston ring broken Replace piston rings,
See ENGINES
Piston pin loose or seized Replace piston pin, See
ENGINES
Connecting rods misaligned Realign connecting rods
Ring side clearance too Replace with larger or
loose or tight smaller rings
Carbon build-up on piston Remove carbon









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Noisy Valve Worn or bent push rods Replace push rods, See
Train ENGINES
Worn rocker arms or bridged Replace push rods, See
pivots ENGINES
Dirt or chips in valve Remove lifters and
lifters remove dirt/chips
Excessive valve lifter Replace valve lifters,
leak-down See ENGINES
Valve lifter face worn Replace valve lifters,
See ENGINES
Broken or cocked valve replace or reposition
springs springs
Too much valve stem-to-guide Replace valve guides,
clearance See ENGINES
Valve bent Replace valve, See
ENGINES
Loose rocker arms Retighten rocker arms,
See ENGINES
Excessive valve seat Reface valve seats, See
run-out ENGINES

Incorrect injector pump Check pressure, see
housing pressure FUEL SYSTEMS









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Engine Cooling system leaks Check cooling system
Overheating and repair leaks
Belt slipping or damaged Check tension and/or
replace belt
Thermostat stuck closed Remove and replace
thermostat, see
ENGINE COOLING
Head gasket leaking Replace head gasket









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Oil Light on at Low oil pump pressure Check oil pump
Idle operation, see ENGINES
Oil cooler or line Remove restriction
restricted and/or replace cooler









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Engine Won't Injector pump fuel solenoid Remove and check
Shut Off does not return fuel valve solenoid and replace
to OFF position if needed









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VACUUM PUMP DIAGNOSIS
Excessive Noise Loose pump-to-drive Tighten screws
assembly screws
Loose tube on pump assembly Tighten tube
Valves not functioning Replace valves
properly
Oil Leakage Loose end plug Tighten end plug
Bad seal crimp Remove and re-crimp
seal









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FUEL INJECTION TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
BASIC FUEL INJECTION TROUBLE SHOOTING CHART









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CONDITION POSSIBLE CAUSE CORRECTION








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Engine Won't Cold start valve inoperative Test valve and
Start (Cranks circuit
Normally)
Poor connection;vacuum or Check vacuum and
wiring electrical
connections
Contaminated fuel Test fuel for water
or alcohol
Defective fuel pump relay Test relay and
or circuit wiring
Battery too low Charge and test
battery

Low fuel pressure Test pressure regul-
ator and fuel pump,
check for restricted
lines and filters
No distributor reference Repair ignition
pulses system as necessary
Open coolant temperature Test sensor and
sensor circuit wiring
Shorted W.O.T. switch in Disconnect W.O.T.
T.P.S. switch, engine
should start
Defective ECM Replace ECM
Fuel tank residual pressure Test for fuel
valve leaks pressure drop after
shut down









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Hard Starting Disconnected hot air tube Reconnect tube and
to air cleaner test control valve
Defective Idle Air Control Test valve operation
(IAC) valve and circuit
Shorted, open or misadjusted Test and adjust or
T.P.S. replace T.P.S.
EGR valve open Test EGR valve and
control circuit
Poor Oxygen sensor signal Test for shorted or
circuit
Incorrect mixture from PCV Test PCV for flow,
system check sealing of oil
filter cap









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Poor High Speed Low fuel pump volume Faulty pump or
Operation restricted fuel
lines or filters
Poor MAP sensor signal Test MAP sensor,
vacuum hose and
wiring
Poor Oxygen sensor signal Test for shorted or
open sensor or
circuit
Open coolant temperature Test sensor and
sensor circuit wiring
Faulty ignition operation Check wires for
cracks or poor con-
nections, test
secondary voltage
with oscilloscope
Contaminated fuel Test fuel for water

or alcohol
Intermittent ECM ground Test ECM ground
connection for
resistance
Restricted air cleaner Replace air cleaner
Restricted exhaust system Test for exhaust
manifold back
pressure
Poor MAF sensor signal Check leakage
between sensor and
manifold
Poor VSS signal If tester for ALCL
hook-up is available
check that VSS
reading matches
speedometer









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Ping or Knock on Poor Knock sensor signal Test for shorted or
Acceleration open sensor or
circuit
Poor Baro sensor signal Test for shorted or
open sensor or
circuit
Improper ignition timing See VEHICLE EMISSION
CONTROL LABEL (where
applicable)
Check for engine Low coolant, loose
overheating problems belts or electric
cooling fan
inoperative









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NOTE: For additional electronic fuel injection trouble shooting
information, see the appropriate article in the ENGINE
PERFORMANCE section (not all vehicles have Computer Engine
Control articles). Information is provided there for
diagnosing fuel system problems on vehicles with electronic
fuel injection.
IGNITION SYSTEM TROUBLE SHOOTING
NOTE: This is GENERAL information. This article is not intended
to be specific to any unique situation or individual vehicle
configuration. The purpose of this Trouble Shooting
information is to provide a list of common causes to
problem symptoms. For model-specific Trouble Shooting,
refer to SUBJECT, DIAGNOSTIC, or TESTING articles available
in the section(s) you are accessing.
Ignition Secondary Trouble Shooting Chart








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START: Visually inspect Spark Plug Wires, Coil Wires, 

Plug Wire Boots, Rotor, and Distributor Cap for 

signs of damage. 

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CONDITION POSSIBLE CAUSE CORRECTION








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Chattering or Incorrect clutch adjustment Adjust clutch
Grabbing
Oil, grease or glaze on Disassemble and clean
facings or replace
Loose "U" joint flange See DRIVE AXLES
article
Worn input shaft spline Replace input shaft
Binding pressure plate Replace pressure plate
Binding release lever See CLUTCH article
Binding clutch disc hub Replace clutch disc
Unequal pressure plate Replace worn/misaligned
contact components
Loose/bent clutch disc Replace clutch disc
Incorrect transmission Realign transmission
alignment
Worn pressure plate, disc Replace damaged
or flywheel components
Broken or weak pressure Replace pressure
springs plate
Sticking clutch pedal Lubricate clutch pedal
& linkage
Incorrect clutch disc Replace clutch disc
facing
Engine loose in chassis Tighten all mounting
bolts









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Failure to Oil or grease on clutch Clean or replace clutch
Release facings clutch disc
Incorrect release lever or See CLUTCH article
pedal adjustment
Worn or broken clutch Replace clutch disc
facings
Bent clutch disc or Replace damaged
pressure plate components
Clutch disc hub binding on Clean or replace clutch
input shaft disc and/or input shaft
Binding pilot bearing Replace pilot bearing
Sticking release bearing Replace release bearing
sleeve and/or sleeve
Binding clutch cable See CLUTCH article

Defective clutch master Replace master cylinder
Defective clutch slave Replace slave cylinder
Air in hydraulic system Bleed hydraulic system









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Rattling Weak or broken release Replace spring and
lever spring check alignment
Damaged pressure plate Replace pressure plate
Broken clutch return spring Replace return spring
Worn splines on clutch disc Replace clutch disc
or input shaft and/or input shaft
Worn clutch release bearing Replace release bearing
Dry or worn pilot bearing Lubricate or replace
pilot bearing
Unequal release lever Align or replace
contact release lever
Incorrect pedal free play Adjust free play
Warped or damaged clutch Replace damaged
disc components









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Slipping Pressure springs worn or Release pressure plate
Oily, greasy or worn Clean or replace clutch
facings disc
Incorrect clutch alignment Realign clutch assembly
Warped clutch disc or Replace damaged
pressure plate components
Binding release levers or Lubricate and/or
clutch pedal replace release
components









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Squeaking Worn or damaged release Replace release bearing
Dry or worn pilot or Lubricate or replace
release bearing assembly
Pilot bearing turning in Replace pilot bearing
crankshaft and/or crankshaft
Worn input shaft bearing Replace bearing and
seal
Incorrect transmission Realign transmission
alignment
Dry release fork between Lubricate release fork
pivot and pivot









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Heavy and/or Sticking release bearing Replace release bearing
Stiff Pedal sleeve and/or sleeve

Dry or binding clutch Lubricate and align
pedal hub components
Floor mat interference Lay mat flat in proper
with pedal area
Dry or binding ball/fork Lubricate and align
pivots components
Faulty clutch cable Replace clutch cable









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Noisy Clutch Faulty interlock switch Replace interlock
Pedal switch
Self-adjuster ratchet Lubricate or replace
noise self-adjuster
Speed control interlock Lubricate or replace
switch interlock switch









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Clutch Pedal Binding clutch cable See CLUTCH article
Sticks Down
Springs weak in pressure Replace pressure plate
plate
Binding in clutch linkage Lubricate and free
linkage









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Noisy Dry release bearing Lubricate or replace
release bearing
Dry or worn pilot bearing Lubricate or replace
bearing
Worn input shaft bearing Replace bearing









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Transmission Weak springs in pressure Replace pressure plate
Click plate
Release fork loose on ball Replace release fork
stud and/or ball stud
Oil on clutch disc damper Replace clutch disc
Broken spring in slave Replace slave cylinder
cylinder









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DRIVE AXLE - NOISE DIAGNOSIS
Unrelated Noises
Some driveline trouble symptoms are also common to the
engine, transmission, wheel bearings, tires, and other parts of the
vehicle. Ensure cause of trouble actually is in the drive axle before
adjusting, repairing, or replacing any of its parts.
Non-Drive Axle Noises
A few conditions can sound just like drive axle noise and
have to be considered in pre-diagnosis. The 4 most common noises are
exhaust, tires, CV/universal joints and wheel trim rings.

Reaction ring sticking See POWER STEERING GEAR
in housing head article
Steering pump internal See POWER STEERING PUMP
leakage article
Steering gear-to-column See STEERING COLUMN
misalignment article
Lack of lubrication in Service front suspension
linkage
Lack of lubrication in Service front suspension
ball joints









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Increased Effort High internal pump leakage See POWER STEERING PUMP
When Turning article
Wheel Fast Power steering pump belt Adjust or replace if
Foaming, Milky slipping necessary
Power Steering
Fluid, Low Fluid Low fluid level Check and fill to
Level or Low proper level
Pressure
Engine idle speed to low Adjust to correct
setting
Air in pump fluid system See POWER STEERING PUMP
article
Pump output low See POWER STEERING PUMP
article
Steering gear See POWER STEERING GEAR
malfunctioning article









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Wheel Surges Low fluid level Check and fill to proper
or Jerks level
Loose fan belt Adjust or replace if
necessary
Insufficient pump See POWER STEERING PUMP
pressure article
Sticky flow control valve See POWER STEERING PUMP
article
Linkage hitting oil pan Replace bent components
at full turn









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Kick Back or Air in pump fluid system See POWER STEERING PUMP
Free Play article
Worn poppet valve in See POWER STEERING PUMP
steering gear article
Excessive over center See POWER STEERING GEAR
lash article
Thrust bearing out of See POWER STEERING GEAR
adjustment article