POWER
DISTRIBUTION
CENTER
6
POWERTRAIN
CONTROL
MODULE
24FUSE40A
BATT A0
C76
A16
12
GY
NO. 1 RELAY
FAN
RADIATOR
6
RADIATOR
FAN
RELAY
NO. 2
48
2662
4
NO. 3 RELAY
FAN
RADIATOR
4
312
ES07
C25
12
YL
LOW
SPEED
RADIATOR
RELAY NO. 2
CONTROLC24
20
DB/PK
CONTROL NO.1 & NO.3RADIATORSPEEDHIGH
48
ES09
1E95
B10710B106 E97ES29
C24
20
DB/PK
C137
20
YLC137
20
YL
C137
20
YL
A142
18
DG/ORA142
18
DG/ORA142
18
DG/OR
C27
12
DB/PKC27
12
DB/PK
C27
12
DB/PK
BATT A17
ES12
G102
Z1
12
BK
Z1
12
BK
Z1
12
BK
C116
12
LG/WT
DRIVER'S
SIDE
RADIATOR
FAN FANRADIATOR
SIDE
PASSENGER'S
MMDISCONNECT
FAN
RADIATOR
48
258A17
12
RD/BK
(8W-10-8)
(8W-30-37)(8W-10-15)(8W-10-8)
(8W-10-25)
(8W-15-3)
(8W-15-3)(8W-10-19)
8W - 42 - 10 8W-42 AIR CONDITIONING-HEATER
DIESELNS/GS
J988W-3GS004210
(5) Test resistance of spark plug cables. Refer to
Group 8D, Ignition System.
(6) Test ignition coils primary and secondary resis-
tance. Replace parts as necessary. Refer to Group 8D,
Ignition System.
(7) Check fuel pump pressure at idle and different
RPM ranges. Refer to Group 14, Fuel System for
Specifications.
(8) The air filter elements should be replaced as
specified in Group 0, Lubrication and Maintenance.
(9) Inspect crankcase ventilation system as out-
lined in Group 25, Emission Control Systems.
(10) Road test vehicle as a final test.
HONING CYLINDER BORES
(1) Used carefully, the cylinder bore resizing hone
C-823 equipped with 220 grit stones, is the best tool
for this job. In addition to deglazing, it will reduce
taper and out-of-round as well as removing light
scuffing, scoring or scratches. Usually a few strokes
will clean up a bore and maintain the required lim-
its.
(2) Deglazing of the cylinder walls may be done
using a cylinder surfacing hone, Tool C-3501,
equipped with 280 grit stones, if the cylinder bore is
straight and round. 20-60 strokes depending on the
bore condition, will be sufficient to provide a satisfac-
tory surface. Inspect cylinder walls after each 20
strokes, using a light honing oil.Do not use engine
or transmission oil, mineral spirits or kerosene.
(3) Honing should be done by moving the hone up
and down fast enough to get a cross-hatch pattern.
When hone marksintersectat 50-60 degrees, the
cross hatch angle is most satisfactory for proper seat-
ing of rings (Fig. 2).(4) A controlled hone motor speed between
200-300 RPM is necessary to obtain the proper cross-
hatch angle. The number of up and down strokes per
minute can be regulated to get the desired 50-60
degree angle. Faster up and down strokes increase
the cross-hatch angle.
(5) After honing, it is necessary that the block be
cleaned again to remove all traces of abrasive.
CAUTION: Ensure all abrasives are removed from
engine parts after honing. It is recommended that a
solution of soap and hot water be used with a
brush and the parts then thoroughly dried. The bore
can be considered clean when it can be wiped
clean with a white cloth and cloth remains clean.
Oil the bores after cleaning to prevent rusting.
MEASURING MAIN BEARING AND CONNECTING
ROD BEARING CLEARANCES
PLASTIGAGE METHOD
Engine crankshaft bearing clearances can be deter-
mined by use of Plastigage or equivalent. The follow-
ing is the recommended procedure for the use of
Plastigage:
NOTE: The total clearance of the main bearings
can only be determined by removing the weight of
the crankshaft. This can be accomplished by either
of two methods:
PREFERRED METHOD
Shimming the bearings adjacent to the bearing to
be checked in order to remove the clearance between
upper bearing shell and the crankshaft. This can be
accomplished by placing a minimum of 0.254 mm
(0.010 in.) shim (e. g. cardboard, matchbook cover,
etc.) between the bearing shell and the bearing cap
on the adjacent bearings and tightening bolts to
14-20 N´m (10-15 ft. lbs.). The number of main bear-
ing will vary from engine to engine.
Fig. 2 Cylinder Bore Cross-Hatch Pattern
Fig. 3 Plastigage Placed in Lower Shell
NSENGINE 9 - 3
GENERAL INFORMATION (Continued)
ENGINE DIAGNOSIS
INDEX
page page
DIAGNOSIS AND TESTING
CYLINDER COMBUSTION
PRESSURE LEAKAGE TEST.............. 8
CYLINDER COMPRESSION PRESSURE TEST . . 7
ENGINE DIAGNOSISÐMECHANICAL......... 12
ENGINE DIAGNOSISÐPERFORMANCE...... 10GENERAL INFORMATION.................. 7
INSPECTION
(ENGINE OIL LEAKS IN GENERAL)......... 8
INTAKE MANIFOLD LEAKAGE DIAGNOSIS..... 7
LASH ADJUSTER (TAPPET)
NOISE DIAGNOSIS...................... 8
DIAGNOSIS AND TESTING
GENERAL INFORMATION
Engine diagnosis is helpful in determining the
causes of malfunctions.
These malfunctions may be classified as either
mechanical (e.g., a strange noise), or performance
(e.g., engine idles rough and stalls).
Refer to the Service DiagnosisÐMechanical Chart
and the Service DiagnosisÐPerformance Chart, for
possible causes and corrections of malfunctions. Refer
to Group 14, Fuel System, for the fuel system diag-
nosis.
Additional tests and diagnostic procedures may be
necessary for specific engine malfunctions that can-
not be isolated with the Service Diagnosis charts.
Information concerning additional tests and diagno-
sis is provided within the following:
²Cylinder Compression Pressure Test
²Cylinder Combustion Pressure Leakage Test
²Engine Cylinder Head Gasket Failure Diagnosis
²Intake Manifold Leakage Diagnosis
INTAKE MANIFOLD LEAKAGE DIAGNOSIS
An intake manifold air leak is characterized by
lower than normal manifold vacuum. Also, one or
more cylinders may not be functioning.
WARNING: USE EXTREME CAUTION WHEN THE
ENGINE IS OPERATING. DO NOT STAND IN A
DIRECT LINE WITH THE FAN. DO NOT PUT YOUR
HANDS NEAR THE PULLEYS, BELTS OR THE FAN.
DO NOT WEAR LOOSE CLOTHING.
(1) Start the engine.
(2) Spray a small stream of water (Spray Bottle) at
the suspected leak area.
(3) If a change in RPM'S, the area of the suspected
leak has been found.
(4) Repair as required.
CYLINDER COMPRESSION PRESSURE TEST
The results of a cylinder compression pressure test
can be utilized to diagnose several engine malfunc-
tions.
Ensure the battery is completely charged and the
engine starter motor is in good operating condition.
Otherwise the indicated compression pressures may
not be valid for diagnosis purposes.
(1) Check engine oil level and add oil if necessary.
(2) Drive the vehicle until engine reaches normal
operating temperature. Select a route free from traf-
fic and other forms of congestion, observe all traffic
laws, and accelerate through the gears several times
briskly.
(3) Remove all spark plugs from engine. As spark
plugs are being removed, check electrodes for abnor-
mal firing indicators fouled, hot, oily, etc. Record cyl-
inder number of spark plug for future reference.
(4) Disconnect coil wire from distributor and
secure to good ground to prevent a spark from start-
ing a fire (Conventional Ignition System). For Direct
Ignition System DIS disconnect the coil connector.
(5) Be sure throttle blade is fully open during the
compression check.
(6) Insert compression gage adaptor into the #1
spark plug hole in cylinder head. Crank engine until
maximum pressure is reached on gage. Record this
pressure as #1 cylinder pressure.
(7) Repeat the previous step for all remaining cyl-
inders.
(8) Compression should not be less than (689kPa)
100 psi and not vary more than 25 percent from cyl-
inder to cylinder.
(9) If one or more cylinders have abnormally low
compression pressures, repeat the compression test.
(10) If the same cylinder or cylinders repeat an
abnormally low reading on the second compression
test, it could indicate the existence of a problem in
the cylinder in question.The recommended com-
pression pressures are to be used only as a
guide to diagnosing engine problems. An engine
should not be disassembled to determine the
NSENGINE 9 - 7
cause of low compression unless some malfunc-
tion is present.
(11) Clean or replace spark plugs as necessary
and adjust gap as specified in Group 8, Electrical.
Tighten to specifications.
(12) Test resistance of spark plug cables. Refer to
Group 8, Electrical Ignition System Secondary Cir-
cuit Inspection.
(13) Test coil output voltage, primary and second-
ary resistance. Replace parts as necessary. Refer to
Group 8, Electrical Ignition System.
(14) Check fuel pump pressure at idle and differ-
ent RPM ranges. Refer to Group 14, Fuel System for
Specifications.
(15) The air filter elements should be replaced as
specified in Group 0, Lubrication and Maintenance,.
(16) Inspect crankcase ventilation system as out
lined in Group 0, Lubrication and Maintenance. For
emission controls see Group 25, Emission Controls
for service procedures.
(17) Inspect and adjust accessory belt drives refer-
ring to Group 7, Cooling System, Accessory Drive
Belts for proper adjustments.
(18) Road test vehicle as a final test.
CYLINDER COMBUSTION PRESSURE LEAKAGE
TEST
The combustion pressure leakage test provides an
accurate means for determining engine condition.
Combustion pressure leakage testing will detect:
²Exhaust and intake valve leaks (improper seat-
ing).
²Leaks between adjacent cylinders or into water
jacket.
²Any causes for combustion/compression pressure
loss.
WARNING: DO NOT REMOVE THE RADIATOR CAP
WITH THE SYSTEM HOT AND UNDER PRESSURE
BECAUSE SERIOUS BURNS FROM COOLANT CAN
OCCUR.
Check the coolant level and fill as required. DO
NOT install the radiator cap.
Start and operate the engine until it attains nor-
mal operating temperature, then turn the engine
OFF.
Clean spark plug recesses with compressed air.
Remove the spark plugs.
Remove the oil filler cap.
Remove the air cleaner.
Calibrate the tester according to the manufactur-
er's instructions. The shop air source for testing
should maintain 483 kPa (70 psi) minimum, 1 379
kPa (200 psi) maximum and 552 kPa (80 psi) recom-
mended.Perform the test procedures on each cylinder
according to the tester manufacturer's instructions.
While testing, listen for pressurized air escaping
through the throttle body, tailpipe and oil filler cap
opening. Check for bubbles in the radiator coolant.
All gauge pressure indications should be equal,
with no more than 25% leakage.
FOR EXAMPLE:At 552 kPa (80 psi) input pres-
sure, a minimum of 414 kPa (60 psi) should be main-
tained in the cylinder.
LASH ADJUSTER (TAPPET) NOISE DIAGNOSIS
A tappet-like noise may be produced from several
items. Check the following items.
(1) Engine oil level too high or too low. This may
cause aerated oil to enter the adjusters and cause
them to be spongy.
(2) Insufficient running time after rebuilding cylin-
der head. Low speed running up to 1 hour may be
required.
(3) During this time, turn engine off and let set for
a few minutes before restarting. Repeat this several
times after engine has reached normal operating
temperature.
(4) Low oil pressure.
(5) The oil restrictor pressed into the vertical oil
passage to the cylinder head is plugged with debris.
(6) Air ingested into oil due to broken or cracked
oil pump pick up.
(7) Worn valve guides.
(8) Rocker arm ears contacting valve spring
retainer.
(9) Rocker arm loose, adjuster stuck or at maxi-
mum extension and still leaves lash in the system.
(10) Faulty lash adjuster.
a. Check lash adjusters for sponginess while
installed in cylinder head. Depress part of rocker
arm over adjuster. Normal adjusters should feel very
firm. Spongy adjusters can be bottomed out easily.
b. Remove suspected lash adjusters, and disassem-
bleDo not reuse retainer caps. Do not inter-
change parts and make sure that care and
cleanliness is exercised in the handling of parts.
c. Clean out dirt and varnish with solvent.
d. Reassemble with engine oil.
e. Check for sponginess.
f. If still spongy, replace with new adjuster.
INSPECTION (ENGINE OIL LEAKS IN GENERAL)
Begin with a through visual inspection of the
engine, particularly at the area of the suspected leak.
If an oil leak source is not readily identifiable, the
following steps should be followed:
(1) Do not clean or degrease the engine at this
time because some solvents may cause rubber to
swell, temporarily stopping the leak.
9 - 8 ENGINENS
DIAGNOSIS AND TESTING (Continued)
ENGINE DIAGNOSISÐPERFORMANCE
CONDITION POSSIBLE CAUSE CORRECTION
ENGINE WILL NOT START 1. Weak battery. 1. Test battery. Charge or replace
as necessary.Refer to Group 8A,
Battery.
2. Corroded or loose battery
connections.2. Clean and tighten battery
connections. Apply a coat of light
mineral grease to terminals.
3. Faulty starter. Test starting system. Refer to Group
8B, Starting.
4. Moisture on ignition wires. 4. Remove moisture from wires.
5. Faulty ignition cables. 5. Replace any cracked or shorted
cables.
6. Faulty coil or control unit. 6. Test and replace as needed.
Refer to Group 8D, Ignition System
7. Incorrect spark plug gap. 7. Set gap. Refer to Group 8D,
Ignition System.
8. Contamination in fuel system. 8. Clean system and replace fuel
filter.
9. Faulty fuel pump. 9. Test fuel pump and replace as
needed. Refer to Group 14, Fuel
System.
ENGINE STALLS OR IDLES
ROUGH1. Idle speed too low. 1. Test minimum air flow. Refer to
Group 14, Fuel System.
2. Incorrect fuel mixture. 2. Refer to Group 14, Fuel System.
3. Intake manifold leakage. 3. Inspect intake manifold, manifold
gasket, and vacuum hoses. Refer to
Group 11, Exhaust System and
Intake Manifold.
4. Incorrect ignition wiring. 4. Install correct wiring.
5. Faulty coil(s) 5. Test and replace as necessary.
Refer to Group 8D, Ignition System.
ENGINE LOSS OF POWER 1. Dirty or incorrectly gapped plugs. 1. Clean plugs and set gap. Refer to
Group 8D, Ignition System.
2. Contamination in fuel system. 2. Clean system and replace fuel
filter.
3. Faulty fuel pump. 3. Test and replace as necessary.
Refer to Group 14, Fuel System.
4. Incorrect valve timing. 4. Correct valve timing.
5. Leaking cylinder head gasket. 5. Replace cylinder head gasket.
6. Low compression. 6. Test compression of each
cylinder.
7. Burned, warped, or pitted valves. 7. Replace valves.
8. Plugged or restricted exhaust
system.8. Install new parts, as necessary.
9. Faulty ignition cables. 9. Replace any cracked or shorted
cables.
10. Faulty coil(s). 10. Test and replace as necessary.
Refer to Group 8D, Ignition System.
9 - 10 ENGINENS
DIAGNOSIS AND TESTING (Continued)
ENGINE DIAGNOSISÐMECHANICAL
CONDITION POSSIBLE CAUSES CORRECTION
NOISY VALVES 1. High or low oil level in
crankcase.1. Check for correct oil level.
2. Thin or diluted oil. 2. Change oil to correct viscosity.
3. Low oil pressure. 3. Check engine oil level.
4. Dirt in tappets/lash adjusters. 4. Replace rocker arm/hydraulic
lash adjuster assembly.
5. Worn rocker arms. 5. Inspect oil supply to rocker arms.
6. Worn tappets/lash adjusters. 6. Install new rocker arm/hydraulic
lash adjuster assembly.
7. Worn valve guides. 7. Ream and install new valves with
oversize stems.
8. Excessive runout of valve seats
on valve faces.8. Grind valve seats and valves.
9. Missing adjuster pivot. 9. Replace rocker arm/hydraulic
lash adjuster assembly.
CONNECTING ROD NOISE 1. Insuffient oil supply. 1. Check engine oil level.
2. Low oil pressure. 2. Check engine oil level. Inspect oil
pump relief valve and spring.
3. Thin or diluted oil. 3. Change oil to correct viscosity.
4. Excessive bearing clearance. 4. Measure bearings for correct
clearance. Repair as necessary.
5. Connecting rod journal
out-of-round.5. Replace crankshaft or grind
surface.
6. Misaligned connecting rods. 6. Replace bent connecting rods.
MAIN BEARING NOISE 1. Insufficient oil supply. 1. Check engine oil level.
2. Low oil pressure. 2. Check engine oil level. Inspect oil
pump relief valve and spring.
3. Thin or diluted oil. 3. Change oil to correct viscosity.
4. Excessive bearing clearance. 4. Measure bearings for correct
clearance. Repair as necessary.
5. Excessive end play. 5. Check thrust bearing for wear on
flanges.
6. Crankshaft journal out-of-round
or worn.6. Replace crankshaft or grind
journals.
7. Loose flywheel or torque
converter.7. Tighten to correct torque.
OIL PRESSURE DROP 1. Low oil level. 1. Check engine oil level.
2. Faulty oil pressure sending unit. 2. Install new sending unit.
3. Low oil pressure. 3. Check sending unit and main
bearing oil clearance.
4. Clogged oil filter. 4. Install new oil filter.
5. Worn parts in oil pump. 5. Replace worn parts or pump.
6. Thin or diluted oil. 6. Change oil to correct viscosity.
7. Excessive bearing clearance. 7. Measure bearings for correct
clearance.
8. Oil pump relief valve stuck. 8. Remove valve and inspect, clean,
or replace.
9. Oil pump suction tube loose. 9. Remove oil pan and install new
tube or clean, if necessary.
10. Oil pump cover warped or
cracked.10. Install new oil pump.
9 - 12 ENGINENS
DIAGNOSIS AND TESTING (Continued)
CONDITION POSSIBLE CAUSES CORRECTION
OIL LEAKS 1. Misaligned or deteriorated
gaskets.1. Replace gasket(s).
2. Loose fastener, broken or porous
metal part.2. Tighten, repair or replace the
part.
3. Misaligned or deteriorated cup or
threaded plug.3. Replace as necessary.
OIL CONSUMPTION OR SPARK
PLUGS FOULED1. PCV system malfunction. 1. Check system and repair as
necessary. Refer to Group 25,
Emission Control Systems.
2. Worn, scuffed or broken rings. 2. Hone cyinder bores. Install new
rings.
3. Carbon in oil ring slots. 3. Install new rings.
4. Rings fitted too tightly in grooves. 4. Remove rings and check
grooves. If groove is not proper
width, replace piston.
5. Worn valve guides. 5. Ream guides and replace valves
with oversize valves and seals.
6. Valve stem seal unseated or
faulty.6. Repair or replace seal.
NSENGINE 9 - 13
DIAGNOSIS AND TESTING (Continued)
ENGINE ASSEMBLY
REMOVAL
(1) Perform fuel pressure release procedure. Refer
to Group 14, Fuel System for procedure. Remove fuel
line to fuel rail.
(2) Disconnect battery.
(3) Remove Air cleaner and hoses.
(4) Drain cooling system. Refer to Group 7, Cooling
System for procedure.
(5) Remove upper radiator hose and remove radia-
tor fans. Refer to Group 7, Cooling System for proce-
dure.
(6) Remove lower radiator hose.
(7) Disconnect automatic transmission cooler lines
and plug, if equipped.
(8) Disconnect transmission shift linkage.
(9) Disconnect throttle body linkage.
(10) Disconnect engine wiring harness.
(11) Disconnect heater hoses.
(12) Discharge Air Conditioning System. Refer to
Group 24, Air Conditioning for procedure.
(13) Hoist vehicle and remove right inner splash
shield. Remove wheels and tires.
(14) Loosen power steering belt for pump removal.
Refer to Group 7, Cooling System for procedure.
(15) Remove axle shafts. Refer to Group 2, Suspen-
sion and Driveshafts for procedure.
(16) Disconnect exhaust pipe from manifold.
(17) Remove front and rear engine mount brackets
from the body.
(18) Remove bending braces and front engine
mount bracket. Remove transmission inspection
cover.
(19) Mark flexplate to torque converter and
remove torque converter bolts.
(20) Install front engine mount bracket.
(21) Lower vehicle.
(22) Remove power steering pump. Set pump
aside.
(23) Remove A/C lines at compressor and cap.
(24) Remove ground straps to body.
(25) Raise vehicle enough to allow engine dolly
Special Tool 6135, cradle Special Tool 6710 with
Posts Special Tool 6848 and Adaptor Special Tool
8130 to be installed under vehicle (Fig. 27).
(26) Loosen cradle posts to allow movement for
proper positioning. Locate two rear posts (right side
of engine) into the holes on the engine bedplate.
Locate the two front posts (left side of engine) on the
front engine bracket and A/C compressor bracket
(Fig. 27). Lower vehicle and position cradle mounts
until the engine is resting on mounts. Tighten
mounts to cradle frame. This will keep mounts from
moving when removing or installing engine and
transmission.(27) Lower vehicle so the weight ofONLY THE
ENGINE AND TRANSMISSIONare on the cradle.
(28) Remove engine and transmission mount bolts.
(29) Raise vehicle slowly. It may be necessary to
move the engine/transmission assembly on the cradle
to allow for removal around the body.
INSTALLATION
(1) Position engine and transmission assembly
under vehicle and slowly lower the vehicle over the
engine and transmission.
(2) Align engine and transmission mounts to
attaching points. Install mounting bolts at the right
engine and left transmission mounts. Refer to proce-
dures outlined in this section.
(3) Slowly raise vehicle enough to remove the
engine dolly and cradle Special Tools 6135 and 6710.
(4) Install axle shafts. Refer to Group 2, Suspen-
sion and Driveshafts for procedure.
(5) Install transmission and engine braces and
splash shields.
(6) Connect exhaust system to manifold. Refer to
Group 11, Exhaust System and Intake Manifold for
procedure and torque specifications.
(7) Install power steering pump. Refer to Cooling
System Group 7, Accessory Drive Section for belt ten-
sion adjustment.
(8) Install A/C compressor hoses. Refer to Group
24, Heater and Air Conditioning for procedure.
(9) Install accessory drive belts. Refer to Group 7,
Cooling System Accessory Drive Section for belt ten-
sion adjustment.
(10) Install front and rear engine mounts. Refer to
this section for procedure.
(11) Install inner splash shield. Install wheels and
tires.
(12) Connect automatic transmission cooler lines,
and shift linkage. Refer to Group 21, Transmission
for procedures.
(13) Connect fuel line and heater hoses.
(14) Install ground straps. Connect engine and
throttle body connections and harnesses. Refer to
Group 8, Electrical for procedure.
(15) Connect throttle body linkage. Refer to Group
14, Fuel System for procedure.
(16) Install radiator fans. Install radiator hoses.
Fill cooling system. Refer to Group 7, Cooling System
for filling procedure.
(17) Connect battery.
(18) Install air cleaner and hoses.
(19) Install oil filter. Fill engine crankcase with
proper oil to correct level.
(20) Start engine and run until operating temper-
ature is reached.
(21) Adjust transmission linkage, if necessary.
9 - 26 2.4L ENGINENS
REMOVAL AND INSTALLATION (Continued)