Dodge Dakota (R1). Manual — part 470
DIAGNOSIS AND TESTING— ENGINE DIAGNOSIS - MECHANICAL
ENGINE MECHANICAL DIAGNOSIS CHART
CONDITION
POSSIBLE CAUSES
CORRECTION
NOISY VALVES/LIFTERS
1. High or low oil level in crankcase
1. Check for correct oil level. Adjust oil
level by draining or adding as needed
2. Thin or diluted oil
2. Change oil. (Refer to 9 - ENGINE/
LUBRICATION/OIL - STANDARD
PROCEDURE)
3. Low oil pressure
3. Check engine oil level. If ok, Perform
oil pressure test. (Refer to 9 - ENGINE/
LUBRICATION - DIAGNOSIS AND
TESTING) for engine oil pressure
test/specifications
4. Dirt in tappets/lash adjusters
4. Clean/replace hydraulic tappets/lash
adjusters
5. Bent push rod(s)
5. Install new push rods
6. Worn rocker arms
6. Inspect oil supply to rocker arms and
replace worn arms as needed
7. Worn tappets/lash adjusters
7. Install new hydraulic tappets/lash
adjusters
8. Worn valve guides
8. Inspect all valve guides and replace
as necessary
9. Excessive runout of valve seats or
valve faces
9. Grind valves and seats
CONNECTING ROD
NOISE
1. Insufficient oil supply
1. Check engine oil level.
2. Low oil pressure
2. Check engine oil level. If ok, Perform
oil pressure test. (Refer to 9 - ENGINE/
LUBRICATION - DIAGNOSIS AND
TESTING) engine oil pressure
test/specifications
3. Thin or diluted oil
3. Change oil to correct viscosity. (Refer
to 9 - ENGINE/LUBRICATION/OIL -
STANDARD PROCEDURE) for correct
procedure/engine oil specifications
4. Excessive connecting rod bearing
clearance
Measure bearings for correct clearance
with plasti-gage. Repair as necessary
5. Connecting rod journal out of round
5. Replace crankshaft or grind journals
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. If ok, Perform
oil pressure test. (Refer to 9 - ENGINE/
LUBRICATION - DIAGNOSIS AND
TESTING)
3. Thin or diluted oil
3. Change oil to correct viscosity.
9 - 68
ENGINE 3.9L
AN
ENGINE 3.9L (Continued)
CONDITION
POSSIBLE CAUSES
CORRECTION
4. Excessive main bearing clearance
4. Measure bearings for correct
clearance. Repair as necessary
5. Excessive end play
5. Check crankshaft thrust bearing for
excessive wear on flanges
6. Crankshaft main journal out of round
or worn
6. Grind journals or replace crankshaft
7. Loose flywheel or torque converter
7. Inspect crankshaft, flexplate/flywheel
and bolts for damage. Tighten to correct
torque
LOW OIL PRESSURE
1. Low oil level
1. Check oil level and fill if necessary
2. Faulty oil pressure sending unit
2. Install new sending unit
3. Clogged oil filter
3. Install new oil filter
4. Worn oil pump
4. Replace oil pump assembly.
5. Thin or diluted oil
5. Change oil to correct viscosity.
6. Excessive bearing clearance
6. Measure bearings for correct
clearance
7. Oil pump relief valve stuck
7. Remove valve to inspect, clean and
reinstall
8. Oil pump suction tube loose, broken,
bent or clogged
8. Inspect suction tube and clean or
replace if necessary
9. Oil pump cover warped or cracked
9. Install new oil pump
OIL LEAKS
1. Misaligned or deteriorated gaskets
1. Replace gasket
2. Loose fastener, broken or porous
metal part
2. Tighten, repair or replace the part
3. Front or rear crankshaft oil seal
leaking
3. Replace seal
4. Leaking oil gallery plug or cup plug
4. Remove and reseal threaded plug.
Replace cup style plug
EXCESSIVE OIL
CONSUMPTION OR
SPARK PLUGS OIL
FOULED
1. CCV System malfunction
1. (Refer to 25 - EMISSIONS
CONTROL/EVAPORATIVE EMISSIONS
- DESCRIPTION) for correct operation
2. Defective valve stem seal(s)
2. Repair or replace seal(s)
3. Worn or broken piston rings
3. Hone cylinder bores. Install new rings
4. Scuffed pistons/cylinder walls
4. Hone cylinder bores and replace
pistons as required
5. Carbon in oil control ring groove
5. Remove rings and de-carbon piston
6. Worn valve guides
6. Inspect/replace valve guides as
necessary
7. Piston rings fitted too tightly in
grooves
7. Remove rings and check ring end gap
and side clearance. Replace if
necessary
AN
ENGINE 3.9L
9 - 69
ENGINE 3.9L (Continued)
DIAGNOSIS AND TESTING—ENGINE DIAGNOSIS - LUBRICATION
CONDITION
POSSIBLE CAUSES
CORRECTION
OIL LEAKS
1. Gaskets and O-Rings.
1.
(a) Misaligned or damaged.
(a) Replace as necessary.
(b) Loose fasteners, broken or
porous metal parts.
(b) Tighten fasteners, Repair or
replace metal parts.
2. Crankshaft rear seal
2. Replace as necessary.
3. Crankshaft seal flange.
Scratched, nicked or grooved.
3. Polish or replace crankshaft.
4. Oil pan flange cracked.
4. Replace oil pan.
5. Timing chain cover seal,
damaged or misaligned.
5. Replace seal.
6. Scratched or damaged vibration
damper hub.
6. Polish or replace damper.
OIL PRESSURE DROP
1. Low oil level.
1. Check and correct oil level.
2. Faulty oil pressure sending unit.
2. Replace sending unit.
3. Low oil pressure.
3. Check pump and bearing
clearance.
4. Clogged oil filter.
4. Replace oil filter.
5. Worn oil pump.
5. Replace as necessary.
6. Thin or diluted oil.
6. Change oil and filter.
7. Excessive bearing clearance.
7. Replace as necessary.
8. Oil pump relief valve stuck.
8. Clean or replace relief valve.
9. Oil pump suction tube loose or
damaged.
9. Replace as necessary.
OIL PUMPING AT RINGS; SPARK
PLUGS FOULING
1. Worn or damaged rings.
1. Hone cylinder bores and replace
rings.
2. Carbon in oil ring slots.
2. Replace rings.
3. Incorrect ring size installed.
3. Replace rings.
4. Worn valve guides.
4. Ream guides and replace valves.
5. Leaking intake gasket.
5. Replace intake gaskets.
6. Leaking valve guide seals.
6. Replace valve guide seals.
DIAGNOSIS AND TESTING—CYLINDER
COMPRESSION PRESSURE
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) Clean the spark plug recesses with compressed
air.
(2) Remove the spark plugs (Refer to 8 - ELEC-
TRICAL/IGNITION
CONTROL/SPARK
PLUG
-
REMOVAL).
(3) Secure the throttle in the wide-open position.
(4) Disconnect the ignition coil.
(5) Insert a compression pressure gauge and rotate
the engine with the engine starter motor for three
revolutions.
(6) Record the compression pressure on the third rev-
olution. Continue the test for the remaining cylinders.
(Refer to 9 - ENGINE - SPECIFICATIONS) for the
correct engine compression pressures.
9 - 70
ENGINE 3.9L
AN
ENGINE 3.9L (Continued)
DIAGNOSIS AND TESTING—CYLINDER
COMBUSTION PRESSURE LEAKAGE
The combustion pressure leakage test provides an
accurate means for determining engine condition.
Combustion pressure leakage testing will detect:
• Exhaust and intake valve leaks (improper seat-
ing)
• Leaks between adjacent cylinders or into water
jacket
• Any causes for combustion/compression pressure
loss
WARNING: DO NOT REMOVE THE RADIATOR CAP
WITH THE SYSTEM HOT AND UNDER PRESSURE.
SERIOUS
BURNS
FROM
HOT
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 OFF the
engine.
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 procedure on each cylinder accord-
ing to the tester manufacturer’s instructions. While
testing, listen for pressurized air escaping through
the throttle body, tailpipe or 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.
Refer to CYLINDER COMBUSTION PRESSURE
LEAKAGE DIAGNOSIS CHART below
CYLINDER COMBUSTION PRESSURE LEAKAGE DIAGNOSIS CHART
CONDITION
POSSIBLE CAUSE
CORRECTION
AIR ESCAPES THROUGH
THROTTLE BODY
Intake valve bent, burnt, or not
seated properly
Inspect valve and valve seat.
Reface or replace, as necessary
AIR ESCAPES THROUGH
TAILPIPE
Exhaust valve bent, burnt, or not
seated properly
Inspect valve and valve seat.
Reface or replace, as necessary
AIR ESCAPES THROUGH
RADIATOR
Head gasket leaking or cracked
cylinder head or block
Remove cylinder head and inspect.
Replace defective part
MORE THAN 50% LEAKAGE
FROM ADJACENT CYLINDERS
Head gasket leaking or crack in
cylinder head or block between
adjacent cylinders
Remove cylinder head and inspect.
Replace gasket, head, or block as
necessary
MORE THAN 25% LEAKAGE AND
AIR ESCAPES THROUGH OIL
FILLER CAP OPENING ONLY
Stuck or broken piston rings;
cracked piston; worn rings and/or
cylinder wall
Inspect for broken rings or piston.
Measure ring gap and cylinder
diameter, taper and out-of-round.
Replace defective part as necessary
STANDARD PROCEDURE—CYLINDER BORE
HONING
Before honing, stuff plenty of clean shop towels
under the bores and over the crankshaft to keep
abrasive materials from entering the crankshaft
area.
(1) Used carefully, the Cylinder Bore Sizing 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 scuff-
ing, scoring and scratches. Usually, a few strokes will
clean up a bore and maintain the required limits.
CAUTION: DO NOT use rigid type hones to remove
cylinder wall glaze.
(2) Deglazing of the cylinder walls may be done if
the cylinder bore is straight and round. Use a cylin-
der surfacing hone, Honing Tool C-3501, equipped
with 280 grit stones (C-3501-3810). about 20-60
strokes, depending on the bore condition, will be suf-
ficient to provide a satisfactory surface. Using honing
oil C-3501-3880, or a light honing oil, available from
major oil distributors.
AN
ENGINE 3.9L
9 - 71
ENGINE 3.9L (Continued)
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