Dodge Dakota Sport 2001 Service Manual page 1099

9 - 70 ENGINE 3.9L
ENGINE 3.9L (Continued)
DIAGNOSIS AND TESTING—ENGINE DIAGNOSIS - LUBRICATION
CONDITION
OIL LEAKS
OIL PRESSURE DROP
OIL PUMPING AT RINGS; SPARK
PLUGS FOULING
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.
POSSIBLE CAUSES
1. Gaskets and O-Rings.
(a) Misaligned or damaged.
(b) Loose fasteners, broken or
porous metal parts.
2. Crankshaft rear seal
3. Crankshaft seal flange.
Scratched, nicked or grooved.
4. Oil pan flange cracked.
5. Timing chain cover seal,
damaged or misaligned.
6. Scratched or damaged vibration
damper hub.
1. Low oil level.
2. Faulty oil pressure sending unit.
3. Low oil pressure.
4. Clogged oil filter.
5. Worn oil pump.
6. Thin or diluted oil.
7. Excessive bearing clearance.
8. Oil pump relief valve stuck.
9. Oil pump suction tube loose or
damaged.
1. Worn or damaged rings.
2. Carbon in oil ring slots.
3. Incorrect ring size installed.
4. Worn valve guides.
5. Leaking intake gasket.
6. Leaking valve guide seals.
(2) Remove the spark plugs (Refer to 8 - ELEC-
TRICAL/IGNITION
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.
CORRECTION
1.
(a) Replace as necessary.
(b) Tighten fasteners, Repair or
replace metal parts.
2. Replace as necessary.
3. Polish or replace crankshaft.
4. Replace oil pan.
5. Replace seal.
6. Polish or replace damper.
1. Check and correct oil level.
2. Replace sending unit.
3. Check pump and bearing
clearance.
4. Replace oil filter.
5. Replace as necessary.
6. Change oil and filter.
7. Replace as necessary.
8. Clean or replace relief valve.
9. Replace as necessary.
1. Hone cylinder bores and replace
rings.
2. Replace rings.
3. Replace rings.
4. Ream guides and replace valves.
5. Replace intake gaskets.
6. Replace valve guide seals.
CONTROL/SPARK
AN
PLUG -