Chrysler New Yorker. Manual — part 203
ENGINE DIAGNOSIS
INDEX
page
page
DIAGNOSIS AND TESTING
LEAKAGE TEST . . . . . . . . . . . . . . . . . . . . . . . . 8
CYLINDER COMPRESSION TEST . . . . . . . . . . . . 7
ENGINE DIAGNOSIS—MECHANICAL . . . . . . . . . 11
ENGINE DIAGNOSIS—PERFORMANCE . . . . . . 10
GENERAL 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 not detected and remedied by
routine maintenance.
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 Diagnosis—Mechanical Chart
and the Service Diagnosis—Performance 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:
• Cylinder Compression Pressure Test
• Cylinder Combustion Pressure Leakage Test
• Engine Cylinder Head Gasket Failure Diagnosis
• Intake 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 TEST
(1) Before performing a cylinder compression test.
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.
(2) Check engine oil level and add oil if necessary.
(3) Drive the vehicle until engine reaches normal
operating temperature.
(4) Select a route free from traffic and other forms
of congestion, observe all traffic laws, and accelerate
through the gears several times briskly.
CAUTION:
Do not overspeed the engine. The
higher engine speed may help clean out valve seat
deposits which can prevent accurate compression
readings.
a. Clean the spark plug recesses with compressed
air.
b. 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.
c. Disconnect the coil connector for Direct Ignition
System (DIS).
d. Be sure throttle blade is fully open during the
compression check.
e. 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.
f. Repeat Step e for all remaining cylinders.
g. Compression should not be less than (689kPa)
100 psi and not vary more than 25 percent from cyl-
inder to cylinder.
h. If one or more cylinders have abnormally low
compression pressures, repeat steps 4e through 4g.
i. 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.
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ENGINE
9 - 7
NOTE:
The recommended compression pressures
are to be used only as a guide to diagnosing engine
problems. An engine should not be disassembled to
determine the cause of low compression unless
some malfunction is present.
(5) Clean or replace spark plugs as necessary and
adjust gap as specified in Electrical Group 8. Tighten
to specifications.
CYLINDER COMBUSTION PRESSURE LEAKAGE
TEST
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
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) Oil passage to the cylinder head(s) is plugged
with debris.
(6) Air ingested into oil due to broken or cracked
oil pump pickup.
(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.
NOTE: On the 3.2L engine, the lash adjuster is ser-
viced with the rocker arm, do not disassemble.
b. Remove suspected lash adjusters, and disassem-
ble Do 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.
(2) Add an oil soluble dye (use as recommended by
manufacturer). Start the engine and let idle for
approximately 15 minutes. Check the oil dipstick to
make sure the dye is thoroughly mixed as indicated
with a bright yellow color under a black light.
(3) Using a black light, inspect the entire engine
for fluorescent dye, particularly at the suspected area
of oil leak. If the oil leak is found and identified,
repair per service manual instructions.
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ENGINE
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DIAGNOSIS AND TESTING (Continued)
(4) If dye is not observed, drive the vehicle at var-
ious speeds for approximately 24km (15 miles), and
repeat inspection.
(5) If the oil leak source is not positively
identified at this time, proceed with the air leak
detection test method as follows:
• Disconnect the fresh air hose (makeup air) at
the cylinder head cover and plug or cap the nipple on
the cover.
• Remove the PCV valve hose from the cylinder
head cover. Cap or plug the PCV valve nipple on the
cover.
• Attach an air hose with pressure gauge and reg-
ulator to the dipstick tube.
CAUTION:
Do not subject the engine assembly to
more than 20.6 kpa (3 PSI) of test pressure.
• Gradually apply air pressure from 1 psi to 2.5
psi maximum while applying soapy water at the sus-
pected source. Adjust the regulator to the suitable
test pressure that provide the best bubbles which
will pinpoint the leak source. If the oil leak is
detected and identified, repair per service manual
procedures.
• If the leakage occurs at the rear oil seal area,
refer to the section, Inspection for Rear Seal Area
Leak.
(6) If no leaks are detected, turn off the air supply
and remove the air hose and all plugs and caps.
Install the PCV valve and breather cap hose. Proceed
to next step.
(7) Clean the oil off the suspect oil leak area using
a suitable solvent. Drive the vehicle at various
speeds approximately 24 km (15 miles). Inspect the
engine for signs of an oil leak by using a black light.
INSPECTION FOR REAR SEAL AREA LEAKS
Since it is sometimes difficult to determine the
source of an oil leak in the rear seal area of the
engine, a more involved inspection is necessary. The
following steps should be followed to help pinpoint
the source of the leak.
If the leakage occurs at the crankshaft rear oil seal
area:
(1) Disconnect the battery.
(2) Raise the vehicle.
(3) Remove torque converter or clutch housing
cover and inspect rear of block for evidence of oil.
Use a black light to check for the oil leak. If a leak is
present in this area remove transmission for further
inspection.
(a) Circular spray pattern generally indicates
seal leakage or crankshaft damage.
(b) Where leakage tends to run straight down,
possible causes are a porous block, oil galley cup
plug, bedplate to cylinder block mating surfaces
and seal bore. See proper repair procedures for
these items.
(4) If no leaks are detected, pressurized the crank-
case as outlined in the, Inspection (Engine oil Leaks
in general)
CAUTION:
Do not exceed 20.6 kPa (3 psi).
(5) If the leak is not detected, very slowly turn the
crankshaft and watch for leakage. If a leak is
detected between the crankshaft and seal while
slowly turning the crankshaft, it is possible the
crankshaft seal surface is damaged. The seal area on
the crankshaft could have minor nicks or scratches
that can be polished out with emery cloth.
CAUTION: Use extreme caution when crankshaft
polishing is necessary to remove minor nicks and
scratches. The crankshaft seal flange is especially
machined to complement the function of the rear oil
seal.
(6) For bubbles that remain steady with shaft
rotation, no further inspection can be done until dis-
assembled.
(7) After the oil leak root cause and appropriate
corrective action have been identified. Refer to Rear
Crankshaft Seals, for proper replacement procedures.
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ENGINE
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DIAGNOSIS AND TESTING (Continued)
ENGINE DIAGNOSIS—PERFORMANCE
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.
3. Test starting system. Refer to Group 8B,
Starting.
4. Faulty coil(s) or control unit.
4. Test and replace as needed. Refer to
Group 8D, Ignition System.
5. Incorrect spark plug gap.
5. Set gap. Refer to Group 8D, Ignition
System.
6. Contamination in fuel system.
6. Clean system and replace fuel filter.
7. Faulty fuel pump.
7. Test fuel pump and replace as needed.
Refer to Group 14, Fuel System.
8. Incorrect engine timing.
8. Check for a skipped timing belt/chain or
a loose camshaft sprocket (3.2/3.5L).
ENGINE STALLS OR
IDLES ROUGH
1. 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. Faulty coil(s).
4. 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 coil(s).
9. Test and replace as necessary. Refer to
Group 8D, Ignition System.
ENGINE MISSES ON
ACCELERATION
1. Dirty or incorrectly gapped spark plugs.
1. Clean spark plugs and set gap. Refer to
Group 8D, Ignition System.
2. Contamination in Fuel System.
2. Clean fuel system and replace fuel filter.
3. Burned, warped, or pitted valves.
3. Replace valves.
4. Faulty coil(s).
4. Test and replace as necessary. Refer to
Group 8D, Ignition System.
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ENGINE
LH
DIAGNOSIS AND TESTING (Continued)
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