Chrysler New Yorker. Manual - part 231

ENGINE DIAGNOSIS

INDEX

page

DIAGNOSIS AND TESTING

LEAKAGE TEST . . . . . . . . . . . . . . . . . . . . . . . . 8

CYLINDER COMPRESSION TEST . . . . . . . . . . . . 7
ENGINE DIAGNOSIS—MECHANICAL . . . . . . . . . 12
ENGINE DIAGNOSIS—PERFORMANCE . . . . . . . 11

GENERAL INFORMATION . . . . . . . . . . . . . . . . . . 7
INSPECTION (ENGINE OIL

LEAKS IN GENERAL) . . . . . . . . . . . . . . . . . . . 10

INTAKE MANIFOLD LEAKAGE DIAGNOSIS . . . . . 7
LASH ADJUSTER

(TAPPET) NOISE DIAGNOSIS . . . . . . . . . . . . . . 9

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 engine RPM’S change, the area of the sus-

pected 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 loosen 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 abnormal
firing indicators fouled, hot, oily, etc. Identify cylinder
number of each spark plug for future reference.

c. Disconnect the coil connector for Direct Ignition

System (DIS) systems, or for coil-over-plug ignitions
remove the ASD relay.

d. Be sure throttle blade is fully open during the

compression check.

e. Insert compression gauge adaptor into the #1

spark plug hole in cylinder head. Crank engine until
maximum pressure is reached on gauge. 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 with
the cylinder(s) in question.

300M

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.

(6) Connect spark plug wires and ignition coil electri-

cal connector on DIS systems. Install ignition coils and
connect electrical connector on coil-over-plug systems.

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 seating).

• 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, with 552 kPa (80 psi) rec-
ommended.

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 per cylinder.

FOR EXAMPLE: At 552 kPa (80 psi) input pres-

sure, a minimum of 414 kPa (60 psi) should be main-
tained in the cylinder.

9 - 8

ENGINE

300M

DIAGNOSIS AND TESTING (Continued)

LASH ADJUSTER (TAPPET) NOISE DIAGNOSIS

LASH ADJUSTER (TAPPET) NOISE

POSSIBLE CAUSES

CORRECTION

1. Engine oil level—too high or too low. This may cause
aerated oil to enter the adjusters and cause them to be
spongy.

1. Check and correct engine oil level.

2. Insufficient running time after rebuilding cylinder
head.

2. Low speed running of up to 1 hour may be required
to fully evacuate trapped air from the valve train
system. 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.

3. Air trapped in lash adjuster (after 1 hour run time).

3. See below:

(a) Check lash adjusters for sponginess while installed
in cylinder head. Depress part of rocker arm over
adjuster. Normal adjusters should feel very firm. Very
spongy adjusters can be bottomed out easily.

(b) Before proceeding, check for and perform any
applicable Technical Service Bulletin for this condition.

4. Low oil pressure

4. See below:

(a) Check and correct engine oil level.

(b) Check engine oil pressure.

(d) Check for worn oil pump.

5. Oil passage to cylinder head(s) plugged with debris.

5. Check cylinder head oil passages and cylinder head
gasket restrictor for blockage. Clean or replaced as
necessary.

6. Worn valve guide(s).

6. Ream guide(s) and replace valve(s) with oversize
valves and seal(s).

7. Air injested into oil due to broken or cracked oil
pump pickup tube.

7. Inspect pickup tube and replace as necessary.

8. Collapsed lash adjuster due to debris injestion.

8. Clean debris from engine and replace lash
adjuster/rocker assembly*.

9. Intake rocker arm’s roller clevis ear(s) contacting
camshaft bearing journal(s) on side.

9. Inspect camshaft end play and all valve train
components for wear. Replace as necessary.

*The 3.2/3.5L engine lash adjusters are serviced with the rocker arms, do not disassemble.

300M

ENGINE

9 - 9

DIAGNOSIS AND TESTING (Continued)

INSPECTION (ENGINE OIL LEAKS IN GENERAL)

Begin with a thorough 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.

(4) If dye is not observed, drive the vehicle at var-

ious speeds for approximately 24 km (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.

9 - 10

ENGINE

300M

DIAGNOSIS AND TESTING (Continued)

Content .. 229 230 231 232 ..