Chrysler 1998 Voyager, Service Manual, Page: 1058 / 1938

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:
•
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) 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-
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.
9 - 8 ENGINE
NS
DIAGNOSIS AND TESTING (Continued)