Cylinder Combustion Pressure Leakage Test; Cylinder Head Gasket Failure Diagnosis - Jeep 1987 Wrangler Workshop Manual

EN011ES
GENERAL SERVICE AND DIAGNOSIS
Insert a compression pressure gauge and rotate
the engine with the starter motor for three
revolutions.
Record the compression pressure on the third
revolution. Continue the test for the remaining
cylinders.
Refer to the Specifications chart for the correct
engine compression pressures.
CYLINDER COMBUSTION PRESSURE
LEAKAGE TEST
The combustion pressure leakage test provides
an accurate means for determining engine
condition.
Combustion pressure leakage testing will
ascertain exhaust and intake valve leaks
(improper seating), leaks between adjacent
cylinders or into the water jacket, or 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
normal operating temperature, then turn the
engine O F F .
Remove the spark plugs.
Remove the oil filler cap.
Remove the air cleaner.
Position the carburetor fast idle speed adjust-
ment screw on the top step of the fast idle cam.
Calibrate the tester according to the manu-
facturer's instructions.
NOTE: The shop air source for testing should
maintain 483 kPa (70 psi) minimum, 1 379 kPa
(200 psi) maximum, and 552 kPa (80 psi)
recommended.
Perform the test procedures on each cylinder
a c c o r d i n g to the tester m a n u f a c t u r e r ' s
instructions.
NOTE: While testing, listen for pressurized air
escaping through the carburetor, 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 percent leakage. For
example, at 552 kPa (80 psi) input pressure, a
minimum of 414 k P a (60 psi) should be
maintained in the cylinder.
Refer to the Cylinder Combustion Pressure
Leakage Test Diagnosis.
CYLINDER HEAD GASKET FAILURE DIAGNOSIS
A leaking cylinder head gasket usually results in
a loss of power, loss of coolant and engine
misfire.
A cylinder head gasket leak can be located
between adjacent cylinders or between a
cylinder and the adjacent water jacket.
A cylinder head gasket leaking between two
adjacent cylinders is indicated by a loss of power
and/or engine misfire.
A cylinder head gasket leaking between a
cylinder and an adjacent water jacket is
indicated by coolant foaming or overheating and
loss of coolant.
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