Distributor Advance Mechanism Testing - Six-Cylinder; Centrifugal Advance Test; Vacuum Advance Test - Six-Cylinder - Jeep 1987 Wrangler Workshop Manual

ENGINES
ENGINE TUNE-UP PROCEDURES
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.
With the engine at idle speed, check the timing.
If necessary, adjust the timing one degree
higher than the specification listed on the
Emission Control Information label. Also, refer
to the ignition advance curve illustrations.
NOTE: With the alternate timing procedure, the
basic timing must be one degree higher than the
specification listed on the Emission Control
Information label. For example, if the timing
specification is listed as 6° ± 2° at 1600 rpm, the
alternate procedure requires 7° ± 2 ° at idle
speed.
Distributor
Adianct mechanism Testing -
Six-Cylinder OILY
Centrifugal Advance Test
Set the parking brake. Shift automatic trans-
missions to PARK and manual transmissions to
N E U T R A L
Start the engine and allow it to attain normal
operating temperature. Ensure that the A/C is
turned O F F , if equipped.
With the ignition switch O F F , disconnect the
three-wire connector from the 4-in. and 10-in.
Hg vacuum switch assembly.
D i s c o n n e c t and plug the vacuum h o s e
connected to the distributor vacuum advance
mechanism.
Connect a timing light between the No. 1 spark
plug and wire.
Connect the timing light power wire connectors
according to the manufacturer's instructions.
Connect a calibrated, expanded scale tach-
ometer to the coil negative (TACH) terminal.
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 fan. Do not wear loose clothing.
Start the engine and slowly increase the speed
while observing the timing mark and index with
the timing light.
The ignition timing should advance smoothly as
the engine speed increases. Refer to the ignition
advance curve illustrations.
If the ignition timing advances unevenly, check
and repair the centrifugal advance mechanism.
Connect the distributor vacuum advance hose
and the vacuum switch assembly three-wire
connector.
Remove the timing light and connect the No. 1
cylinder spark plug wire.
Remove the tachometer.
Vacuum Advance Test - Six-Cylinder ONLY
Set the parking b r a k e . Shift automatic
t r a n s m i s s i o n s to P A R K a n d m a n u a l
transmissions to the NEUTRAL position.
Start the engine and allow it to attain normal
operating temperature. Ensure that the A/C is
turned O F F , if equipped.
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