Testing Distributor Advance Mechanisms; Adjustable Advance Control Timing Light Procedure; Testing Distributor Advance Mechanisms - Off Engine - Jeep J-10 Series 1982 Technical & Service Manual

1A-20 GENERAL SERVICE AND DIAGNOSIS
Rg. 1A-7 Timing Degree Seals and Notch Location—
Eight-Cylinder Engine
WARNING: Use extreme caution when engine is oper
ating. Do not stand in direct line with fan. Do not put
hands near pulleys, belts or fan. Do not wear loose
clothing.
(4) Engage parking brake, start engine and allow to
warm up to normal operating temperature. Place auto
matic transmission in Drive, manual transmission in
Neutral position.
(5) Adjust idle speed to specified curb (slow) idle
rpm. Refer to Tune-Up Specifications charts and Emis
sion Control Information label.
WARNING: Use extreme caution when engine is oper
ating. Do not stand in direct line with fan. Do not put
hands near pulleys, belts or fan. Do not wear loose
clothing.
(6) Adjust ignition timing to degrees specified in
Tune-Up Specifications—On Vehicle chart by loosening
distributor holddown clamp and rotating distributor.
(7) For six-cylinder engines (except 49-State 6-cyl-
inder CJ) increase engine speed to 1600 rpm while ob
serving and adjusting ignition timing.
(8) Tighten distributor holddown clamp and verify
that ignition timing is correct.
(9) Turn off engine and removejiming light and
tachometer. Connect No. 1 spark plug wire, if dis
connected. Connect hose to distributor vacuum advance
mechanism. If applicable, remove jumper wire and con
nect electronic ignition module connector to wire har
ness connector.
Testing Distributor Advance Mechanisms
Adjustable Advance Control Timing Light Procedure
(1) Connect timing light and tachometer as de
scribed above. Disconnect and plug vacuum advance
hose. Connect vacuum pump (with gauge) to distributor
vacuum advance mechanism.
(2) For six-cylinder engines, disconnect two-wire
connector (yellow and black wires) at electronic ignition
module and short circuit ignition module connector ter
minals with jumper wire. This will deactivate electronic
retard circuit in module. This step does not apply to 49-
state designated CJ vehicles.
WARNING: Use extreme caution when engine is oper-
ting. Do not stand in direct line with fan. Do not put
hands near pulleys, belts or fan. Do not wear loose
clothing.
(3) Start engine and allow to warm-up to normal
operating temperature. Set parking brake, place auto
matic transmission in Drive, manual in Neutral
position.
(4) Increase engine speed to 2000 rpm. Apply 18 in.
Hg (60.8 kPa) vacuum to distributor vacuum advance
mechanism.
(5) Observe timing degree scale and turn advance
control on ignition timing light until ignition timing
(degrees BTDC) has returned to idle speed specification
(1600 rpm for six-cylinder engines). Degrees indicated
on advance meter should be total degrees advance as
specified in Distributor Curves in Specifications. Add
vacuum advance degrees at 18 in. Hg (60.8 kPa) to me
chanical advance degrees at 2000 rpm. For example, for
six-cylinder engine, total advance should be 28.5 to 39
degrees BTDC.
(6) If total advance at 2000 rpm with 18 in. Hg (60.8
kPa) vacuum applied is less than specification, dis
connect vacuum pump and, with engine at 2000 rpm,
determine maximum centrifugal degrees advance. Refer
to Distributor Curves in Specifications.
(7) If centrifugal advance degrees are within speci
fication, replace vacuum advance mechanism.
(8) Turn off engine; remove timing light and tach
ometer; remove jumper wire and connect electronic igni
tion module connector to wire harness connector (six-
cylinder engine only); and connect vacuum hose to
distributor.
Testing Distributor Advance Mechanisms—Off Engine
Total distributor advance degrees also may be deter
mined with the distributor removed from the engine.
Follow the distributor test equipment manufacturer's
instructions.
Information provided in the Distributor Curves is for
on-engine testing. If the distributor advance mecha
nisms are tested with a distributor tester, convert the
information in the Distributor Curves from engine rpm
to distributor rpm and from engine degrees advance to
distributor degrees advance. Divide engine rpm by 2 to
obtain distributor rpm. Divide engine degrees advance
by 2 to obtain distributor degrees advance. For instance,
if the Distributor Curve indicates 8 to 12 degrees ad
vance at 2000 rpm, the corresponding on-tester specifi
cations would be 4 to 6 degrees advance at 1000 rpm.