Fuel Systems Maintenance; Distributor Advance Mechanism; Fuel Filter - Jeep 1979 CJ-5 Technical & Service Manual

11-18
GENERAL SERVICE AND DIAGNOSIS
Fig. 1 A - 7 Timing Mark Location—Eight-Cylinder Engine
damper eccentricity. Ignition timing can then be read
from a meter or computer printout, depending on the
manufacturer's equipment.
The socket is located at 9.5° ATDC, and the equipment
is calibrated for this reading. Do not use the probe
location to check timing using a conventional timing
light,
riming Procedure
(1) Disconnect distributor vacuum hose.
(2) Connect ignition timing light and properly cali-
brated tachometer.
NOTE: If the timing light has an advance control fea-
ture, turn the control of the Off position.
(3) Start engine.
(4) Adjust idle speed to 500 rpm.
(5) Adjust initial ignition timing to setting specified
on the Tune-Up Specifications—On Vehicle chart by
loosening distributor holddown clamp and rotating
distributor.
(6) Tighten distributor holddown clamp and verify
ignition timing."
Distributor Advance Meehinlsm
Adjustable Advance Control Timing Light Procedure
(1) Disconnect TCS solenoid vacuum valve wires, if
equipped.
(2) Increase engine speed to 2000 rpm.
(3) Turn advance control of ignition timing light
until ignition timing has returned to initial setting. De-
gree reading on advance meter should be as specified in
Tune-Up Specifications—On Vehicle chart.
(4) If total advance at 2000 rpm is less than speci-
fied, disconnect vacuum advance hose at distributor.
(5) Check maximum centrifugal degrees advance at
engine rpm specified. Refer to Distributor Curves in
Specifications.
If the centrifugal advance degrees are as specified,
replace the vacuum unit.
Distributor Advance—On Tester
Distributor advance also may be tested with the dis-
tributor out of the vehicle. Follow distributor test equip-
ment manufacturer's instructions.
Information given in the Distributor Curves is for on-
vehicle testing. If the distributor advance is checked on a
distributor tester, convert the information in the Dis-
tributor Curves from engine rpm to distributor rpm and
from engine degrees to distributor degrees. Divide en-
gine rpm by 2 to obtain distributor rpm. Divide engine
degrees advance by 2 to obtain distributor degrees ad-
vance. For instance, if the Distributor Curve indicates 8
to 12 degrees advance at 2000 rpm, the corresponding
on-tester specifications would be 4 to 6 degrees advance
at 1000 rpm.
NOTE: The inches of vacuum reading is the same,
regardless if test is on-engine or off-engine.
FUEL SYSTEIS
General Inspection
Fuel systems depend on hoses and tubing to carry
liquid fuel, fuel vapors and vacuum. Fuel vapor and
vacuum leaks upset the operation of the engine and may
reduce the effectiveness of emission control devices. Liq-
uid fuel leaks not only waste fuel but also create a fire
hazard. Carefully inspect hoses and tubing for cracks,
dents, corrosion and unintentional bends. Inspect fit-
tings for corrosion or looseness. Inspect fuel tank for
leaks caused by loose mounting straps, broken seams,
dents or corrosion. Check filler neck grommets and
hoses.
Air Cleaner
Replace the dry-type air cleaner element at each preci-
sion tune-up. Under extreme conditions, more frequent
replacement is recommended.
Fill Filter
All Jeep vehicles have two fuel filters. The in-tank
filter is designed to be maintenance-free. The in-line
filter between the fuel pump and carburetor requires
periodic replacement. When installing the replacement
filter, be careful to position the fuel return nipple at the
top of the filter.