Jeep Cherokee 1977, Руководство пользователя

Страница: 111 / 136

Transmission Controlled Spark (TCS)
System
This system is standard on all California CJ models with V-8
engines and all California CJ models with six-cylinder en­
gines and automatic transmissions. It is also standard on six
and eight cylinder CJ's with automatic transmissions de­
signed for use at atitudes above 4,000 feet. The TCS system 1s
required to meet regulations for oxides of nitrogen and re­
duces them and hydrocarbon emissions by controlling vac­
uum spark advance. A solenoid switch on the manual
transmission regulates the vacuum signal to the distributor.
The TCS system needs no periodic maintenance.
Vacuum Throttle Modulator System
This system is used on Cherokee, Wagoneer, and Truck
models with V-8 engines and manual transmission and, in
California. on all Cherokee, Wagoneer. and Truck models to
help control hydrocarbon emissions during deceleration
when manifold vacuum ,s higher than at ,die. A special valve
senses this higher vacuum and activates a vacuum dia­
phragm modulator unit, which ,s mounted on the carburetor.
causing it to open the throttle slightly beyond the normal idle
setting. This throttle opening causes a slight pulsation of the
accelerator pedal which is normal. No maintenance ,s
required.
Positive Crankcase Ventilation (PCV)
System
The PCV system is used on all Jeep engines to eliminate the
�mission of crankcase fumes into the atmosphe·e by recircu­
lating these fumes back into the engine for burning. �amte­
nance consists of cleaning the urethane filter inside the small
plastic container located within the air cleaner housing. Use
kerosene as a cleaning agent. This service ,s required only on
six-cylinder engines and should be performed every 30,000
miles for CJ models and every 15.000 miles for Cherokee.
Wagoneer. and Truck models
Fuel Evaporative Control (FEC) System
This system is used on all CJ models and on Cherokee.
Wagoneer, and Truck models retailed in the State of Caltfor-
nia A charcoal canister storage system absorbs fuel tank
�
vapors and
.
vents them into the engine 1nduct1on system. An .. ·•
air cleaner purge for the canister. which works off of carbu-
retor airflow. results m minimum purging at low speeds with
a gradual increase at higher speeds.
Fuel Return Line
A return line ,s standard on all models to route fuel vapors
back to the fuel tank to prevent excessive vaporization m the
109