Tac System—Four-Cylinder Engine - Jeep J-10 Series 1982 Technical & Service Manual

1J-80 FUEL SYSTEMS
emissions. It also improves engine performance during
warm-up and minimizes carburetor icing.
All Jeep vehicles are equipped with a vacuum-oper
ated TAC system. In addition, vehicles with six-cylinder
engines have air cleaners with trap doors that close off
the air cleaner air intake duct when the engine is turned
off. This prevents fuel vapor, etc., from escaping to the
atmosphere during the time the engine is inoperative.
The TAC system is comprised of a heat stove that is
either fully encloses the exhaust manifold (four-cylinder
engines) or partially encloses the exhaust manifold (six-
and eight-cylinder engines), a heated air tube, an air
cleaner assembly equipped with a thermal sensor, and a
vacuum motor and air valve assembly (figs. 1J-150 and
151). The air cleaner duct is attached by a flexible duct
to the ambient air inlet at the front of the engine
compartment.
AIR CLEANER
HOUSING
CHECK
VALVE
COVER
OPERATION—TAC SYSTEM
The position of the air valve is controlled by manifold
vacuum opposing spring tension. Manifold vacuum is
controlled by a thermal sensor located in the air cleaner
housing.
The sensor incorporates a vent valve that regulates
the vacuum applied to the vacuum motor and thereby
controls the air valve position. The air supply is either
all heated air, a mixture of heated and ambient air or all
ambient air from outside the vehicle. The result is that
the inlet air to the carburetor is maintained at the cor
rect temperature (fig. 1J-152).
During engine warm-up, the thermal sensor passes
vacuum to the TAC vacuum motor. The air valve is held
in the heat On position. Exhaust manifold-heated air
flows to the air cleaner. As the temperature of the in
coming air approaches the calibrated temperature, the
AMBIENT AIR
INDUCTION ASSEMBLY
Rg. 1J-150 TAC System—Four-Cylinder Engine
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