Ford COUGAR 1968 Shop Manual page 499

PART 10-2
-
Autolite Model
1 100 1 -V
Carburetor
FIG. 8-Automatic Choke System
-EXTERNAL VENTING
ND VALVE OUT
FUEL BOWL V
@VACUUM
FIG. 9-Fuel Bowl Venting System
ing of the choke plate. As the throt-
tle is returned to the idle position,
the pulldown rod opens the choke
plate mechanically to a calibrated
setting. The fast idle screw, attached
to the throttle lever, increases the
engine idle speed for smoother run-
ning when the engine is cold.
During driveaway, increased air
flow will result in increased pressure
on the choke plate, causing the choke
plate to partially open against the
force of the bimetal spring, thereby
controlling fuel-air mixture in re-
sponse to engine demand.
As the engine continues to run.
manifold vacuum draws heated air
from the exhaust manifold heat cham-
ber through the 'thermostatic choke
control outlet line connected to the
choke housing. The amount of air
entering the choke housing is con-
trolled by restriction of air channels
in the carburetor.
The warmed air from the heat
chamber enters the choke housing
and heats the thermostatic spring,
causing it to warm up. Tension of
the thermostatic spring gradually de-
creases as the temperature of the air
from the heat chamber rises, allowing
the choke plate to open. The air in
the choke housing is exhausted into
the intake manifold.
When the engine reaches its nor-
mal operating temperature, the spring
exerts full tension on the choke plate,
forcing it to the full open position.
When the choke plate is partially
or fully closed. a fast idle cam is
rotated into position to contact the
fast idle adjustment screw. The screw,
attached to the throttle lever. permits
a faster engine idle speed for smoother
running when the engine is cold. The
thermostatic choke lever and torsion
spring rotates the fast idle cam to
lower the engine idle speed when the
engine temperature rises and choking
is reduced.
The throttle lever and pull-down
rod partially opens the choke plate
when the accelerator pedal is fully
depressed. This permits unloading a
flooded engine.
FUEL BOWL VENT SYSTEM
The fuel bowl requires venting
(Fig. 9) to provide proper operation
for the various systems. Fuel vapors
may form in the fuel bowl when a
hot engine is stopped, idling, or op-
erating at very low speeds. By venti-
ing the fuel bowl to the atmosphere
by means of a vent control valve,
engine performance is improved. At