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PART 10-4 MOTORCRAFT MODEL 2100 CARBURETTOR
fuel then flows past the pointed tip of
the adjusting needle which controls
the idle fuel discharge. From the ad-
justing needle chamber, the fuel flows
through a short horizontal passage
and is discharged below the throttle
plates.
During off idle when the throt\le
plate is moved slightly past the idle
transfer holes, each hole begins dis-
charging fuel as it is exposed to man-
ifold vacuum. As the throttle plate is
opened still wider and engine speed
increases, the air flow through the
carburetor is also increased. This
creates a vacuum in the booster ven-
turi strong enough to bring the main
fuel system into operation. Fuel flow
from the idle fuel system tapers off
as the main fuel system begins dis-
charging fuel.
ACCELERATING SYSTEM
Upon acceleration, the air flow
through the carburettor responds al-
most immediately to the increased
throttle
opening.
There is, however, a
brief interval before the flowing fuel,
which is heavier than air, can gain
the required flow speed to maintain
the desired balance of fuel and air.
During the interval, the accelerating
system
(Fig.
6) supplies fuel until
the other systems can once again
provide the proper mixture.
When the throttle is closed, the
diaphragm return spring forces the
diaphragm toward the cover, drawing
fuel into the chamber through the in-
let. The inlet has an Elastomer
valve which uncovers the inlet hole
to admit fuel from the fuel bowl.
The valve covers the inlet hole when
the accelerating pump is operated to
prevent the fuel from returning to
the bowl. A discharge weight and
ball check prevents air from enter-
ing the discharge nozzle when fuel
is drawn into the diaphragm cham-
ber.
When the throttle is opened, the
diaphragm rod is forced inward, forc-
ing fuel from the chamber into the
discharge passage. Fuel under pres-
sure forces
the pump discharge
weight and ball off their seat and fuel
passes through the accelerating pump
discharge screw and is sprayed into
each main venturi through discharge
ports .
.
An air bleed in the wall of the ac-
celerating pump fuel chamber pre-
vents vapor entrapment and pressure
build-up in the diaphragm chamber.
PUMP DISCHARGE NOZZLE
BALL CHECK
PUMP DISCHARGE
. . FUEL
PUMP DISCHARGE WEIGHT
FIG. 6-Accelerating Pump System
¢=l
AIR
¢:::::1
FUEL -AIR
. . . FUEL
4pm
VACUUM
HIGH
SPEED AIR
BLEED
MAIN
WELL TUBE
ANTI-SIPHON AIR BLEED
MAIN WELL
FIG. 7-Main Fuel System
PRIMAR
Y
FUEL BOWL
10-37
82601-A
62602
-
A
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