Pump Circuit; Choke Circuit; Model 2Se Carburetor—Pump Circuit; Model 2Se Carburetor—Choke Circuit - Jeep J-10 Series 1982 Technical & Service Manual

Pump Circuit
When the throttle is opened suddenly, airflow re
sponse through the carburetor is almost immediate.
There is a brief time lag before fuel inertia is overcome.
This lag causes the desired air/fuel ratio to be leaned-
out.
A piston-type accelerating pump assembly mechani
cally supplies the fuel necessary to overcome this defi
ciency (fig. U-25). Fuel is forced into the pump cylinder
from the fuel bowl past the pump piston on the upward
movement of the accelerator pump shaft. As the throttle
lever is moved, the pump link, operating through a sys
tem of levers and assisted by the pump drive spring,
PUMP ROD
(ACTUATED BY
THROTTLE LEVER
PUMP DISCHARGE
SPRING AND BALL
RETAINER
PUMP SUCTION
BREAKER
PUMP DISCHARGE
SPRING AND BALL
UNSEATED)
PUMP LEVER
D.SCHARGE ™™*ETUR"
PASSAGE WKHW" 90654
Fig. U-25 Model 2SE Carburetor—Pump Circuit
INTERMEDIATE
CHOKE LEVER
COIL TANG
AND SLEEVE
CHOKE
COIL LEVER
INTERMEDIATE
CHOKE
ROD
ADJUSTMENT
SCREW
CHOKE
LEVER
FUEL SYSTEMS 1J-15
pushes the pump piston down. Fuel is forced through a
passage, past the pump discharge check ball, and out the
pump discharge jets in the venturi cluster.
Choke Circuit
The choke valve, located in the air horn assembly,
provides a high vacuum, both above and below the
throttle valves, when it is closed. During engine start
ing, vacuum above the throttle valve causes fuel to flow
from the main metering and idle circuits and provides
the richer air/fuel mixture ratio needed for cold engine
starting (fig. 1J-26).
The choke shaft is connected by linkage to a bimetallic
coil located within the choke cover. This coil winds up
(contracts) when cold and unwinds (expands) when
heated. When cold, the tension of the coil holds the
choke valve closed. When the engine starts, manifold
vacuum is applied to the diaphragm assembly to open
the choke valve slightly. This is referred to as the initial
choke valve clearance.
The carburetor has an adjustment screw located in
the primary throttle lever for fast idle speed adjust
ment. A separate adjustment screw, located in the
throttle body, is used to adjust the curb, or base (de
pending upon application), idle speed (solenoid de
energized).
NOTE: Special rivets and conventional retainers are
used to maintain the factory adjustment of the bimetal
lic choke coil. They provide a tarnper-resistant enclosure
to discourage indiscriminate readjustment in the field.
VACUUM
BREAK LEVER
CHOKE VALVE
AIR VALVE ROD
VACUUM BREAK ROD
VACUUM BREAK
AND AIR VALVE
CONTROL DIAPHRAGM
SECONDARY LOCKOUT
LEVER
90655
Fig. U-26 Model 2SE Carburetor—Choke Circuit