Jeep UNIVERSAL CJ-2A - Page 101

F
FUEL SYSTEM
(Fig. 125.). With the throttle valve seated in car-
buretor bore, press down on the upper end of
diaphragm shaft until the diaphragm bottoms
in the vacuum chamber. The metering rod should
now seat on casting with the metering rod
arm flat against the pump lifter link. If the meter-
ing rod does not seat on the casting (check by
pressing downward on metering rod) or seats be-
fore the metering rod arm makes flat contact with
the pump lifter link, make adjustment by bending
the .lip on the metering rod arm.
F" -21. Choke Circuit
The choke circuit consists of a manually-operated
choke valve, a fast-idle connecting rod, and a fast-
idle arm. The choke valve is offset-spring loaded
to prevent over-choking during the starting warm-
up period. When the choke valve is moved to a
closed position for starting, the fast idle connector
rod A in Fig. 126 revolves the fast idle link B. This
action increases the engine idle speed to prevent
stalling during the warm-up period. A fast-idle
connector rod return spring prevents partial closing
of the choke valve.
FIG. 126-FAST IDLE ADJUSTMENT
F"-22. Fast Idle Adjustment
With the choke held in wide open position, lip A
(Fig. 126) on the fast-idle rod should contact the
boss on the body casting. Adjust by bending the
fast-idle link at offset B.
F"-23. Accelerating Pump Circuit
The accelerating pump circuit shown in Fig. 127
provides a measured amount of fuel for rapid
acceleration and smooth engine operation when
the throttle is opened at lower speeds. In operation,
vacuum is applied to the underside of diaphragm
100
at all times when the engine is running. Lower
and more uniform vacuum is provided by vacuum
restriction and vacuum bleed passage. When the
diaphragm is in its maximum down position at
low throttle resulting from high vacuum in chamber
the chamber above the diaphragm is full of fuel
which has been admitted through intake passage.
When the throttle is opened, vacuum drops in the
chamber and the diaphragm is initially forced
upward by the spring on the diaphragm shaft.
The upward motion is picked up by accelerator
pump lifter which is connected to the throttle.
This movement forces fuel from the chamber
above the diaphragm through discharge pump
check valve and discharge pump jet. This auxiliary
discharge of fuel supplies engine requirements for
quick acceleration and heavy loads. When the
throttle is closed, the diaphragm is again pulled
down by high vacuum and another measured
charge of fuel enters the chamber above the
diaphragm through the intake passage to be
available for the next cycle of operation.
Note: The pump jet (see insert drawing in Fig. 12 7)
projecting into the air stream is permanently
pressed into the carburetor body and should not
be removed. Also, carburetor design makes it im-
possible to adjust the pump stroke.
FIG. 127--ACCELERATING PUMP CIRCUIT
1-Pump Fuel Passage
2-Discharge Pump Jet
3-Pump Check Valve Ball
4-Ball Check Weight
5-Pump Lifter Arm
6-Filter Screen
7-lntake Passage
8-Diaphragm
9-Vacuum Chamber
10-Vacuum Restriction jet
11-Vacuum Bleed Passage
F" -24. Accelerating Pump Maintenance
If engine acceleration is unsatisfactory, remove the
pump diaphragm and check the diaphragm for wear
or damage. Then remove the pump check retainer
ring lQcated directly above the pump check weight
and pump ball check. Pump ball check must seat
properly as a leak will cause poor acceleration