Carburetor Circuits (2150 Venturi); Carburetor Overhaul (2150 Venturi) - Jeep 1979 CJ-5 Technical & Service Manual

1J-34 FUEL SYSTEMS
CARBURETOR CIRCUITS
Altitude Compensation Circuit
The altitude compensation circuit supplies the extra
air necessary to lean out the fuel/air mixture at high
altitudes. The compensation circuit parallels the main
carburetor intake circuit (fig. 1J-63). At the top, a small
choke valve controls the airflow when the main choke is
closed. Air flows down through a passage in the main
body into a plenum chamber located adjacent to the two
main venturi bores. A spring-loaded valve regulates the
amount of air passed from the plenum into the com-
pensator body. Air flows from the compensator body
through two air passages bored into the main
V e n t u r i s .
The opening and closing of the valve in the com-
pensator body is controlled by an aneroid which is sensi-
tive to atmospheric pressure. At the lower atmospheric
pressure of high altitudes, the aneroid pushes on the end
of the compensator valve stem, opening the valve. At
lower altitudes, the aneroid relaxes, automatically clos-
ing the valve.
M E T E R E D
A I R F L O W
Fig. 1J-63 Altitude Compensation Circuit
The aneroid is factory calibrated and is not adjust-
able. Do not tamper with the hex-head plug on the
aneroid.
Choke Circuit
The compensation circuit is provided with a separate
choke valve linked directly to the main choke valve (fig.
1J-64). It is not adjustable.
A L T I T U D E
COMPENSAT80N
• CHOKE
V A L V E
Fig. 1J-64 ConpRSStloEi E t a ! ! Ctote Mm
A thermostatic coil is used to operate the choke valve
for cold engine start-up. The bimetal coil winds up when
cold and unwinds when warm. Exhaust-heated air is
provided to warm the coil as the engine warms up. An
electric coil supplies additional heat to open the choke
valve more quickly. The electric choke consists of a ce-
ramic heater in the choke coil housing. Current to oper-
ate the heater is supplied through an oil pressure
sensing switch. When the engine is operating, oil pres-
sure closes the switch to operate the choke. If the engine
should stall, current to the heater coil is interrupted
until the engine is restarted.
When the engine starts, manifold vacuum is applied
to the choke vacuum diaphragm to open the choke valve
slightly. This is called the initial choke valve clearance.
If the engine is accelerated during the warm-up pe-
riod, the corresponding drop in manifold vacuum allows
the thermostatic coil to momentarily close the choke
valve to provide a richer mixture.
CARBURETOR i f ERIAUL
In addition to Model 2100 overhaul procedures, per-
form the following:
Oisasseihlf
(1) Remove attaching screws and remove com-
pensation assembly and gasket from carburetor body.
(2) Remove aneroid-to-chamber screws. Remove
gasket and aneroid from chamber.
gleaning and Inspection
CAUTION: Do not immerse any part of the altitude
compensation assembly in cleaning solvent. Wipe all
parts with clean, lint-free cloths.