Main Metering Circuit; Power Enrichment Circuit; Model 2Se Carburetor—Idle Circuit; Model 2Se Carburetor—Main Metering Circuit - Jeep J-10 Series 1982 Technical & Service Manual

1J-14 FUEL SYSTEMS
IDLE TUBE
MAIN
METERING JET
IDLE DISCHARGE'
HOLE
IDLE CROSSOVER
PASSAGE
TOP IDLE
AIR BLEED
DLE
CHANNEL
RESTRICTION
LOWER IDLE
AIR BLEED
THROTTLE
VALVE
(OFF IDLE
POSITION)
OFF IDLE
IDLE PLUG
MIXTURE SCREW
90651
Fig. U-22 Model 2SE Carburetor—Idle Circuit
A hot idle compensator assembly (when used) is lo
cated in the air horn casting. The opening and closing of
the hot idle compensator valve is controlled by a bime
tallic strip that is calibrated for a specific temperature.
When the valve opens, additional air is allowed to by
pass the throttle valves and enter the intake manifold to
prevent rough idle during periods of hot engine
operation.
The idle mixture screw is recessed in the throttle body
casting and sealed with a hardened steel plug to dis
courage indiscriminate tampering with the factory ad
justed mixture setting, which could cause excessive
undesirable exhaust emissions. The plug must not be
removed, nor the idle mixture screw readjusted, unless
required because of major carburetor overhaul or
throttle body replacement. Adjustment requires special
service procedures.
Main Metering Circuit
At partial throttle and cruising rpm, increased air
flow creates a low pressure area in the venturi. Because
air above the fuel level in the bowl is at normal pressure,
fuel flows to the lower pressure area created by the
venturi and amplified by the booster venturi.
The fuel flow moves through the main jets to the main
well. Air enters through the main well air bleeds. The
resulting mixture of fuel and air is lighter than raw fuel,
responds more quickly to changes in venturi vacuum,
and is more readily vaporized when discharged into the
venturi (fig. 1J-23).
Power Enrichment Circuit
During heavy load or high speed operation the air/
fuel ratio must be enriched to provide the necessary
increase in engine power.
METERING ROD
HANGER
PLUG
PART
THROTTLE
CALIBRATION SCREW
TOP MAIN WELL
AIR BLEED
MAIN
DISCHARGE
NOZZLE
BOOSTER
VENTURI
MAIN VENTURI
POWER PISTON
POWER
PISTON
SPRING
THROTTLE
VALVE
VACUUM CHANNEL
(TO POWER PISTON)
90652
Fig. U-23 Model 2SE Carburetor—Main Metering Circuit
Power enrichment is accomplished by means of a cali
brated metering rod yoked to a single manifold vacuum
actuated piston (fig. 1J-24).
The metering rod piston rests on a calibrated spring
that functions to maintain the piston at the top of its
cylinder. This allows only the smallest diameter of the
tapered metering rods to extend into the main metering
jets and permits maximum fuel flow through the jets to
the main well cavities.
At idle, partial throttle or cruise conditions, when
manifold vacuum is high, the piston is forced down into
the vacuum cylinder against the calibrated spring ten
sion and the larger diameters of the metering rods ex
tend into the main metering jets. This restricts the fuel
flow to the main well cavities. An additional control is
provided by the rod lifter on the accelerator pump rod.
This establishes a direct relationship between the meter
ing rod position and the throttle valve opening.
ADJUSTING
SCREW
METERING
ROD
HANGER
SECONDARY
AIR
VALVE (OPEN
SECONDARY
METERING ROD
SECONDARY
THROTTLE
VALVE
SECONDARY
METERING
JET
SECONDARY
AIR BLEED
PRIMARY
METERING JET
MAIN (PRIMARY)
METERING ROD
POWER
PISTON
(UP)
POWER PISTON
SPRING
VACUUM
CHANNEL
(TO POWER
PISTON)
FUEL WELL
PRIMARY 90653
Fig. U-24 Model 2SE Carburetor—Power Enrichment Circuit