CARBURETOR AND THROTTLE LINKAGE
6E- 45
1
2 3
45
6 7 8
Sectional View Of 19 US Carburetor (both barrels)
1
PIug(transition channels, secondary barrel)
6 Float chamber
2
Carburetor
cover 7 Idle air passage
3 Vent tube
8
Idle air
iet
4Transit’
,n
iet
9 Idle air adjusting screw
5
Transition air
iet
10 Mixture adjusting screw
6E-1
Figure 6E-1 Sectional View of Primary and Secondary Barrels
valve gradually opens and the mixture
become+
leaner. During this process, the abutment lever
changes position on the fast idle cam, further closing
Before starting a cold engine slowly, depress the
ac-
celerator pedal three times before engaging the
starter.
the throttle valve until, the engine is at normal oper-
ating temperature, the choke valve is wide open and
the throttle valve is in slow idle position.
Idle and Part Throttle System
A choke diaphragm is connected to the intermediate
lever of the choke valve spindle through a pull rod.
The vacuum, which develops below the throttle
valve, takes effect on the diaphragm through a
vacuum passage. See Figure
6E-4.
As soon as the
engine starts, this vacuum pulls the choke valve
slightly open; the amount of choke valve opening
depends on the amount of vacuum, which depends
on the engine load. Therefore, with a light engine
load, the choke valve will open slightly; with a heavy
engine load, the valve will close slightly to give a
richer mixture as required for this engine load.
At engine idle grid during low speed (part throttle)
operation, fuel is drawn from the emulsion tube bore,
controlled by the idle jet and mixed with air entering
through idle air bleeds (Figure
6E-1)
and ports in the
throttle body. This mixture is drawn downward to
the three ports near the throttle valve. When the
throttle valve is closed, the mixture is drawn from
the lowest port and mixed with air by-passing the
throttle valve to form the idle mixture.
Turning the idle mixture screw (Figure
6E-1)
inward
results in a leaner mixture, and turning it out results
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