Opel 1900 1973 Service Manual page 336

Carburetor cover
3 Vent tube
valve gradually opens and the
leaner. During this process, the abutment lever
changes position on the fast idle cam, further closing
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.
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.
Sectional View Of 19 US Carburetor (both barrels)
channels, secondary barrel)
Figure 6E-1 Sectional View of Primary and Secondary Barrels
mixture become+
CARBURETOR AND THROTTLE LINKAGE
6 Float chamber
7 Idle a i r passage
8 Idle air iet
9 Idle air adjusting screw
10 Mixture adjusting screw
Before starting a cold engine slowly, depress the ac-
starter.
Idle and Part Throttle
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
idle air
through bleeds
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
System
(Figure 6E-1) ports in the
and