Accelerating Pump - Hudson 1953 Jet Mechanical Procedure Manual

FIGURE 1
CLIMATIC CONTROL (CHOKE)
The Climatic Control c1oses the choke
valve when the engine is cold. The Climatic
Control is connected to the exhaust manifold by
a tube (J-Figure 1) which allows exhaust gases
to enter through the opening into the control
housing and warm the thermostatic spring (C)
and decreases the spring tension. A Vacuum
piston (D) is connected to the choke valve and
operates from the vacuum of the intake mani-
fold. The pull of the piston against the thermo-
static spring opens the choke valve (H) as the
engine becomes warm.
FAST IDLE
A cam on the choke valve shaft is brought
against an adjusting screw when the choke is
closed.
The screw is adjusted to hold the throttle
open sufficiently to provide necessary engine
speed (fast idle) during the warm up period.
An unloader (G) is provided in the choke
linkage to open the 'choke valve when the
accelerator pedal is fully depressed. This al-
lows the engine to clear itself of excess fuel if
FUEL SYSTEM & EXHAUST 42
the engine is flooded during the starting period.
As the choke valve opens, the fast idle cam
moves away from the screw allowing the engine to
run at normal idle speed.
ANTI-PERCOLATOR VALVE
When the car stands in extreme ly hot weather
or after a hard run, fuel in the carburetor bowl may
vaporize and set up pressure in the bowl. To pre-
vent this pressure forcing the fuel out the high
speed nozzle (percolating), a saxophone key type
anti-percolator valve vents the carburetor bowl to
the atmosphere when the throttle is closed, reliev-
ing the pressure in the bowl, Figure 2. An anti-
percolator valve that opens too early will allow
excess air to be drawn into the high speed circuit.
If the valve fails to open, it will cause difficult
starting when the engine is hot.
FIGURE 2

ACCELERATING PUMP

The carburetor incorporates a throttle operated
accelerating pump, Figure 3, which discharges
additional fuel into the carburetor