PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 2
(d) Exhaust Manifold (figure 27). This system has the choke
mechanism mounted on the carburetor in a sealed housing. The choke housing
is connected to a tube that runs through the exhaust manifold. This tube
supplies heat to the choke mechanism. The choke housing also is connected
internally to a manifold vacuum source. As the engine runs, the manifold
vacuum draws air through the heat tube and the choke housing. The heat tube
passes right through the exhaust manifold so that, as it takes in fresh air
via the choke stove, it will pick up heat from the exhaust without sending
any actual exhaust fumes to the choke mechanism. Heating of the fresh air
entering the heat tube occurs in the choke stove.
FIGURE 27. EXHAUST HEATTUBE TYPE CHOKE.
(6) Regulating Choke Valve Opening. As with the manual choke system,
a device must be incorporated that will open the choke a measured amount
against the force of the thermostatic coil. The manifold vacuum usually is
used to operate this choking device.
(a) Choke Piston. The choke piston can be integral to the
carburetor, as can the passage that supplies vacuum to it. The vacuum