Figure 4-37. Choke Valve Operation.
(1) Electricity (Fig. 4-40). A large portion of the
(3) Intake Manifold Crossover (Fig. 4-42). One
vehicles currently produced use an electric coil to heat
of the most popular methods of providing choke heat,
the thermostatic coil. The heating coil is switched on with
until recent years, is to utilize exhaust heat. The most
the ignition switch. Some systems employ a control unit
popular way of doing this Is to mount the choke
that prevents power from reaching the electric coil until
mechanism containing the thermostatic coil in a molded
the engine compartment reaches a desired temperature.
well on the intake manifold over the crossover passage.
The choke mechanism then operates the choke valve
(2) Engine Coolant (Fig. 4-41). Another method
of heating the thermostatic coil is to circulate engine
(4) Exhaust Manifold (Fig. 4-43). This system
coolant through a passage in the thermostat housing.
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
Figure 4-38. Manual Choke System.