PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 2
(1) Hot Idle Compensator (figure 35). The hot idle compensator is a
thermostatically controlled valve that helps to prevent engine stalling when
idling in very hot weather. Long periods of engine idle cause an excessive
amount of vaporization of gasoline in the float bowl. These vapors will
find their way into the carburetor throat and cause an overly rich mixture.
The hot idle compensator consists of a bimetallic strip of metal which
operates a valve that controls an air passage ending under the throttle
valve. The bimetallic strip, which consists of two pieces of dissimilar
metal with different expansion rates, will curl upwards as the temperature
increases, opening the valve. This will, in turn, admit air under the
throttle valve compensating for the overly rich mixture.
FIGURE 35. HOT IDLE COMPENSATOR.
(2) Throttle Return Dashpot (figure 36 on the following page). The
throttle return dashpot acts as a damper to keep the throttle from closing
too quickly when the accelerator pedal is suddenly released. This is
important to prevent stalling on cars equipped with automatic transmissions.
The throttle lever contacts the dashpot rod just before the throttle valves
close. This will, in turn, push in on the diaphragm. The diaphragm slows
the closing of the throttle because it must exhaust the air from the chamber
through a tiny venthole. When