PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 2
FIGURE 20. DIAPHRAGM ACCELERATOR PUMP.
manifold rather than vaporizing. By supplying a richer mixture (8:1 to
9:1), there will be enough vapor to assure complete combustion. The
carburetor is fitted with a choke system to provide this richer mixture.
The choke system provides a very rich mixture to start the cold engine. It
then gradually makes the mixture less rich as the engine reaches operating
(2) Operation (figure 21 on the following page). The choke system
consists of a flat plate that restricts the throat above the venturi, but is
located below the balance tube so that it has no affect on the pressure in
the float bowl. This plate is called a choke valve, and, like the throttle
valve, is mounted on a shaft to tilt it opened or closed.