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C. ACCELERATING PUMP SYSTEM - The
accelerating pump is located in the bottom of the
primary fuel bowl. The pump begins to function
when the pump operating lever is actuated by
throttle movement. When the throttle is opened, the
pump linkage, actuated by a cam on the primary
throttle shaft, forces the pump diaphragm up. As
the diaphragm moves up, the pressure forces the
pump inlet check ball on its seat preventing fuel
from flowing back into the float chamber. The fuel
flows from the short passage in the fuel bowl into
the long diagonal passage in the primary metering
body. The fuel passes into the main body and then
in the pump discharge chamber. The pressure of
the fuel causes the discharge ball check and weight
or needle valve on some models, to raise and
allows the fuel to travel into the pump discharge
nozzle which directs the fuel down into the venturi.
As the throttle is moved toward the closed position,
the linkage returns to its original position and the
diaphragm spring forces the diaphragm down. As
the diaphragm returns to its original position, the
pump inlet check ball is moved off its seat and the
diaphragm chamber is filled with fuel from the
float bowl. |
