system to the high-speed system. The acceleration
system squirts a stream of fuel into the air horn when the
fuel pedal is pressed and the throttle plates swing open.
Without the acceleration system, too much fuel would
rush into the engine, as the throttle quickly opened. The
mixture would become too lean for combustion and the
engine would STALL or HESITATE. The acceleration
system prevents a lean air-fuel mixture from upsetting a
smooth increase in engine speed.
The basic parts of the acceleration system are the
pump linkage, the accelerator pump, the pump check
ball, the pump reservoir, the pump check weight, and
the pump nozzle.
The ACCELERATOR PUMP develops the
pressure to force fuel out of the pump nozzle and into
the air horn. There are two types of accelerator
pumpspiston and diaphragm type (figs. 4-22 and
Figure 4-22.Piston accelerator pump.
Figure 4-23.Diaphragm accelerator pump.