PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 2
manifold vacuum is low. The pump operates from a rocker arm and is a
nonpositivetype diaphragm pump. At times when the manifold vacuum alone is
sufficient to operate the windshield wipers, the diaphragm will be held up
against the diaphragm spring by atmospheric pressure, rendering the pump
inoperative.
f. Electric, BellowsType (figure 6). The bellowstype electric fuel
pump works in the same manner as the nonpositivetype mechanical pump. The
difference is that it is driven by an electric solenoid rather than a
mechanical camshaft. Operation is as follows:
(1) As electric current is fed to the pump, the electromagnetic coil
pulls the armature down, expanding the bellows.
(2) The expansion of the bellows causes fuel to be drawn in through
the inlet valve.
FIGURE 6. BELLOWSTYPE ELECTRIC FUEL PUMP.
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