PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 1/TASK 2
chamber to cushion the pulsating action inherent to the diaphragm-type pump.
(10) An oil seal is provided to keep crankcase oil from entering the
lower chamber and leaking from the venthole.
d. Mechanical, Positive Type.
The positive-type mechanical pump
operates in the same manner as the nonpositive-type. The difference is that
the diaphragm pull rod is solidly linked to the rocker arm.
therefore, will not regulate fuel line pressure. When this type of pump is
used, a separate fuel pressure regulation device must be employed which will
bypass excess fuel back to the fuel tank.
e. Double Action Fuel Pump (figure 5).
Vehicles that use vacuum-
operated windshield wipers will often use a supply pump that is built into
the fuel pump.
The pump serves to operate the windshield wipers during
periods of high engine load when the
DOUBLE ACTION PUMP.