Outlet (B, Fig. 4-7). These filters are replaceable at
b. General The mechanical-type fuel pump generally is
intervals and contain no sediment bowls. (3) Glass Bowl
the most popular for gasoline engine applications. It
Filter with Replaceable Element (C, Fig. 4-7). The
usually is more than adequate and is much cheaper than
an electric pump. The electric pump is more desirable
sediment bowl must be washed out whenever the
though, for the following reasons.
element is replaced. Some fuel pumps have a glass
bowl-type gas filter built in.
(1) The electric pump will supply fuel to the engine
e. Element Configurations (Fig. 4-8). Filter elements
immediately when the ignition key is turned on. The
are made from ceramic, treated paper, sintered bronze,
engine must be turning with the starter for a mechanical
or metal screen. There is one filter element that differs
pump to operate.
from the others. It consists of a pile of laminated disks
(2) The pump, by design, will operate more efficiently if
that are spaced 0.0003 in. (0.0076 mm) apart. As the
it pushes the fuel rather than pulling it. An electric pump
gasoline passes between the disks, foreign matter is
can be mounted close to the tank, or in the tank, to take
advantage of this characteristic.
4-3. Fuel Pumps.
(3) The electric pump can be mounted away from heat
to reduce the possibility of vapor lock (para4-37).
a. Purpose. The fuel pump delivers gasoline from the
fuel tank to the engine. Early automotive equipment
c. Mechanical, Nonpositive Type (Fig. 4-9).
utilized gravity to feed gasoline to the engine. This Is no
This is currently the most popular configuration of an
longer practical because it limits the location of the fuel
automotive fuel pump. Operation is as follows:
tank to positions that are above the engine.
Figure 4-7. 4-4