PRINCIPLES GASOLINE/DIESEL FUEL SYSTEMS - OD1620 - LESSON 2/TASK 2
c. Types. Diesel fuel oil filters are referred to as fullflow
filters, because all the fuel must pass through them before reaching the
injection pumps. A diesel fuel filter usually incorporates an air valve to
release any air that might accumulate in the filter during operation.
(1) Primary Filters (figure 64). Metal filters are used as primary
filters because the fine particles that will pass through them are not
injurious to the supply pump. The filter element is usually of the metal
disk type. Solids larger than 0.005 in. remain outside the metal disks,
while larger foreign matter and the majority of the water settles to the
bottom of the bowl. From here, the foreign matter can be removed through a
drainplug. A ball relief valve in the filter cover enables the oil to
bypass the filter element if the disks become clogged.
FIGURE 64. PRIMARY FUEL FILTER.
(2) Secondary Filters (figure 65 on the following page). Fabric
filters, because of their greater filtering qualities, are most commonly
used
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