36 1 ENGINE SYSTEMS
NOTE: Early fuel filter assemblies may have item 2 in
the location of item 9. Item 2 is used by the assembly
plants as a fuel fill.
• If item 2 is installed on housin g co v e r assembly, it
canbeusedtomeasureunfiltered fuel pressure.
• If item 2 is installed in item 9 lo cation, it can be
used to measure fuel inlet restriction.
The low-pressure fuel supply pump draws fu el from
the fuel tank through a 150 micron strainer in the fuel
filter assembly.
An optional electric heating element in the fuel filter
housing warms incoming fuel to prevent waxing.
If water is in the fuel, t he filter element repels water
molecules, water collects at the bottom of the element
cavity in the fuel filte r housing, and a Water In Fuel
(WIF) senso r in the element cavity detects water in
the fuel. When enough water accumulates in the
element cavity, the WIF sensor signal changes to the
Electronic Control M odule (ECM). The ECM sends a
message to illuminate the amber water and fuel la mp,
alerting the operator. A fuel drain valve handle on the
housing can be opened to drain contaminants (usually
water) from the fuel filter housing. Another drain valve
in the bottom of the housing drains strainer cavity.
A built-in fuel regulator valve, calibrated to open at
about 414 - 482 kPa (60 - 70 psi), regulates and
relieves e xcessive pre ssure. Durin g idle and light
engine loads, when injector demand is low, most of
the fuel is recycled between the fuel filter housing
and fuel pump. W hen engine demand increases,
engine fuel consumption increases resulting in less
fuel recycling. Under heavy loads fuel flows through
the filter with little or no recycling.
Fuel is conditioned as it flows through a main filter
and stand-pipe. The stand-pipe prevents fuel from
draining from the fuel rail during servicing.
An optional Engine Fuel Pressure (EFP) sensor
detects low pressure caused by high fuel filter
restriction and sends a signal to the ECM. The ECM
illuminates the amber FUEL FILTE R lamp on the
instrume nt panel.
Fuel flows from the fuel filter housing into the fuel rail,
through the fuel rail into six separate passages, one
for each injector.
When the fuel injecto rs ar e activ ated, fuel flows (from
fuel rail) into four in lets in each injector.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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