108 4 ENGINE SYMPTOMS DIAGNOSTICS
Figure 122 Fuel filter housing inlet
1. Disconnect the supply line from the fuel filter
housing.
2. Make a test fuel line.
• Usea90°fuellinemalefitting and install a
clear plastic line that is long enough to reach
an alternative fuel source.
NOTE: The mechanic is expected to keep the fuel
test line for future diagnostics. Expense the fuel
test line as an e ssential t ool and keep it w ith other
diagnostic tools. Warranty will not cover the cost
of the fuel test line.
3. Connect the alternate fuel source to the fuel filter
housing inlet.
WARNING: To avoid serious personal
injury, possible death, or damage to the
engine or vehicle – comply with the following:
When routing test line, do not crimp the line,
run the line too close to moving parts, or let
the line touch hot engine surfaces.
4. Start or crank the engine for 20 seconds. Measure
fuel pressure with the shut-off valve closed. Open
the s hut-off valve to check for aeration.
NOTE: Breaking any fuel system joint will induce
air into the fuel system. The air should pass in a
short period of time . As fuel pre ssure is relieve, a
steady stream of fuel without air bubbles indicates
the fuel is not aerated.
NOTE: If a fuel pressure gauge with shut-off valve
and clear 3/8” diameter hose is not available, refer
to the alternative test “Checking for Aerated Fuel
using Spare Fuel Line.”
• If the fuel pressure is in specification and the
fuel is not aerated, repair the leak between the
fuel filter housing and the fuel tank.
• If the fuel is aerated, repair or replace the fuel
filter housing.
Combustion Leaks to Fuel
1. Remove the valve cover following the procedure
in the Engine Service Manual.
2. Check all injector hold-down clamps for correct
torque.
3. Remove any loose injectors. Inspect and clean
following the pro ce dure in the Engine Service
Manual. Replace injector O-rings and install
injectors following the procedure in the Engine
Service Manual.
4. Test for fuel aeration to validate the repair. Go
to “Aerated Fuel Inspection” (page 105) in this
section.
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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