264 6 PERFORMANCE DIAGNOSTICS
Fuel Possible Causes
No fuel
• Low fuel level in fuel tank
• Debris in tank can cause high-restriction and low
fuel pressure.
• Inline fuel valve (if equipped) could be shut-off
• Failed seals or fuel lines between fuel tanks
• Ice in fuel lines
• Inoperative fuel tank transfer pump
• Fuel tank pickup tube cracked
Low fuel pressure
•Dirtyfilter element
• Debris or rust in fuel strainer
• Restric tion from the fuel tank to the fuel filter
housing inlet can cause high-restriction and low
fuel pressure.
• Plugged supplemental filters or water separators
can cause high-restriction and low fuel pressure.
• Debris in tank can cause high-restriction and low
fuel pressure.
• A kinked or bent fuel supply line or a blocked
pickup tube can cause high-restriction and low
fuel pressure.
• Waxed or jelled fuel in the fuel filter will cause
high-restriction and low fuel pressure. (Usually
Grade 2-D)
• Ice in fuel lines.
• A restriction between the fuel inlet fitting, strainer,
and fuel pump can cause high-restriction and
low fuel pressure.
• Debris in the fuel reg ulator v alve
• Failed fuel pressure regulator valve.
• Failed fuel pump
• Failed high-pressure oil pump (can not operate
fuel pump)
Aerated fuel
• Failed seal for inlet fitting in fuel filter housing
• Supply filter or water separator leaking
• Aloosefuellineonthesuctionsideofthefuel
system can ingest air into the s ystem and cause
low fuel pressure (most noticeable under load).
• Strainer drain valve loose or damaged
• Strainer bowl warped or damaged
• Missing O-ring from strainer bowl
• Damaged seals on steel inlet tube to fuel pump
• Primer pump seals damaged
Fuel restriction
•Dirtyfilter element
• Debris or rust in fuel strainer
• Restric tion from the fuel filter housing inlet to
the fuel tank can cause high-restriction and low
fuel pressure.
• Plugged supplemental filters or water separators
can cause high-restriction and low fuel pressure.
• Debris in tank can cause high-restriction and low
fuel pressure.
• A kinked or bent fuel supply line o r a blocked
pickup tube can cause high-restriction and low
fuel pressure.
• Waxed or jelled fuel in the fuel filter will cause
high-restriction and low fuel pressure. (Usually
Grade 2-D)
• Ice in fuel lines.
• A restriction between the fuel inlet fitting, strainer,
and fuel pump can cause high-restriction and
low fuel pressure.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any proced ures.
Follow all warnings, cautions, and notes.
©August 2008 Navistar, Inc.
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