226
•
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 regulator valve
•
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
•
A loose fuel line on the suction side of the fuel
system can ingest air into the system 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
•
Dirty filter element
•
Debris or rust in fuel strainer
•
Restriction from the low-pressure fuel filter
housing inlet to the fuel tank can cause
high-restriction and low fuel pressure.
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
6 PERFORMANCE DIAGNOSTICS
•
•
•
•
•
•
High fuel pressure (pulsating fuel pressure)
•
•
•
Checking for Aerated Fuel using Spare Fuel Line
NOTE: This is an alternative test. Do this procedure,
only if Fuel Pressure Gauge with shut-off valve is not
available.
Tools
•
•
•
Procedure
possible death, or damage to the engine or
vehicle, read all safety instructions in the "Safety
Information" section of this manual.
EGES-270-1
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
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 regulator valve
Inoperative fuel pressure regulator valve.
Combustion gases leaking into fuel system
Spare fuel line (filter housing to fuel supply pump)
Clear plastic line
Hose clamp (2)
WARNING: To avoid serious personal injury,