•
Restriction 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 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
Read all safety instructions in the "Safety Information" section of this manual before doing any procedures.
5 HARD START AND NO START DIAGNOSTICS
Follow all warnings, cautions, and notes.
© August 2008 Navistar, Inc.
•
Restriction from the low-pressure 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 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.
High fuel pressure (pulsating fuel pressure)
•
Debris in the fuel regulator valve
•
Inoperative fuel pressure regulator valve.
•
Combustion gases leaking into fuel system
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
•
Spare fuel line (filter housing to fuel supply pump)
•
Clear plastic line
•
Hose clamp (2)
Procedure
WARNING: To avoid serious personal injury,
possible death, or damage to the engine or
vehicle, read all safety instructions in the "Safety
Information" section of this manual.
EGES-270-1
183