5 HARD START AND NO START DIAGNOSTICS 183
• 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 b etwe en the fuel in le t fitting, strainer,
and fuel pump can cause high-restriction and low
fuel pressure.
• Debris in the fuel regulator valve
• Failed fuel pres s ure regu lator valv e.
• Failed fuel pump
• Failed high-pressure oil pump (can not operate
fuel pump)
Aerated fuel
• Failed seal for inlet fittinginfuelfilter hous ing
• Supply filter or water separator leaking
• Aloosefuellineonthesuctionsideofthefuel
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
•Dirtyfilter 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 fu el 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 regu lat or 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
•Hoseclamp(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
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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