6 PERFORMANCE DIAGNOSTICS 267
5. Connect Fuel/Oil Test Coupler to test fitting.
6. Drive vehicle and make sure engine operating
temperature reaches 70 °C (158 °F) or higher.
7. Find a long, open stretch of road.
8. When driving conditions are safe, select a suitable
gear, press accelerator pedal fully to the fl oor, and
accelerate to rated speed at 100% load.
9. Memorize gauge reading for fuel inlet restriction.
After parking vehicle, record reading on
Diagnostic Form; do not record reading while
driving.
• If inlet restriction exceeds specification, find
the restriction on the suction side of the fuel
system and correct.
• If inlet restriction is to specification, but
fuel pressure is below sp ecificatio n , test
Operation of Fuel Pump in Test 6 of this
section.
• If fuel pump is operating correctly, replace fuel
regulator valve.
• If inlet restriction and fuel pressure are to
specification, continue wit h performance
diagnostics.
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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