5 HARD START AND NO START DIAGNOSTICS 167
Figure 193 Diagnostic coupling
1. Valve
2. Center section
NOTE: Engines are equipped with a fuel pressure
test valve in the form of either a Shrader valve or a
diagnostic coupling.
2. Check for indications of aerated fuel in the fuel
system. Relieve pressure from the fuel rail using
the fuel pressure test valve.
• As fuel pressure is relieved, a steady stream
of fuel, without air from the fuel pressure test
valve, means that air is not in the fuel system.
• An erratic air/fuel mixture surge suggests that
air is in the fuel system.
Figure 194 Fuel pressure test adapter
NOTE: Itisrecommendedtousethefuelpressure
test adapter to avoid bending the needle in the fuel
pressure test valve.
Figure 195 Fuel test fitting
NOTE: Some engines will have a diagnostic coupling
instead of a Shrader valve. Press end of coupling with
a pocket screwdriver to relieve pressure.
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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