126 4 ENGINE SYMPTOMS DIAGNOSTICS
Figure 147 Fuel/Oil Pressure Test C oupler
NOTE: If the engine is equipped with a diagnostic
coupling, adapt the Fuel/Oil Pressure Test Coupler to
the Fuel Pressure Gauge.
Figure 148 Fuel Pressure Gauge to fuel pressure
test adapter
5. Connect a fuel pressure gauge with shut-off valve
and clear 3/8” diameter hose to test valve.
6. Route the clear hose into a drain pan.
7. Open the gauge setup shut-off valve
8. Shine the black light at the fuel pressure gauge
clear line. The dyed fuel will have a yellow-green
fluorescent glow.
9. Using the priming pump, purge the fuel until the
dyed fuel begins to flow fro m the pre ssure gauge
clear hose.
10. Close the shut-off valve.
11. Remove the valve cover following th e procedure
in the Engine Service Manual.
12. Start and run the engin e at low idle for 3 to 5
minutes.
Figure 149 High-pressure oil rail with
injector
13. While the engine is running, use the bl
ack light to
inspect for yellow-green streams of
dye running
between the valve spring s eats at ea
ch injector.
A small mirror can aid in hard to reac
hareas.
Inspection should take no longer
than 5 minutes.
Because disbursement of dye in t
he fuel, the
amount of dye seen does not indi
cate severity of
failure, only that a failure ex
ists.
NOTE: If no dye or leak is found a
fter running
engine, verify there is fue
l dilution issue by oil
analysis or observing an oi
l level increase.
• If a leak is found, turn off t
he engine. Do steps
14 through 17.
• If a leak is not found, turn o
ff the engine.
Continue with step 18.
14. Remove the high-pressur
e oil rail following the
procedure in the Engine
Service Manual.
15. Inspect remaining injec
tors for leaks. Failed
injectors will have a so
lid yellow-green color
around the intensifier
body area (weep hole).
16. Relieve the pressure
in the fuel system to avoid
further contaminati
on of oil.
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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