246 6 PERFORMANCE DIAGNOSTICS
Figure 319 I6 Injector Disable Test Results
(Auto Run – Gra p h View)
During Auto Run, injectors are shut off one at a time (1
through 6 in numerical sequence). Baseline data and
results for each cylinder is displayed in the window
(Text View) for I6 Injector Disable Test Results. Test
data for each injector can also be viewed by selecting
the (Graph View).
5. Record data from window (Text View) on
Diagnostic Form.
• If deviation values for average fuel rate and
average engine load are less than the cut
off values for fuel rate and engine load,
the injector is suspect for weak cylinder
contribution.
• If only one deviation value is less than a cut
off value, do not suspect that cylinder.
• If a suspect cylinder(s) is identified, do Test 12
Relative Compression to distinguish between
an injector or mechanical problem.
• If Test 12 shows that cylinders are
mechanically sound, but the Injector Disable
Test shows that one or more cylinders are
bad, continue with step 6.
6. Remove valve cover following procedure in
Engine Service Manual.
7. Replace faulty injector(s) following procedures in
the Engine Service Manual.
8. Test drive vehicle for 20 miles to purge air from
ICP system and fuel supply system. Check for
rough idle.
9. If rough idle continues, do the I njector Disable Te st
again.
Possible Caus es
• Failed connection from wiring h arne ss to injector
solenoid
• Open or shorted wiring harness to injector
solenoid
• Failed solenoid on fuel injector
• Scuffed o r damaged injector
• Failed IDM
• Failed ECM
Manual Test
The Manual Test is best done when diagnosing each
cylinder for cold misfire, considering EOT changes.
The EOT indicator w ill change from red to green when
engine temperature reaches 70 °C (158 °F) or higher.
• If the EOT indicator is red, erroneous
comparison s are likely from cylinder to cylinder.
However, when diagnosing a cold misfire, a
technician can listen to tone changes from
cylinder-to-cylinder.
• When the EOT indicator is green and the engine
temperature is 70 °C (158 °F) or higher, fuel rate
and timing are more stable, making comparisons
from cylinder to cylinder more accurate. Overall
engine operation is more stable.
Shut off one injector at a time and listen for changes
in exhaust tone.
NOTE: If any injectors are removed and reinstalled
or replaced, test drive vehicle for 20 miles before
checking for misfire or rough idle.
WARNING: To avoid serious persona
linjury,
possible death or damage to the en
gine or vehicle
– comply with the following:
When running the engine in the ser
vice bay, make
suretheparkingbrakeisset,th
e transmission is
in neutra l, and the wheels are bl
ocked.
EGES-270-1
Read all safety instructions in the "Safety Information" section of this manual before doing any proced ures.
Follow all warnings, cautions, and notes.
©August 2008 Navistar, Inc.
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