244 6 PERFORMANCE DIAGNOSTICS
11. Injector Disable Test
Figure 315
Purpose
To determine the cause of rough engine idle
The Injector Disable Tests can only be done with the
EST; MasterDiagnostics® software is required.
The Injector Disable Tests allows the t echnician to
shut-off injectors to determine if a specific cylinder is
contributing to engine performance. Injectors c an be
shut off one at a time, alte rnative c ylinders at a time
or alt ern at ive cylinders plus one.
Alternate cylinders are every other cylinder in firing
order.
Firing order: 1–5–3–6–2–4
When all c ylinders are active, the contribution of
each cylinder is 17% of its overall effect to maintain
governed speed. When three cylinders are shut off,
contribution of each remaining cylinder is 33% of
its overall effect to maintain governed speed. The
technician should monitor fuel rate and engine load.
NOTE: The Relative Compression Test 12 should
be done after doing the Injector Disable Test 11
to distinguish between an injector or mechanical
problem.
Tools
• EST with MasterDiagnostics® software
• EZ-Tech® interface cable
NOTE: Before doing the Automatic Test or Manual
Test for injector disable, make sure Tests 1 through
10 w ere completed and the following condition s are
maintained:
• Make sure accessories are turne d off. (Exa m p le
– engine fan and air conditioning) Items cycled
during this test cou ld c o rru pt the test results.
• Maintain engine idle.
• Keep EOT within a 2 °C (5 °F) range from the
beginning to the end of the test. EOT affects
injection timing ; too much of a chan g e in EOT
temperature could corrupt the test results.
Automatic Test – Auto Run
The Automatic Test is best done when comparing
cylinder to cylinder test data.
NOTE: If MasterDiagnostics® software does not have
the Automatic Test (auto run feature), Injector Disable
– Manual Test in Section 3 for procedure to compare
cylinder to cylinder.
NOTE: Do KOER Standard test before doing this test.
WARNING: To avoid serious personal injur
y,
possible death or damage to the engine or
vehicle
– comply with the following:
When running the engine in the service ba
y, make
sure the parking brake i s set, the trans
mission is
in neutra l, and the wheels are block
ed.
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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