
156 RENR9348-01
Troubleshooting Section
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6-06 Cylinder #6 Injector short
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7-05 Cylinder #7 Injector open circuit
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7-06 Cylinder #
7 Injector short
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8-05 Cylinder #8 Injector open circuit
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8-06 Cylinder #8 Injector short
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9-05 Cylinder
#9 Injector open circuit
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9-06 Cylinder #9 Injector short
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10-05 Cylinder #10 Injector open circuit
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10-06 Cylinde
r #10 Injector short
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11-05 Cylinder #11 Injector open circuit
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11-06 Cylinder #11 Injector short
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12-05 Cylinde
r #12 Injector open circuit
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12-06 Cylinder #12 Injector short
Perform this procedure under conditions that are
identical to the conditions that exist when the problem
occurs. Typic
ally, problems with the injector solenoid
occur when the engine is warmed up and/or when
the engine is under vibration (heavy loads).
These engines have Electronic Unit Injectors (EUI)
that are mechanically actuated and electronically
controlled.
The Engine Control Module (ECM) sends
a high voltage signal to each injector solenoid. The
signal is sent with the proper injection duration and
injection t
iming for the current engine load and
speed. The injector solenoid is mounted on top of
the fuel injector body.
If an open circuit condition is detected in the solenoid
circuit, a diagnostic code is generated. The ECM will
continue to
try to fire the injector. If a short circuit
condition is detected, a diagnostic code is generated.
The ECM will disable the solenoid circuit. The ECM
will perio
dically try to fire the injector. If the short
circuit condition remains, this sequence of events will
be repeated until the problem is corrected.
Note: Refer to Illustration 86. Two injector solenoids
share a supply wire. For this reason, an open
circuit o
r a short circuit in a supply wire could cause
diagnostic codes for two injector solenoids.
When an in
jector is replaced, new injector trim files
must be programmed into the ECM. If the ECM is
replaced, all injector trim files must be programmed
into the n
ew ECM. Refer to Troubleshooting, “Injector
Trim File” for more information.
The Caterpillar Electronic Technician (ET) includes
the following t
ests that aid in troubleshooting the
injector solenoids:
“Cylinder Cut
out Test”
The “Cylinder Cutout Test” is used on an engine
in order to det
ermine the individual cylinder
performance while the engine is running. As one
or more cylinders are cut out during the test, the
“Cylinder Cu
tout Test” uses “Fuel Position” in order
to evaluate the performance of the cylinders that
are cut out. As the different cylinders are cut out, a
comparison o
f the change in “Fuel Position” is used
to identify cylinders that are weak or misfiring. One
reason for a cylinder that is weak or misfiring is an
injector th
at is malfunctioning.
The“CylinderCutoutTest”canbeusedtoisolatea
malfunctio
ning injector in order to avoid replacement
of injectors that are in good condition.
During the
test, when a cylinder is cut out, an
increase in “Fuel Position” will be noticed for the
remaining cylinders. This increase in “Fuel Position”
represent
s an increase in the amount of fuel that
must be delivered by the remaining cylinders in order
to maintain the desired engine speed.
When a weak cylinder (malfunctioning injector) is cut
out, the increase in “Fuel Position” will not be as large
as the inc
rease for a cylinder that has an acceptable
level of performance.
Note: Pri
or to running the “Cylinder Cutout Test”, all
active diagnostic codes must be repaired.
“Injecto
r Solenoid Test”
Use the “Injector Solenoid Test” to diagnose an open
circuit o
r a short circuit in the wiring for the injector
solenoids. With the engine stopped, the “Injector
Solenoid Test” will briefly activate each injector
solenoi
d. An audible click can be heard as each
solenoid is activated. After performing the test, Cat
ET will indicate the status of the solenoid as “OK”,
“Open”,
or “Short”.