Fuel Injector Diagnosis
Diagnostic Instructions
Circuit/System Description
The control module enables the appropriate fuel injector pulse
for each cylinder. The ignition voltage is supplied directly to the
fuel injectors. The control module controls each fuel injector by
grounding the control circuit via a solid state device called a
driver. A fuel injector coil winding resistance that is too high or
too low will affect the engine driveability. A fuel injector
control circuit DTC may not set, but a misfire may be apparent. The
fuel injector coil windings are affected by temperature. The
resistance of the fuel injector coil windings will increase as the
temperature of the fuel injector increases.
When performing the fuel injector balance test, the scan tool is
first used to energize the fuel pump. The fuel injector tester is
then used to pulse each injector for a precise amount of time,
allowing a measured amount of the fuel to be injected. This causes
a drop in the system fuel pressure that can be recorded and used to
compare each injector.
Diagnostic Aids
| • |
Operating the vehicle over a
wide temperature range may help isolate the fuel injector that is
causing the condition. |
| • |
Perform the fuel injector coil
test within the conditions of the concern from the customer. A fuel
injector condition may only be apparent at a certain temperature,
or under certain conditions. |
Reference Information
Schematic Reference
Engine Controls Schematics
Connector End View Reference
Component Connector End Views
Electrical Information Reference
Special Tools
CH 48027-5 Digital Pressure Gauge
For equivalent regional tools, refer to
Special Tools .
Component Testing
Fuel Injector Coil Static Test
Verify the resistance of each fuel injector with one of the
following methods:
| • |
If the engine coolant
temperature (ECT) sensor is between 10-32°C (50-90°F), the
resistance of each fuel injector should be 11-14 Ω.
|
| ⇒ |
If the injectors measure OK, perform the Fuel
Injector Balance Test and the Fuel Pressure Test. |
| ⇒ |
If not within the specified range, replace the
fuel injector. |
| • |
If the ECT sensor is not
between 10-32°C (50-90°F), measure and record the
resistance of each fuel injector with a DMM. Subtract the lowest
resistance value from the highest resistance value. The difference
between the two should be equal to or less than 3 Ω.
|
| ⇒ |
If the difference is equal to or less than 3
Ω, refer to
Fuel Pressure Measurement for further diagnosis of the fuel
injectors. |
| ⇒ |
If the difference is more than 3 Ω, add all
of the fuel injector resistance values to obtain a total resistance
value. Divide the total resistance value by the number of fuel
injectors to obtain an average resistance value. Subtract the
lowest individual fuel injector resistance value from the average
resistance value. Compute the difference between the highest
individual fuel injector resistance value and the average
resistance value. Replace the fuel injector that displays the
greatest difference above or below the average. |
Fuel Pressure Test
|
Note:
| • |
DO NOT perform
this test if the engine coolant temperature (ECT) is above 94°C
(201°F). Irregular fuel pressure readings may result due to hot
soak fuel boiling. |
| • |
Verify that
adequate fuel is in the fuel tank before proceeding with this
diagnostic. |
| • |
Before proceeding
with this test review the User Manual CH-48027-5 for Safety
Information and Instructions. |
|
| 2. |
Turn ON the ignition, with the
engine OFF. |
|
Note:
| • |
The fuel pump
relay may need to be commanded ON a few times in order to obtain
the highest possible fuel pressure. |
| • |
DO NOT start the
engine. |
|
| 3. |
Command the fuel pump relay ON
with a scan tool. |
| 4. |
Observe the fuel pressure
gauge with the fuel pump relay commanded ON. The fuel pressure
should be 345-414 kPa (50-60 PSI). |
| 5. |
Monitor the fuel pressure
gauge for five minutes. The fuel pressure should not decrease more
than 34 kPa (5 PSI). |
Repair Instructions
Perform the
Diagnostic Repair Verification after completing the diagnostic
procedure.
Fuel Injector Replacement
|
