Fuel Injector Diagnosis

Fuel Injector Diagnosis

Diagnostic Instructions

* Perform the Diagnostic System Check - Vehicle Diagnostic System Check - Vehicle prior to using this diagnostic procedure.

* Review Strategy Based Diagnosis Strategy Based Diagnosis for an overview of the diagnostic approach.

* Diagnostic Procedure Instructions Diagnostic Procedure Instructions provides an overview of each diagnostic category.

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 [1][2]Electrical Diagrams

Connector End View Reference

Component Connector End Views Fuel Pump and Level Sensor Assembly

Electrical Information Reference

* Circuit Testing Circuit Testing

* Connector Repairs Connector Repairs

* Testing for Intermittent Conditions and Poor Connections Testing for Intermittent Conditions and Poor Connections

* Wiring Repairs Wiring Repairs

Special Tools

CH 48027-5 - Digital Pressure Gauge

For equivalent regional tools, refer to Special Tools Tools and Equipment.

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 ohms.

• 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 ohms.

• If the difference is equal to or less than 3 ohms, refer to Fuel Pressure Measurement Fuel Pressure Measurement for further diagnosis of the fuel injectors.

• If the difference is more than 3 ohms, 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.

1. Install a fuel pressure gauge.

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).

• If the fuel pressure is not 345-414 kPa (50-60 PSI), refer to Fuel System Diagnosis Fuel System Diagnosis.

5. Monitor the fuel pressure gauge for five minutes. The fuel pressure should not decrease more than 34 kPa (5 PSI).

• If the fuel pressure decreases more than 34 kPa (5 PSI), refer to Fuel System Diagnosis Fuel System Diagnosis.

Repair Instructions

Perform the Diagnostic Repair Verification Verification Tests after completing the diagnostic procedure.

Fuel Injector Replacement Service and Repair