Fuel Injector Diagnosis (LC8FHZ)

Fuel Injector Diagnosis (LC8\FHZ)

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 provide an overview of each diagnostic category.

Circuit/System Description

The engine control module (ECM) enables the appropriate fuel injector pulse for each cylinder. The ignition voltage is supplied directly to the fuel injectors. The ECM 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.

Diagnostic Aids

* Monitoring the misfire current counters, or misfire graph, may help to isolate the fuel injector that is causing the condition.

* 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 customer's concern. 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 1-2 Shift Solenoid (SS) Valve (M30)

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

DTC Type Reference

Powertrain Diagnostic Trouble Code (DTC) Type Definitions Powertrain Diagnostic Trouble Code (DTC) Type Definitions

Scan Tool Reference

Control Module References Control Module References for scan tool information

Special Tools

CH-48027 Digital Pressure Gauge

Component Testing

Fuel Injector Coil 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 10-14 ohms.

• If the injectors measure OK, perform the Fuel Injector Balance Test - 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 lowest value and the highest value should be equal to or less than 3 ohms.

• If the difference is equal to or less than 3 ohms, refer to Fuel Injector Balance Test - Fuel Pressure Test 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.

Injector Performance 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 CH-48027. Refer to Fuel Pressure Gauge Installation and Removal Fuel Pressure Gauge Installation and Removal.

2. Ignition ON, with the engine OFF.

Note:
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 commanded ON. The fuel pressure should be 620-758 kPa (90- 110 psi).

• If the fuel pressure is not 620-758 kPa (90- 110 psi), refer to Fuel System Diagnosis (Without FPCM) Fuel System Diagnosis (Without FPCM)Fuel System Diagnosis (LC8\K07\UFP) Fuel System Diagnosis (LC8K07UFP)Fuel System Diagnosis (LC8\FHZ) Fuel System Diagnosis (LC8FHZ)Fuel System Diagnosis (FPCM) Fuel System Diagnosis (FPCM).

5. Operate the vehicle under the conditions of the customers concern. Verify the fuel pressure is between 620-758 kPa (90- 110 psi).

• If the fuel pressure is not 620-758 kPa (90- 110 psi), refer to Fuel System Diagnosis (Without FPCM) Fuel System Diagnosis (Without FPCM)Fuel System Diagnosis (LC8\K07\UFP) Fuel System Diagnosis (LC8K07UFP)Fuel System Diagnosis (LC8\FHZ) Fuel System Diagnosis (LC8FHZ)Fuel System Diagnosis (FPCM) Fuel System Diagnosis (FPCM).

6. Inspect the following items

* Inspect the fuel system for items that could alter the amount of fuel delivery to the engine.

- Inspect for a leaking injector or fuel rail

- Inspect for a restricted fuel filter

- Inspect for a kinked, bent, or restricted fuel supply line

- Verify the Manual shut off valves are open completely

- Verify the 1/4 turn shut off valve is open completely

* Inspect the engine mechanical for items that could alter the air flow into the combustion chamber.

* Monitor the misfire current counters, or misfire graph, to isolate the fuel injector or cylinder that is causing the condition.

- Perform a cylinder balance test

- Perform a cylinder compression test

• If misfire counter or misfire graph indicates a suspect cylinder and all other checks do not indicate a concern, replace the fuel injector of the suspect cylinder. Refer to Fuel Injector Replacement Removal and Replacement.

Repair Instructions

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

* Compressed Natural Gas High Pressure Regulator Filter Replacement Compressed Natural Gas High Pressure Regulator Filter Replacement

* Compressed Natural Gas High Pressure Regulator Replacement Compressed Natural Gas High Pressure Regulator Replacement

* Fuel Injector Replacement Removal and Replacement