Fuel System Diagnosis (LC8K07UFP)

Fuel System Diagnosis (LC8\K07\UFP)

Diagnostic Instructions

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

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

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

Circuit/System Description

The Liquid Propane Control Module supplies battery voltage and ground to the Liquid Propane Delivery Module. The LPDM consists of a fuel supply solenoid valve, purge solenoid valve, and a liquid propane fuel pump relay.

Reference Information

Description and Operation

Fuel System Description (LC8\K07\UFP) Fuel System Description (LC8K07UFP)Fuel System Description (LC8\FHZ) Fuel System Description (LC8FHZ)Fuel System Description (Without LC8) Fuel System Description (Without LC8)

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 Circuit Testing

* Connector Repairs Connector Repairs Connector Repairs

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

* Wiring Repairs Wiring Repairs Wiring Repairs

Scan Tool Reference

Control Module References Control Module References

Special Tools

Pressure Gauge

Circuit/System Verification

Note:

* Repair all fuel system related DTCs before performing this diagnostic, unless instructed here from a DTC diagnostic.

* Inspect the fuel system for damage or external leaks before proceeding.

* Verify that adequate fuel is in the fuel tanks before proceeding.

1. Ignition OFF, all accessories OFF, install a 0-300 psi fuel pressure gauge at the liquid propane delivery module.

2. Ignition ON, command the fuel pump relay ON and OFF with a scan tool several times. Verify there is an audible click from the fuel control solenoids and the in tank fuel pump is turning ON and OFF.

• If NO audible click noise or the fuel pump is not running when commanded ON

Refer to the Liquid Propane Control Module Test

• If an audible click and the fuel pump runs when commanded ON

3. Ignition ON, command the fuel pump relay ON with a scan tool. Verify the fuel pressure is greater than 100 psi

• If less than 100 psi

Refer to the Fuel Supply Solenoid Test

• If greater than 100 psi

4. Ignition ON, disconnect the harness connector at the liquid propane fuel pump relay.

5. Ignition ON, command the fuel pump relay ON with a scan tool. Record the fuel pressure gauge reading. The gauge will display the current tank pressure.

6. Ignition OFF.

7. Purge 50 psi from the fuel system, refer to liquid propane evacuation

Note:
Pressure reading may increase slightly with changes in ambient temperature.

8. Verify the fuel pressure is 50 psi less than the original value.

• If the fuel system pressure does not decrease

Refer to the Liquid Propane Delivery Module Test.

• If the fuel system pressure decreases by 50 psi

9. Install the liquid propane fuel pump relay harness connector

10. Disconnect the purge solenoid control wire from the in-line connector terminal 3 at the liquid propane delivery module.

11. Ignition ON, command the fuel pump relay ON with a scan tool several times. Verify the fuel pressure is 35-50 psi greater than the tank pressure. This pressure value is the fuel system pressure.

• If the fuel pressure does not increase by 35-50 psi

Refer to Primary Fuel Pump Test

• If the fuel pressure increases by greater than 50 psi

Test or replace the purge sollenoid

• If the fuel pressure increased by 35-50 psi

12. Install the purge solenoid control wire into the in-line harness connector at the liquid propane delivery module.

Note:
The purge valve is only energized during the first 5 seconds of ignition ON.

13. Ignition ON, within 5 seconds verify the fuel pressure is 5-15 psi less than the recorded fuel system pressure.

• If the fuel pressure does not decrease by 5-15 psi

Refer to Purge Solenoid Test

• If the fuel pressure decreases greater than 15 psi

Test or replace the purge solenoid.

• If the fuel pressure decreases 5-15 psi

14. All OK

Liquid Propane Control Module Test

1. Ignition OFF, disconnect the X1 harness connector at the liquid propane control module.

2. Connect a test lamp between the fuel pump signal circuit J2 and ground.

3. Ignition ON, command the fuel pump relay ON and OFF with a scan tool, verify the test lamp turns ON and OFF with each command.

• If the test lamp is always OFF or always ON

Refer to Fuel Pump Electrical Circuit Diagnosis (FPCM) Fuel Pump Electrical Circuit Diagnosis (FPCM)Fuel Pump Electrical Circuit Diagnosis (LC8\K07\UFP) Fuel Pump Electrical Circuit Diagnosis (LC8K07UFP)Fuel Pump Electrical Circuit Diagnosis (LC8\FHZ) Fuel Pump Electrical Circuit Diagnosis (LC8FHZ)Fuel Pump Electrical Circuit Diagnosis (Without FPCM) Fuel Pump Electrical Circuit Diagnosis (Without FPCM)

• If the test lamp turns ON and OFF with each command

4. Test for 10 ohms or less between the liquid propane control module ground circuit K2 and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

5. Connect a test lamp between the liquid propane control module voltage supply circuit H1 and ground.

6. Verify the test lamp illuminates

• If the test lamp does not illuminate

Note:
Verify the in-line fuse is not open

1. Connect a test lamp between the voltage supply circuit at the in-line fuse holder and ground.

2. Verify the test lamp illuminates.

• If the test lamp does not illuminate, repair the open/high resistance in the voltage supply circuit between the fuse holder and battery.

• If the test lamp illuminates, repair the open/high resistance in the voltage supply circuit between the fuse holder and the liquid propane control module.

• If the fuse is opened, test the voltage supply circuit and the following components for a short to ground

* Liquid Propane Control Module

* Primary Fuel Pump

* Secondary Fuel Pump

* Scavenge Pump

• If the test lamp illuminates

7. Ignition OFF, connect the X1 harness connector at the liquid propane control module.

8. Disconnect the in-line harness connector at the liquid propane delivery module.

9. Test for less than 10 ohms between the harness side of the in-line connector liquid propane delivery module ground circuit terminal 4 and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

10. Connect a test lamp between liquid propane delivery module ground circuit terminal 4 and the supply valve voltage supply circuit terminal 2.

11. Ignition OFF, verify the test lamp does not illuminate.

• If the test lamp illuminates

Refer to Fuel Supply Solenoid Testing

• If the test lamp turn does not illuminate

12. Ignition ON, verify the test lamp illuminates.

• If the test lamp does not illuminate

Refer to Fuel Supply Solenoid Testing

• If the test lamp illuminates

13. Ignition OFF, Connect the in-line harness connector to the liquid propane delivery module.

14. Ignition ON, verify the fuel supply solenoid operates.

• If the fuel supply solenoid does not operate

Test or replace the fuel supply solenoid.

• If the fuel supply solenoid operates

15. Ignition OFF, disconnect the in-line harness connector at the liquid propane delivery module.

16. Connect a test lamp between liquid propane delivery module ground circuit terminal 4 and the primary fuel pump supply circuit terminal 1.

17. Ignition OFF, verify the test lamp does not illuminate.

• If the test lamp illuminates

Refer to Primary Fuel Pump Testing

• If the test lamp turn does not illuminate

18. Ignition ON, verify the test lamp illuminates.

• If the test lamp does not illuminate

Refer to Primary Fuel Pump Testing

• If the test lamp illuminates

19. Ignition OFF, Connect the in-line harness connector to the liquid propane delivery module.

20. Ignition ON, verify the fuel pump operates.

• If the primary fuel pump does not operate

Test or replace the primary fuel pump

• If the primary fuel pump operates

21. Ignition OFF, disconnect the in-line harness connector at the liquid propane delivery module.

22. Connect a test lamp between liquid propane delivery module ground circuit terminal 4 and the purge control circuit terminal 3.

Note:
The purge valve is only energized during the first 5 seconds of ignition ON.

23. Ignition ON, verify the test lamp illuminates for 5-8 seconds and then turns OFF.

• If the test lamp does not illuminate for 5-8 s and then turn OFF

Refer to Purge Solenoid Testing

• If the test lamp illuminates for 5-8 s and then turns OFF

24. Connect the in-line harness connector at the liquid propane delivery module.

25. Ignition ON, verify the purge control solenoid operates.

• If the purge control solenoid does not operate

Test or replace the purge control solenoid.

• If the purge control valve operates

26. All OK

Liquid Propane Delivery Module Test

1. Ignition OFF, disconnect the in-line harness connector at the liquid propane delivery module.

2. Test for less than 10 ohms between the harness side of the in-line connector liquid propane delivery module ground circuit terminal 4 and ground.

• If 10 ohms or greater

1. Ignition OFF.

2. Test for less than 2 ohms in the ground circuit end to end.

• If 2 ohms or greater, repair the open/high resistance in the circuit.

• If less than 2 ohms, repair the open/high resistance in the ground connection.

• If less than 10 ohms

3. Test for 1 V or less between the following terminals on the harness side of the in-line connector and ground.

* Terminal 1 primary fuel pump voltage supply circuit

* Terminal 2 fuel supply solenoid and transfer pump voltage supply circuit

* Terminal 3 purge solenoid control circuit

• If greater than 1 V

Refer to the appropriate test

* Terminal 1 Primary Fuel Pump Testing

* Terminal 2 Fuel Supply Solenoid Testing

* Terminal 3 Purge Solenoid Testing

• If 1 V or less

4. Connect a test lamp on the harness side of the in-line between the purge solenoid control circuit terminal 3 and ground.

Note:
The purge solenoid is only energized during the first 5-8 seconds of ignition ON.

5. Ignition ON, verify the test lamp illuminates for 5-8 s and then turns OFF.

• If the test lamp does not illuminate

Refer to Purge Solenoid Testing

• If the test lamp remains illuminated

Test or replace the liquid propane control module.

• If the test lamp illuminates of 5-8 s and turns OFF.

6. Connect a test lamp on the harness side of the in-line between the fuel supply solenoid voltage supply circuit terminal 2 and ground.

7. Ignition ON, verify the test lamp illuminates

• If the test lamp does not illuminate

Refer to Fuel Solenoid Testing

• If the test lamp illuminates

8. Connect a test lamp on the harness side of the in-line between the primary fuel pump voltage supply circuit terminal 1 and ground.

9. Ignition ON, verify the test lamp illuminates

• If the test lamp does not illuminate

Refer to Primary Fuel Pump Testing

• If the test lamp illuminates

10. Evacuate the LPG from the fuel lines, refer to liquid propane evacuation.

11. Verify the pressure gauge displays 0 psi.

• If fuel pressure is not 0 psi or slowly increases

Replace the solenoid valves

• If fuel pressure is 0 psi and does not slowly increase

12. All OK

Primary Fuel Pump Test

1. Remove the primary fuel pump relay.

2. Connect a test lamp between the voltage supply circuit terminal E and ground. Verify the test lamp illuminates.

• If the test lamp does not illuminate

Repair the open or high resistance in the circuit

• If the test lamp illuminates

3. Connect a test lamp between the voltage supply circuit terminal F and ground. Verify the test lamp illuminates.

• If the test lamp does not illuminate

Repair the open or high resistance in the circuit

• If the test lamp illuminates

4. Connect a test lamp between the voltage supply circuit terminal E and the signal circuit terminal D.

5. Ignition OFF, verify the test lamp does not illuminate.

• If the test lamp does illuminate

1. Disconnect the harness connector at the liquid propane control module.

2. Test for infinite resistance between the signal circuit terminal D and ground.

• If less than infinite resistance, repair the short to ground in the circuit.

• If infinite resistance replace the liquid propane control module.

• If the test lamp does not illuminate

6. Ignition ON, verify the test lamp illuminates.

• If the test lamp does not illuminate

1. Disconnect the harness connector at the liquid propane control module.

2. Test for 2 ohms or less in the signal circuit end to end.

• If 2 ohms or less, replace the liquid propane control module.

• If greater than 2 ohms, repair the open or high resistance in the circuit.

• If the test lamp illuminates

7. Ignition OFF, install the primary fuel pump relay.

8. Disconnect the in-line harness connector at the liquid propane delivery module.

9. Connect a test lamp on the harness side of the in-line between the supply circuit terminal 1 and ground.

10. Ignition OFF, verify the test lamp does not illuminates.

• If the test lamp illuminates

1. Disconnect the primary fuel pump relay.

2. Test for less than 1 V on the supply circuit.

• If greater than 1 V, repair the short to voltage on the circuit.

• If less than 1 V, test or replace the primary fuel pump relay.

• If the test lamp does not illuminate

11. Ignition ON, verify the test lamp illuminates.

• If the test lamp does not illuminate

1. Disconnect the primary fuel pump relay.

2. Test for less than 2 ohms on the supply circuit end to end.

• If 2 ohms or greater , repair the open or high resistance on the circuit.

• If less than 2 ohms, test or replace the primary fuel pump relay.

• If the test lamp illuminates

12. Ignition OFF, connect a test lamp on the harness side of the in-line between the supply circuit terminal 1 and the ground circuit terminal 4.

• If the test lamp does not illuminate

Repair the open/high resistance in the ground circuit.

• If the test lamp illuminates

Test or replace the primary fuel pump.

Fuel Supply Solenoid Test

1. Remove the fuel supply solenoid relay.

2. Connect a test lamp between the voltage supply circuit terminal E and ground. Verify the test lamp illuminates.

• If the test lamp does not illuminate

Repair the open or high resistance in the circuit

• If the test lamp illuminates

3. Connect a test lamp between the voltage supply circuit terminal F and ground. Verify the test lamp illuminates.

• If the test lamp does not illuminate

Repair the open or high resistance in the circuit

• If the test lamp illuminates

4. Connect a test lamp between the voltage supply circuit terminal E and the signal circuit terminal D.

5. Ignition OFF, verify the test lamp does not illuminate.

• If the test lamp does illuminate

1. Disconnect the harness connector at the liquid propane control module.

2. Test for infinite resistance between the signal circuit terminal D and ground.

• If less than infinite resistance, repair the short to ground in the circuit.

• If infinite resistance replace the liquid propane control module.

• If the test lamp does not illuminate

6. Ignition ON, verify the test lamp illuminates.

• If the test lamp does not illuminate

1. Disconnect the harness connector at the liquid propane control module.

2. Test for 2 ohms or less in the signal circuit end to end.

• If 2 ohms or less, replace the liquid propane control module.

• If greater than 2 ohms, repair the open or high resistance in the circuit.

• If the test lamp illuminates

7. Ignition OFF, install the fuel supply solenoid relay.

8. Disconnect the in-line harness connector at the liquid propane delivery module.

9. Connect a test lamp on the harness side of the in-line between the supply circuit terminal 1 and ground.

10. Ignition OFF, verify the test lamp does not illuminates.

• If the test lamp illuminates

1. Disconnect the fuel supply solenoid relay.

2. Test for less than 1 V on the supply circuit.

• If greater than 1 V, repair the short to voltage on the circuit.

• If less than 1 V, test or replace the fuel supply solenoid relay.

• If the test lamp does not illuminate

11. Ignition ON, verify the test lamp illuminates.

• If the test lamp does not illuminate

1. Disconnect the fuel supply solenoid relay.

2. Test for less than 2 ohms on the supply circuit end to end.

• If 2 ohms or greater , repair the open or high resistance on the circuit.

• If less than 2 ohms, test or replace the primary fuel pump relay.

• If the test lamp illuminates

12. Ignition OFF, connect a test lamp on the harness side of the in-line between the supply circuit terminal 1 and the ground circuit terminal 4.

• If the test lamp does not illuminate

Repair the open/high resistance in the ground circuit.

• If the test lamp illuminates

Test or replace the fuel supply solenoid or scavenger pump.

Purge Solenoid Test

1. Disconnect the in-line harness connector at the liquid propane delivery module.

2. Connect a test lamp on the harness side of the in-line between the purge solenoid control circuit terminal 3 and ground.

3. Ignition OFF, verify the test lamp does not illuminates.

• If the test lamp illuminates

1. Disconnect the liquid propane control module.

2. Test for less than 1 V on the control circuit.

• If greater than 1 V, repair the short to voltage on the circuit.

• If less than 1 V, test or replace the liquid propane control module.

• If the test lamp does not illuminate

Note:
The purge solenoid is only energized during the first 5-8 seconds of ignition ON.

4. Ignition ON, verify the test lamp illuminates for 5-8 s and then turns OFF.

• If the test lamp does not illuminate

1. Disconnect the liquid propane control module.

2. Test for less than 2 ohms on the control circuit end to end.

• If 2 ohms or greater , repair the open or high resistance on the circuit.

• If less than 2 ohms, test or replace the liquid propane control module.

• If the test lamp remains illuminated

Test or replace the liquid propane control module.

• If the test lamp illuminates of 5-8 s and turns OFF.

5. Ignition OFF, connect a test lamp on the harness side of the in-line between the control circuit terminal 3 and the ground circuit terminal 4.

6. Ignition ON, verify the test lamp illuminates for 5-8 s and then turns OFF.

• If the test lamp does not illuminate

Repair the open/high resistance in the ground circuit.

• If the test lamp illuminates

Test or replace the purge solenoid.

Repair Instructions

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

* LPG Fuel Pump

* LPDM

* LPCM