Spark

Fuel Pump Electrical Circuit Diagnosis

When you turn ON the ignition switch, the engine control module (ECM) energises the fuel pump relay which powers the fuel pump ON. The fuel pump remains ON as long as the engine is cranking or running and the ECM receives ignition reference pulses. If there are no ignition reference pulses, the ECM shuts the fuel pump OFF within 2 s after the ignition was switched to the ON position or if the engine stops.

The following conditions may cause the fuel pump fuse to open:

Schematic Reference

Engine Controls Schematics : Siemens ECM - LPG with LCP → Siemens ECM - Gas without FX3 or LCP → Delphi ECM - FX3

Connector End View Reference

Component Connector End Views

Description and Operation

Fuel System Description

Electrical Information Reference

Scan Tool Reference

Control Module References

Special Tools

EL-43244 Relay Puller Pliers

For equivalent regional tools, refer to Special Tools .

With the ignition ON, engine OFF, command the fuel pump relay ON and OFF several times using the scan tool output control function. You should either hear or feel the relay click and the fuel pump should turn ON and OFF with each command.

1. Ignition OFF, the fuel pump should not be running.

⇒	If the fuel pump runs continuously, test the relay controlled output circuit terminal 87 of the KR23A fuel pump relay for a short to voltage. If the circuit tests normal, replace the KR23A fuel pump relay.

2. Ignition OFF, remove the KR23A fuel pump relay from the electrical centre with the EL 43244 relay puller pliers.
3. Ignition ON, verify a test lamp illuminates between the relay coil ignition circuit terminal 85 and ground.

⇒	If the test lamp does not illuminate, repair the relay coil ignition circuit for a short circuit to ground or an open/high resistance.

4. Ignition OFF, connect a test lamp between the relay coil control circuit terminal 86 and the relay coil ignition circuit terminal 85.
5. Ignition ON, command the fuel pump relay ON and OFF with a scan tool. The test lamp should turn ON and OFF with each command.

⇒	If the test lamp is always ON, test the relay coil control circuit for a short to ground. If the circuit tests normal, replace the K20 ECM.

⇒	If the test lamp is always OFF, test the relay coil control circuit for a short to voltage or an open/high resistance. If circuit tests normal, replace the K20 ECM.

6. Verify a test lamp illuminates between the relay switch B+ circuit terminal 30 and ground.

⇒	If the test lamp does not illuminate, repair the relay switch B+ circuit for a short circuit to ground or an open/high resistance.

7. Install a 15A fused jumper wire between the relay switch B+ circuit terminal 30 and the relay controlled output circuit terminal 87. Verify the G12 fuel pump turns ON.

⇒	If the fuel pump does not turn ON, test for the following conditions:

•	An open/high resistance in the relay controlled output circuit

•	An open/high resistance in the fuel pump ground circuit

⇒	If the above circuits test normal, replace the G12 fuel pump.

8. If all circuits test normal, test or replace the KR23A fuel pump relay.

1. Ignition OFF, remove the KR23A fuel pump relay from the electrical centre with the EL 43244 relay puller pliers.
2. Test for 70-110 Ω between terminals 85 and 86.

⇒	If not within the specified range, replace the KR23A fuel pump relay

3. Test for infinite resistance between the following terminals:

•

30 and 86

•

30 and 87

•

30 and 85

•

85 and 87

⇒	If not the specified range, replace the KR23A fuel pump relay.

4. Install a 20 A fused jumper wire between KR23A fuel pump relay terminal 85 and 12 V. Install a jumper wire between KR23A fuel pump relay terminal 86 and ground. Test for less than 2 Ω between terminals 30 and 87.

⇒	If greater than the specified range, replace the KR23A fuel pump relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.