Spark

Fuel System Diagnosis

The engine control module (ECM) enables the fuel pump relay when the ignition switch is turned ON. The ECM will disable the fuel pump relay within 2 s unless the ECM detects ignition reference pulses. The ECM continues to enable the fuel pump relay as long as ignition reference pulses are detected. The ECM disables the fuel pump relay within 2 s if ignition reference pulses cease to be detected and the ignition remains ON.

The fuel system is a returnless on-demand design. The fuel pressure regulator is a part of the fuel sender assembly, eliminating the need for a return pipe from the engine. A returnless fuel system reduces the internal temperature of the fuel tank by not returning hot fuel from the engine to the fuel tank. Reducing the internal temperature of the fuel tank results in lower evaporative emissions.

The fuel tank stores the fuel supply. An electric turbine-style fuel pump is attached to the fuel sender assembly inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel filter and the fuel feed pipe to the fuel injection system. The fuel pump provides fuel at a higher rate of flow than is needed by the fuel injection system. The fuel pressure regulator, a part of the fuel sender assembly, maintains the correct fuel pressure to the fuel injection system. The fuel pump and sender assembly contains a reverse flow check valve. The check valve and the fuel pressure regulator maintain fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times.

Electrical Information Reference

Scan Tool Reference

Control Module References

Special Tools

CH-48027 Digital Pressure Gauge

For equivalent regional tools, refer to Special Tools .

Note: 

1. Ignition ON, engine OFF, command the KR23A Fuel Pump Relay ON with a scan tool. You should hear the G12 Fuel Pump turn ON and OFF.

⇒	If the G12 Fuel Pump does not operate, refer to Fuel Pump Electrical Circuit Diagnosis .

2. Ignition OFF, all accessories OFF, install a CH-48027 gauge. Refer to Fuel Pressure Gauge Installation and Removal .
3. Ignition ON, engine OFF, command the KR23A Fuel Pump Relay ON with a scan tool. Verify the fuel pressure is 345-425 kPa (50-62 psi) and does not decrease more than 34 kPa (5 psi) in 1 min.

Note: 

•	The KR23A 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.

1. Ignition ON, engine OFF, command the KR23A Fuel Pump Relay ON with a scan tool. Verify that the fuel pressure is 345-425 kPa (50-62 psi) on the CH-48027 gauge while the G12 fuel pump is operating.

⇒	If the fuel pressure is greater than the specified range, replace the G12 Fuel Pump.

⇒	If the fuel pressure is less than the specified range, test, inspect, and repair the items listed below. If all items test normal, replace the G12 Fuel Pump.

•	Restricted fuel feed pipe

•	Restricted or clogged strainer

•	Inspect the G12 fuel pump harness connectors and the ground circuits of the G12 fuel pump for poor connections.

2. Verify that the fuel pressure does not decrease more than 34 kPa (5 psi) in 1 min.

⇒	If the fuel pressure decreases more than the specified range, locate and replace the leaking component.

3. Relieve the fuel pressure to 69 kPa (10 psi). Verify that the fuel pressure does not decrease more than 14 kPa (2 psi) in 5 min.

⇒	If the fuel pressure decreases more than the specified range, replace the G12 Fuel Pump module.

4. Operate the vehicle within the conditions of the customers concern while monitoring the fuel pressure with the CH -48027 gauge. The fuel pressure should not drop off during acceleration, cruise or hard cornering.

⇒	If the fuel pressure drops off, test, inspect, and repair the items listed below. If all items test normal, replace the G12 Fuel Pump.

•	Restricted fuel feed pipe

•	Restricted or clogged strainer

•	Inspect the harness connectors and the ground circuits of the G12 Fuel Pump for poor connections.

5. If the fuel system tests normal, refer to Symptoms - Engine Controls .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.