The control module enables the fuel pump when the ignition switch is turned ON. The control module will disable the fuel pump within 2 seconds unless the control module detects ignition reference pulses. The control module continues to enable the fuel pump as long as ignition reference pulses are detected. The control module disables the fuel pump within 2 seconds 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 primary fuel tank module, 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.

An electric turbine style fuel pump attaches to the primary fuel tank module inside the fuel tank. The fuel pump supplies high pressure fuel through the fuel filter, past the pressure relief valve, and through the fuel feed pipe to the fuel injection system.

The primary fuel tank module also contains a primary jet pump and a secondary jet pump. Fuel pump flow loss, caused by vapor expulsion in the pump inlet chamber, is diverted to the primary jet pump and the secondary jet pump through a restrictive orifice located on the pump cover. The primary jet pump fills the reservoir of the primary fuel tank module. The secondary jet pump creates a venturi action which causes the fuel to be drawn from the secondary side of the fuel tank, through the fuel transfer pipe, to the primary side of the fuel tank.

Description and Operation

Fuel System Description

Electrical Information Reference

Scan Tool Reference

Control Module References

Special Tools

Note: 

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

•	Verify that adequate fuel is in the fuel tank before proceeding.

•	The fuel pump 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 OFF, all accessories OFF, install the J 37287 adapters and CH 48027 gage . Refer to Fuel Pressure Gage Installation and Removal
2. Ignition ON, command the fuel pump relay ON with a scan tool. Verify the fuel pressure is between 380-410 kPa (55-60 psi) and remains steady for 5 minutes.

1. Ignition ON, command the fuel pump ON with a scan tool and observe the fuel pressure while the fuel pump is operating. Verify the fuel pressure is between 380-410 kPa (55-60 psi).

⇒	If the fuel pressure is more than the specified range, replace the fuel pump.

⇒	If the fuel pressure is less than the specified range, remove the fuel tank and test/inspect for the following:

•	Restricted fuel feed pipe

•	Restricted or plugged fuel filter

•	Restricted or plugged strainer

•	Stuck or binding fuel level float

•	Restricted siphon jet pump

•	Restricted transfer lines between fuel tanks

•	Faulty pressure relief valve

•	Poor connections at the harness connectors and ground circuits of the fuel pump

⇒	If you find a condition, repair as necessary.

⇒	If all components test normal, replace the fuel pump.

Note: The fuel pressure may vary slightly when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.

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

⇒	If the fuel pressure decreases more than the specified value, perform the following procedure:

2.1.	Ignition OFF, relieve the fuel pressure. Refer to Fuel Pressure Relief.

2.2.	Install the J 37287 adapters between the fuel feed pipe and the fuel rail.

2.3.	Open the valve on the J 37287 adapters .

2.4.	Bleed the air from the fuel pressure gage.

2.5.	Close the valve on the J 37287 adapters .

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

⇒	If the fuel pressure remains constant, replace the fuel pump.

⇒	If the fuel pressure drops, locate and replace the leaking fuel injector.

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 minutes.

⇒	If the fuel pressure decreases more than the specified value, replace the fuel pump.

4. Remove the J 37287 adapters and CH 48027 gage . Refer to Fuel Pressure Gage Installation and Removal.
5. Operate the vehicle within the conditions of the customer concern while monitoring fuel related parameters with a scan tool.

⇒	If the scan tool parameters indicate a lean condition, test/inspect for the following:

•	Restricted fuel feed pipe

•	Restricted fuel filter

•	Restricted siphon jet pump

•	Restricted transfer lines between fuel tanks

•	Faulty pressure relief valve

•	Poor connections at the harness connectors and ground circuits of the fuel pump

⇒	If all components test normal and the scan tool parameters indicate a lean condition, replace the fuel pump.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.