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

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 fuel pressure regulator, and through the fuel feed pipe to the fuel injection system. The fuel pressure regulator has a T-joint that diverts the needed fuel to the fuel rail with the unused fuel dropping back into the reservoir of the primary fuel tank module. The primary fuel tank module 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.

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 for scan tool information

Special Tools

Important: 

•	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 relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure.

1. Ignition ON, command the fuel pump relay ON with a scan tool. You should hear the fuel pump turn ON and OFF.

⇒	If the fuel pump does not turn ON, refer to Fuel Pump Electrical Circuit Diagnosis .

2. Ignition OFF, all accessories OFF, install the J 34730-1A . Refer to Fuel Pressure Gage Installation and Removal .
3. 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.

Important: 

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

⇒	If less than the specified range, remove the fuel tank and test, inspect, and repair the items listed below. If all items test normal, replace the fuel pump.

•	Restricted fuel feed pipe

•	Restricted or plugged fuel filter

•	Restricted or plugged strainer

•	Stuck or binding fuel level float

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

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

Important: 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 the fuel pressure does not decrease greater than 34 kPa (5 psi) in 1 minute.

⇒	If greater than the specified range, perform the following procedure:

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

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

2.3.	Open the valve on the J 37287 .

2.4.	Ignition ON, command the fuel pump relay ON with a scan tool and bleed the air from the fuel pressure gage.

2.5.	Close the valve on the J 37287 .

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

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

2.7.	If the fuel system test normal, replace the fuel pump.

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

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

4. Remove the J 37287 and J 34730-1A . Refer to Fuel Pressure Gage Installation and Removal .
5. Operate the vehicle within the conditions of the customers concern while monitoring fuel related parameters with a scan tool. The scan tool parameters should not indicate a lean condition.

⇒	If the scan tool parameters indicate a lean condition, test for a restricted fuel feed pipe, restricted fuel filter, or poor connections at the harness connectors and ground circuits of the fuel pump. If all test normal, replace the fuel pump.

6. If the fuel system components test normal, refer to Symptoms - Engine Controls .

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.