The engine control module (ECM) supplies a high voltage signal to the fuel pump control module (FPCM) when the ECM detects that the ignition is ON. The high voltage signal from the ECM to the FPCM remains active for two seconds, unless the engine is in Crank or Run. While this signal is being received, the FPCM closes the ground switch of the fuel pump and also supplies a varying voltage to the fuel tank pump module in order to maintain the desired fuel rail pressure.

The fuel system is an electronic returnless on-demand design. 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 and the fuel feed pipe to the fuel injection system. The primary fuel tank module contains a reverse flow check valve. The check valve maintains 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 Required

Important: 

1. Ignition OFF, all accessories OFF, install a CH-48027-100 . Refer to Fuel Pressure Gage Installation and Removal.
2. Ignition ON, engine OFF, command the fuel pump ON with a scan tool. Verify the fuel pressure is between 345-414 kPa (50-60 psi) and does not decrease more than 100 kPa (14.5 psi) in 5 minutes.

Important: 

•	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 ON, engine OFF, command the fuel pump ON with a scan tool and observe the fuel pressure gage while the fuel pump is operating. Verify the fuel pressure is between 345-414 kPa (50-60 psi).

⇒	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 primary fuel tank module.

•	Restricted fuel feed pipe

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

2. Verify that the fuel pressure does not decrease more than 100 kPa (14.5 psi) in 5 minutes.

⇒	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.	Disconnect the chassis fuel feed hose from the engine compartment fuel pipe. Refer to Metal Collar Quick Connect Fitting Service.

2.3.	Connect the chassis fuel feed hose to the inlet side of SA9127E-7 using the J 43937 .

2.4.	Connect the engine compartment fuel pipe to the ON/OFF valve side of the SA9127E-7 using the J 43937 .

2.5.	Cap the pressure test port on the SA9127E-7 with the J 43936 .

2.6.	Open the valve on the SA9127E-7 .

2.7.	Ignition ON, command the fuel pump ON with a scan tool and bleed the air from the CH-48027-100 .

2.8.	Command the fuel pump ON for a minimum of 10 seconds with a scan tool.

2.9.	Close the valve on the SA9127E-7 .

2.10.

Monitor the fuel pressure for 5 minutes.

⇒	If the fuel pressure decreases more than 55 kPa (8 psi) within the specified time, locate and replace the leaking fuel injectors.

⇒	If the fuel pressure does not decrease more than 55 kPa (8 psi) within the specified time, replace the primary fuel tank module.

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 primary fuel tank module.

4. Operate the vehicle within the conditions of the customer's concern while monitoring the fuel pressure with the CH-48027-100 . 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 primary fuel tank module.

•	Restricted fuel feed pipe

•	Inspect the harness connectors and the ground circuits of the 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.