Without Feedback Fuel System

Circuit Description - When you turn on the ignition switch, the control module enables 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 control module receives ignition reference pulses. If there are no ignition reference pulses, the control module shuts the fuel pump OFF within 2 seconds after the ignition was switched to the ON position or if the engine stops. The electric fuel pump is attached to the fuel sender assembly inside the left fuel tank. The in-tank fuel pump supplies fuel through a fuel feed pipe, and a fuel filter/fuel pressure regulator assembly, to the fuel rail. The fuel pump supplies fuel to the siphon jet pump in the right fuel tank. The siphon jet pump transfers fuel from the right fuel tank to the left fuel tank. The fuel pump provides fuel at a pressure greater than that needed by the fuel injectors. The fuel pressure regulator, part of the fuel filter, keeps the fuel available to the fuel injectors at a regulated pressure. Unused fuel returns to the left fuel tank by a separate fuel return pipe.

Test Description - The numbers below refer to the step numbers on the diagnostic table.

4

This step verifies that the vehicle is not out of fuel.

7

This step tests for an internal fuel leak.

10

This step tests for a loss of fuel pressure between the fuel feed pipe shut-off adapter and the fuel injectors.

11

This step tests for a loss of fuel pressure between the fuel feed pipe shut-off adapter and the fuel pump.

12

This step tests if the loss of fuel pressure is caused by the fuel pressure regulator, or by the check valve that is located in the fuel feed rear pipe.

15

This step determines if the fuel pressure regulator, or the fuel pump is the cause of the low fuel pressure.

16

This step verifies that there is an adequate supply of fuel to the siphon jet pump.

17

This step verifies the auxiliary fuel return rear pipe is not restricted.

Diagnostic Procedure

If diagnostic system check has already been performed, go to next step. If diagnostic system check has not been performed, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 5.7L CORVETTE article.

NOTE: Inspect the fuel system for damage or for external leaks before proceeding with this diagnostic.

Turn ignition ON, with the engine OFF. Command fuel pump relay ON with a scan tool. Does fuel pump operate? If yes, go to next step. If no, go to step FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS .
Observe Fuel Level Sensor Left parameter with a scan tool. Is Fuel Level Sensor Left parameter less than 0.8 V? If yes, go to next step. If no, go to step 6 .
Observe Fuel Level Sensor Right parameter with a scan tool. Is Fuel Level Sensor Right parameter less than 0.8 V? If yes, go to next step. If no, go to step 16 .
Add 5 gal. (19 L) of fuel. Operate vehicle within conditions of customer's concern. Does a driveability condition still exist? If yes, go to next step. If no, go to step 29 .
Turn ignition OFF. Turn OFF all accessories. Install a fuel pressure gauge. See FUEL SYSTEM PRESSURE RELEASE . Do Not start the engine. Command fuel pump relay ON with a scan tool. You may need to command fuel pump relay ON a few times in order to obtain highest possible fuel pressure. Observe fuel pressure gauge with fuel pump commanded ON. Is fuel pressure within 55-62 psi (380-427 kPa)? If yes, go to next step. If no, go to step 13 .

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.

Monitor fuel pressure gauge for 1 minute. Does fuel pressure decrease by more than 5 psi (34 kPa)? If yes, go to step 10 . If no, go to next step.
Relieve fuel pressure to 10 psi (69 kPa). Monitor fuel pressure gauge for 5 minutes. Does fuel pressure decrease by more than 2 psi (14 kPa)? If yes, go to step 28 . If no, go to next step.
Operate vehicle within conditions to reproduce original symptoms. Monitor O2 and fuel trim parameters with a scan tool. Does scan tool parameters indicate a lean condition? If yes, go to step 19 . If no see SYMPTOMS in TROUBLE SHOOTING - NO CODES - 5.7L CORVETTE article.
Turn ignition OFF. Relieve fuel pressure. Disconnect fuel feed hose from fuel rail pipe. See FUEL LINE DISCONNECT FITTINGS under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. Install Fuel Line Shut-Off Adapter (J 37287) between fuel hose and fuel rail pipe. Open the valve on Fuel Line Shut-Off Adapter. Command fuel pump relay ON with a scan tool. Bleed air from fuel pressure gauge. Command fuel pump relay ON and then OFF with a scan tool. Close fuel feed pipe shut-off valve. Monitor fuel pressure gauge for 1 minute. Does fuel pressure remain constant? If yes, go to next step. If no, go to step 23 .
Turn ignition OFF. Relieve fuel pressure. Remove fuel feed pipe shut-off adapter from the fuel rail. Connect fuel feed hose to fuel rail pipe. Raise and support vehicle. Disconnect fuel feed rear pipe from the left fuel sender. Install Fuel Line Shut-Off Adapter between fuel feed rear pipe and left fuel sender. Open valve in the Fuel Line Shut-Off Adapter. Turn ignition ON with the engine OFF. Command fuel pump relay ON with a scan tool. Bleed air from fuel pressure gauge. Command fuel pump relay ON and then OFF with a scan tool. Close fuel feed pipe shut-off valve. Observe fuel pressure gauge for 1 minute. Does fuel pressure remain constant? If yes, go to step 28 . If no, go to next step.
Turn ignition OFF. Open valve in fuel feed shut-off adapter. Relieve fuel pressure. Disconnect fuel return rear pipe from left fuel sender. Install Fuel Line Shut-Off Adapter between fuel return rear pipe and left fuel sender. Open valve in Fuel Line Shut-Off Adapter. Turn ignition ON with the engine OFF. Command fuel pump relay ON with a scan tool. Bleed the air from fuel pressure gauge. Command fuel pump relay ON and then OFF with a scan tool. Close Fuel Line Shut-Off Adapter. Monitor fuel pressure gauge for 1 minute. Does fuel pressure remain constant? If yes, go to step 25 . If no, go to step 26 .
Is fuel pressure above 62 psi (427 kPa)? If yes, go to next step. If no, go to step 15 .
Inspect fuel return rear pipe for a restriction. Repair as necessary. After repair is completed, go to step 29 . If no restriction found, go to step 25 .
Turn ignition OFF. Relieve fuel pressure. Disconnect fuel return rear pipe from left fuel sender. Install Fuel Line Shut-Off Adapter between fuel return rear pipe and left fuel sender. Open valve in Fuel Line Shut-Off Adapter. Turn ignition ON with the engine OFF. Command fuel pump relay ON with a scan tool. Bleed air from fuel system. Monitor fuel pressure gauge. Do not allow the fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage the fuel system. Slowly close the valve in Fuel Line Shut-Off Adapter. Command fuel pump relay ON with a scan tool. Does fuel pressure increase to more than 62 psi (427 kPa)? If yes, go to step 25 . If no, go to step 20 .

NOTE: DO NOT add more than 4 gal. (15 L) of fuel.

Add fuel to left fuel tank. Disconnect auxiliary fuel feed rear pipe from right fuel sender. Insert auxiliary fuel feed rear pipe into an approved gasoline container. You may need to command the fuel pump relay ON a few times in order to obtain specified time limit. Command the fuel pump relay ON for 10 seconds with a scan tool. Measure volume of fuel. Is volume of fuel greater than 0.633 pt (300 ml)? If yes, go to next step. If no, go to step 24 .

NOTE: Inspect the crossover hose if the right fuel tank is empty. Fuel flow to the right fuel tank is decreased during fueling if the crossover hose is collapsed or restricted.

Connect auxiliary fuel feed rear pipe to right fuel sender. Disconnect auxiliary fuel return rear pipe from left fuel sender. Insert auxiliary fuel return rear pipe into an approved gasoline container. Command fuel pump relay ON for 8 seconds with scan tool. Measure volume of fuel. Is volume of fuel greater than 0.703 pt (332.6 ml)? If yes, go to step 22 . If no, go to next step.
Inspect auxiliary fuel return rear pipe for a restriction. Repair as necessary. After repair is completed, go to step 29 . If no restriction found, go to step 27 .
Inspect fuel filter, fuel feed pipe and fuel feed rear pipe for a restriction. Repair as necessary. After repair is completed, go to step 29 . If no restriction found, go to step 28 .
Inspect harness connectors and ground circuits of fuel pump for poor connections. Repair as necessary. After repair is completed, go to step 29 . If no problem found, go to next step.
Remove left fuel sender assembly. See FUEL SENDER ASSEMBLY (WITH FEEDBACK FUEL SYSTEM) under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. Inspect fuel pump flex hose for damage, in tank fuel pump harness connectors for poor connections, fuel strainer for a restriction and fuel tank for contaminants. Repair as necessary. After repair is completed, go to step 29 . If no problem found, go to step 28 .
Repair restriction in the left fuel sender assembly. Repair as necessary. After repair is completed, go to step 29 .
Turn ignition OFF. Raise fuel rail, with fuel line connected. See FUEL RAIL & INJECTORS under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. Turn ignition ON, with the engine OFF. Command fuel pump relay ON with a scan tool. Locate and replace leaking fuel injector. After repair is completed, go to step 29 .
Locate and repair restriction in orifice located in the tee of the fuel feed rear pipe or auxiliary fuel feed rear pipe from the tee to the right fuel sender. After repair is completed, go to step 29 .
Replace fuel filter/regulator assembly. See FUEL FILTER/PRESSURE REGULATOR under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. After repair is completed, go to step 29 .
Replace fuel feed rear pipe with check valve. After repair is completed, go to step 29 .
Replace right fuel sender assembly. After repair is completed, go to step 29 .
Replace the left fuel sender assembly. See FUEL SENDER ASSEMBLY (WITH FEEDBACK FUEL SYSTEM) under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. After repair is completed, go to step 29 .
Operate system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step 3 .