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With Feedback Fuel System

WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.

System Description  - 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 two 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 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. Two fuel tanks store the fuel supply. An electric turbine style fuel pump attaches to the fuel sender assembly inside the left 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 pump also supplies fuel to a Venturi pump located on the bottom of the left fuel sender assembly. The function of the Venturi pump is to fill the fuel sender assembly reservoir. The primary fuel pressure regulator, a part of the left 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, the primary fuel pressure regulator, and the secondary fuel pressure regulator maintain fuel pressure in the fuel feed pipe and the fuel rail in order to prevent long cranking times. The fuel pump also supplies a small amount of pressurized fuel through the auxiliary fuel feed pipe to the siphon jet pump inside the right fuel tank. The pressurized fuel creates a Venturi action inside the siphon jet pump. The Venturi action causes the fuel to be drawn out of the right fuel tank. The fuel transfers from the right fuel tank to the left fuel tank through the auxiliary fuel return pipe. The auxiliary fuel return pipe inside the left fuel tank contains an anti-siphon hole in order to prevent fuel from siphoning from the left fuel tank into the right fuel tank. Both the auxiliary fuel feed pipe and the auxiliary fuel return pipe are located inside the convoluted stainless steel crossover hose. The right fuel sender assembly contains a secondary fuel pressure regulator. The secondary fuel pressure regulator has a lower set point than the primary regulator in order to allow fuel to flow to the siphon jet pump on the right fuel sender. When the engine is shut off, the pressure in the feed pipes immediately drops to the secondary regulator set point. This prevents the siphon jet pump from operating and in turn prevents the equalization of the left and right fuel tanks. The secondary fuel pressure regulator maintains fuel pressure in the auxiliary fuel feed pipe which reduces the time to prime the siphon jet pump. The pressurization also reduces fuel vaporization and boiling in the auxiliary fuel feed pipe.

Diagnostic Procedure

  1. 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.
    2. NOTE: Inspect the fuel system for damage or for external leaks before proceeding with this diagnostic.
  2. Turn ignition ON, with the engine OFF. Command fuel pump relay ON with a scan tool. Does the fuel pump operate? If fuel pump turns on and off, go to next step. If fuel pump does not turn on and off, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS  .
  3. 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  5 .
  4. Add 4 gal (15 L) of fuel. After adding fuel, go to next step.
    5. NOTE: The engine coolant temperature must be below the operating temperature in order to avoid irregular fuel pressure readings due to hot soak fuel boiling.
  5. Install Fuel Pressure gauge (J-34730-1A). See FUEL SYSTEM PRESSURE RELEASE  . Turn ignition ON, with the engine OFF. The fuel pump relay may need to be commanded ON a few times in order to obtain the highest possible fuel pressure. Command fuel pump relay ON with a scan tool. Observe Fuel Pressure gauge with fuel pump running. Is the fuel pressure within 55-62 psi (380-427 kPa)? If yes, go to next step. If no, go to step  13 .
    6. NOTE: The fuel pressure will decrease when the fuel pump stops operating. After fuel pump stops operating, fuel pressure should stabilize and remain constant.
  6. Observe Fuel Pressure Gauge for 5 minutes. Does fuel pressure decrease to less than 51 psi (350 kPa)? If yes, go to step  12 . If no, go to next step.
  7. Observe Fuel Level Sensor Right parameter. Is Fuel Level Sensor Right parameter less than 1 V? If yes, go to next step. If no, go to step  10 .
  8. Fill the fuel system until the Fuel Level Sensor Right parameter is more than 1 V. After completion, go to next step.
  9. Drain left fuel tank until Fuel Level Sensor Left parameter is less than 1.5 V. See FUEL TANK DRAINING under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. After completion, go to next step.
  10. Start the engine. Observe Fuel Level Sensor Left and Fuel Level Sensor Right parameters with a scan tool for 5 minutes. Does Fuel Level Sensor Right parameter decrease while Fuel Level Sensor Left parameter increases? If yes, go to next step. If no, go to step  15 .
  11. Operate the vehicle within the conditions to reproduce the original symptoms. Observe O2 and fuel trim parameters with a scan tool. Do the scan tool parameters indicate a lean condition? If yes, go to step  14 . If no, see SYMPTOMS in TROUBLE SHOOTING - NO CODES - 5.7L CORVETTE article.
  12. Turn ignition OFF. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. Disconnect the fuel feed hose from the 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 the fuel hose and the fuel rail pipe. Open the valve on 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 OFF with a scan tool. Close valve on fuel line shut-off adapter. Observe fuel pressure gauge for 1 minute. Does fuel pressure remain constant? If yes, go to step  15 . If no, go to step  22 .
  13. Is the fuel pressure more than 62 psi (427 kPa)? If yes, go to step  23 . If no, go to next step.
  14. Inspect fuel feed pipe and fuel feed rear pipe for a restriction. After repair is completed, go to step  26 If no restriction found, go to next step.
  15. Relieve the fuel pressure. See FUEL SYSTEM PRESSURE RELEASE  under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. Remove Fuel Line Shut-off Adapter, if previously installed. Connect fuel feed hose to fuel rail pipe, if previously disconnected. Remove fuel tank crossover tube/hose. See FUEL TANK CROSSOVER TUBE under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. Connect Evaporative Emissions System Tester (EEST) (J-41413-200) to one end of the 5/16 inch auxiliary fuel feed pipe inside of crossover tube/hose using appropriate hose and Brass Cone Adapter (J 41413-311) from EVAP Cap/Plug Kit (J 41413-300). Apply nitrogen to auxiliary fuel feed pipe. Cap other end of 5/16 inch auxiliary fuel feed pipe inside of crossover tube/hose using Small Red Cap (J-41413-306) from EVAP Cap/Plug Kit. Observe flow meter on EEST. Does flow meter indicate a leak? If yes, go to step  25 . If no, go to next step.
  16. Connect EEST to one end of 3/8 inch auxiliary fuel return pipe inside of crossover tube/hose using appropriate hose and Brass Cone Adapter from EVAP Cap/Plug Kit. Apply nitrogen to auxiliary fuel return pipe. Cap other end of 3/8 inch auxiliary fuel return pipe inside of crossover tube/hose using Small Black Cap (J-41413-307) from EVAP Cap/Plug Kit. Observe flow meter on EEST. Does flow meter indicate a leak? If yes, go to step  25 . If no, go to next step.
  17. Inspect for damaged "O" rings at the crossover hose to fuel tank connections. After replacing "O" rings, go to step  26 . If "O" ring replacement not necessary, go to next step.
  18. Connect EEST to 5/16 inch auxiliary fuel feed pipe inside of right fuel tank using appropriate hose and the Brass Cone Adapter from EVAP Cap/Plug Kit. Apply nitrogen to auxiliary fuel feed pipe. Observe flow meter on EEST. Doe flow meter indicate a leak? If yes, go to step  21 . If no, go to next step.
  19. Connect EEST to 5/16 inch auxiliary fuel feed pipe inside of left fuel tank using appropriate hose and Brass Cone Adapter from EVAP Cap/Plug Kit. Apply nitrogen to auxiliary fuel feed pipe. Observe flow meter on EEST. Does flow meter indicate a leak? If yes, go to next step. If no, go to step  23 .
  20. Remove left fuel sender assembly. See FUEL SENDER ASSEMBLY (WITH FEEDBACK FUEL SYSTEM) under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. Inspect auxiliary fuel feed and return pipes inside of left fuel tank for damage or restriction. After repair is completed, go to step  26 . If no problem found, go to step  23 .
  21. Remove the right fuel sender assembly. See FUEL SENDER ASSEMBLY (WITH FEEDBACK FUEL SYSTEM) under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. Inspect auxiliary fuel feed and return pipes inside of right fuel tank for damage or restriction. After repair is completed, go to step  26 . If no problem found, go to step  24 .
  22. 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  26 .
  23. Replace 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  26 .
  24. Replace right 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  26 .
  25. Replace the fuel tank crossover tube/hose. See FUEL TANK CROSSOVER TUBE under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. After repair is completed, go to next step.
  26. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to Step  5 .
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