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Diagnostic Procedure (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.
  1. Did you perform the Diagnostic System Check-Engine Controls? If yes, go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS in SELF-DIAGNOSTICS - 5.7L CORVETTE article.
  2. Did you perform the Fuel Injector Coil Test? If yes, go to next step. If no, see FUEL INJECTOR COIL TEST  .
    3. NOTE: DO NOT perform this test if the ECT is above 201°F (94°C). Verify that adequate fuel is in the fuel tank before proceeding with this diagnostic.

    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.

  3. Install fuel pressure gauge. Turn ignition ON, with the engine OFF. Command fuel pump relay ON with a scan tool. Observe the fuel pressure gauge, with fuel pump relay commanded ON. Is the fuel pressure 55-62 psi (380-427 kPa)? If yes, go to next step. If no, see FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 5.7L CORVETTE article.
    4. NOTE: The fuel pressure will decrease when the fuel pump stops operating. After the fuel pump stops operating, the fuel pressure should stabilize and remain constant.
  4. Monitor fuel pressure gauge for 5 minutes. Does fuel pressure decrease by more than 51 psi (380 kPa)? If yes, see FUEL SYSTEM DIAGNOSIS under FUEL SYSTEMS in BASIC DIAGNOSTIC PROCEDURES - 5.7L CORVETTE article. If no, go to next step.
    5. NOTE: DO NOT repeat any portion of this test before running the engine in order to prevent the engine from flooding. Record the fuel pressure value immediately after the fuel injector stops pulsing. The fuel pressure may rise after the fuel injector stops pulsing. DO NOT record the higher fuel pressure value.
    • Select the FUEL INJECTOR BALANCE TEST function with a scan tool.
    • Select an injector to be tested.
    • Press ENTER. This will prime the fuel system.
    • Record the fuel pressure indicated by the fuel pressure gauge after the fuel pressure stabilizes. This is the 1st pressure reading.
    • Energize the fuel injector by depressing the PULSE INJECTOR BUTTON on the scan tool. This will energize the injector and decrease the fuel pressure.
    • Record the fuel pressure indicated by the fuel pressure gauge after the fuel injector has stopped pulsing. This is the 2nd pressure reading.
    • Press ENTER again to bring you back to the SELECT INJECTOR screen.
    • Repeat for each fuel injector.
    • Subtract the 2nd pressure reading from the 1st pressure reading for one fuel injector. The result is the pressure drop value.
    • Obtain a pressure drop value for each fuel injector.
    • Add all of the individual pressure drop values. This is the total pressure drop.
    • Divide the total pressure drop by the number of fuel injectors. This is the average pressure drop.

    Is the difference between any individual pressure drop and the average pressure drop more than 1.5 psi (10 kPa)? If yes go to next step. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS in SELF-DIAGNOSTICS - 5.7L CORVETTE article.

  6. Replace affected fuel injector. See FUEL RAIL & INJECTORS under FUEL SYSTEMS in REMOVAL & INSTALLATION - CORVETTE article. After repair is complete, go to next step.
  7. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, see DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS in SELF-DIAGNOSTICS - 5.7L CORVETTE article.
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