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HOMESERVICE MANUALSCHEVROLET2002IMPALA LSREPAIR AND DIAGNOSISENGINE PERFORMANCETESTING & DIAGNOSISENGINE CONTROL SYSTEM - BASIC DIAGNOSTIC PROCEDURESNO-START DIAGNOSISNO START - ENGINE CRANKS OKAY (3.5L & 4.0L AURORA)FUEL SYSTEM DIAGNOSIS
2002 Chevrolet Impala LS

Fuel System Diagnosis

2002 Chevrolet Impala LSSECTION Fuel System Diagnosis
  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 DIAGNOSTIC SYSTEM CHECKS in appropriate SELF-DIAGNOSTICS article.
    2. NOTE: Inspect fuel system for damage or external leaks before proceeding with this diagnostic.
  2. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Does fuel pump operate? If yes, go to next step. If no, go to FUEL PUMP ELECTRICAL CIRCUIT DIAGNOSIS .
    3. NOTE: Ensure there is adequate fuel in fuel tank before proceeding with this diagnostic
  3. Turn ignition off. Turn off all accessories. Install Fuel Pressure Gauge (J-34730-1A). Place bleed hose from fuel pressure gauge into an approved gasoline container. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Bleed air out of fuel pressure gauge. It may be necessary to command the fuel pump on several times in order to obtain the highest possible fuel pressure. DO NOT start engine. Observe fuel pressure gauge, with fuel pump commanded on. Is fuel pressure within 41-47 psi (2.9-3.3 kg/cm 2 ). If yes, go to next step. If no, go to step  12.
    4. NOTE: Fuel pressure may vary slightly when fuel pump stops running. After fuel pump stops running, fuel pressure should stabilize and remain constant.
  4. Monitor fuel pressure gauge for one minute. Does fuel pressure drop more than 5 psi (0.4 kg/cm 2 )? If yes, go to step  9. If no, go to next step.
  5. Relieve fuel pressure to 10 psi (0.7 kg/cm 2 ). Monitor fuel pressure gauge for 5 minutes. Does fuel drop more than 2 psi (0.1 kg/cm 2 ). If yes, go to step  24. If no, go to next step.
  6. Turn ignition off for 15 seconds. Turn ignition on, with engine off. Monitor fuel pressure gauge. Start engine. Does fuel pressure drop to 3-10 psi (0.2-0.7 kg/cm 2 ) when engine is started? If yes, go to next step. If no, go to step  8.
  7. Operate vehicle within the conditions of the customer's concern. Monitor fuel related parameters with a scan tool. Do any of the scan tool parameters indicate a lean condition? If yes, go to step  17. If no, see appropriate TROUBLE SHOOTING - NO CODES article.
  8. Disconnect vacuum hose from fuel pressure regulator. Operate engine at idle. Monitor fuel pressure gauge. Using a hand-held vacuum pump, apply 12-14 in. Hg (40-47 kPa) to fuel pressure regulator. Does the fuel pressure drop 3-10 psi (0.2-0.7 kg/cm 2 ) when vacuum is applied? If yes, go to step  21. If no, go to step  23.
  9. Turn ignition off. Disconnect vacuum hose from fuel pressure regulator. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Inspect for fuel leak from fuel pressure regulator vacuum port. Is fuel pressure regulator leaking fuel? If yes, go to step  23. If no, go to next step.
  10. Turn ignition off. Relieve fuel pressure. Disconnect fuel feed hose and fuel return hose from fuel rail pipes. Install Fuel Pipe Shut-Off Adapters (J-37287) between the fuel hoses and fuel rail pipes. Open valves on the fuel pipe shut-off adapters. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Bleed air from fuel pressure gauge. Command the fuel pump on and then off. Close fuel feed pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does the fuel pressure remain constant? If yes, go to step  19. If no, go to next step.
  11. Turn ignition off. Open fuel feed pipe shut-off valve. Turn ignition on, with engine off. Command fuel pump on and then off with a scan tool. Close the fuel return pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does fuel pressure remain constant? If yes, go to step  23. If no, go to step  20.
  12. Is fuel pressure greater than 62 psi (4.4 kg/cm 2 )? If yes, go to step  14. If no, go to next step.
  13. Is fuel pressure greater than zero psi? If yes, go to step  16. If no, go to step  17.
  14. Turn ignition off. Relieve fuel pressure. Disconnect fuel return hose from fuel rail pipe. Attach a length of flexible fuel hose to fuel rail outlet passage. Place open end of fuel hose into an approved gasoline container. Turn ignition on, with engine off. Monitor fuel pressure gauge while fuel pump is operating. Is fuel pressure within 41-47 psi (2.9-3.3 kg/cm 2 )? If yes, go to step  22. If no, go to next step.
  15. Inspect fuel return pipe and fuel rail outlet passage for restriction. Did you find and correct the condition? If yes, go to step  25. If no, go to step  23.
  16. Turn ignition off. Relieve fuel pressure. Disconnect fuel return hose from fuel rail pipe. Install Fuel Pipe Shut-Off Adapters (J-37287) between fuel return pipe and fuel rail. Open valve in fuel pipe shut-off adapter. Turn ignition on, with engine off. Command fuel pump on with scan tool. Bleed air from fuel system. Monitor fuel pressure gauge. Slowly close the valve in fuel return pipe shut-off adapter. Command fuel pump on with scan tool. Does the fuel pressure rise to more than 47 psi (3.3 kg/cm 2 )? If yes, go to step  23. If no, go to next step.
  17. Check for restriction in fuel filter and fuel feed pipe. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  18. Inspect the harness connectors and ground circuits of fuel pump for poor connections. Did you find and correct the condition? If yes, go to step  25. If no, go to next step.
  19. Remove fuel sender assembly. Inspect fuel pump flex hose for damage, in-tank fuel pump harness connectors for poor connections, fuel strainer for a restriction or contaminates in fuel tank. Did you find and correct the condition? If yes, go to step  25. If no, go to step  24.
  20. Turn ignition off. Raise fuel rail with fuel lines connected. Turn ignition on, with engine off. Using scan tool, command fuel pump on. Locate and replace leaking fuel injector(s). After repairs, go to step  25.
  21. Repair vacuum source to fuel pressure regulator. After repairs, go to step  25.
  22. Locate and repair the restricted fuel return line. After repairs, go to step  25.
  23. Replace fuel pressure regulator. After repairs, go to step  25.
  24. Replace fuel pump. After repairs, go to step, go to next step.
  25. Operate the system in order to verify the repair. Did you correct the condition? If yes, system is okay. If no, go to step  3.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.