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Home >> Cadillac >> 2002 >> Escalade EXT >> Repair and Diagnosis (Single Page) >> Engine Performance >> System >> Engine Controls - Basic Diagnostic Procedures >> Basic Fuel System Checks (Gasoline) >> Fuel System Pressure Test (2.2L SONOMA & S10 Pickup) >> Diagnostic Procedure
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Diagnostic Procedure

  1. Perform OBD system check. See DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L SONOMA & S10 PICKUP article. After performing OBD system check, go to next step.
    2. IMPORTANT: Inspect the fuel system for damage, or external leaks, before proceeding wit 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, diagnose fuel pump electrical circuit.
    3. IMPORTANT: Verify there is adequate fuel in the tank before proceeding with this diagnostic.
  3. Turn ignition off. Turn off all accessories Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Install Fuel Pressure Gauge (J-34730-FF). Turn ignition on, with engine off. Command fuel pump ON with scan tool. It may be necessary to command the fuel pump on a few times in order to obtain the highest possible fuel pressure. Observe fuel pressure gauge with fuel pump commanded ON. Is fuel pressure 56-62 psi (386-427 kPa)? If yes, go to next step. If no, go to step  9.
    4. IMPORTANT: Fuel pressure may vary slightly when fuel pump stops. After fuel pump stops, fuel pressure should stabilize and remain constant.
  4. Monitor the fuel pressure gauge for one minute. If fuel pressure decreases more than 5 psi (34 kPa) in one minute, go to step  7. If fuel pressure does not decrease more than 5 psi (34 kPa) in one minute, go to next step.
  5. 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  17. If no, go to next step.
  6. Operate the vehicle within the conditions to reproduce the original symptoms. Monitor O2 and fuel trim parameters with a scan tool. Do the scan tool parameters indicate a lean condition? If yes, go to step  12. If no, see INTERMITTENTS in TROUBLE SHOOTING - NO CODES - 2.2L SONOMA & S10 PICKUP article.
  7. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Disconnect fuel feed hose from fuel rail. Install Fuel Line Shut-Off Adapter (J-37287) between fuel hose and fuel rail. Open valve on fuel pipe shut-off adapter. Turn ignition on, with engine off. Command fuel pump ON with scan tool. Bleed air from fuel pressure gauge. Command fuel pump ON and then OFF with scan tool. Close fuel feed pipe shut-off valve. Monitor fuel pressure gauge for one minute. Does the fuel pressure remain constant? If yes, go to next step. If no, go to step  15.
  8. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Open fuel feed pipe shut-off valve. Raise and support vehicle. Disconnect fuel return pipe from fuel filter. Install Fuel Line Shut-Off Adapter (J-37287) between fuel return pipe and fuel filter. Open fuel return pipe shut-off valve. Turn ignition on, with engine off. Command fuel pump ON with scan tool. Bleed air from fuel pressure gauge. Command fuel pump ON and then OFF with a scan tool. Close the fuel return pipe shut-off valve. Monitor the fuel pressure gauge for one minute. Does fuel pressure remain constant? If yes, go to step  16. If no, go to step  17.
  9. Is the fuel pressure greater than 62 psi (427 kPa)? If no, go to step  11. If yes, go to next step.
  10. Inspect the fuel return pipe and for a restriction. Repair as necessary, then go to step  18. If repair is not necessary, go to step  16.
  11. Turn ignition off. Relieve fuel pressure. See FUEL SYSTEM PRESSURE RELEASE . Raise and support vehicle. Disconnect fuel return pipe from fuel filter. Install Fuel Line Shut-Off Adapter (J-37287) between fuel return pipe and fuel filter. Open the valve in the fuel pipe shut-off adapter. Turn ignition on, with engine off. Bleed air from the fuel pressure gauge. Monitor fuel pressure gauge. DO NOT allow fuel pressure to exceed 75 psi (517 kPa). Excessive pressure may damage fuel system. Command fuel pump ON with a scan tool. Slowly close the valve in the fuel return pipe shut-off adapter, while the fuel pump is operating. Does the fuel pressure increase to greater than 62 psi (427 kPa)? If yes, go to step  15. If no, go to next step.
  12. Inspect for a restricted fuel filter or fuel feed pipe. Did you find and correct the condition? If yes, go to step  18. If no, go to next step.
  13. Inspect the harness connectors and the ground circuits of the fuel pump for poor connections. Did you find and correct the condition? If yes, go to step  18. If no, go to next step.
  14. 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 fuel tank for contaminants. Did you find and correct the condition? If yes, go to step  18. If no, go to step  17.
  15. Turn ignition off. Raise fuel rail assembly with fuel pipe connected. Turn ignition on, with engine off. Command fuel pump ON with scan tool. Locate and replace leaking fuel injector. After repairs, go to step  18.
  16. Replace fuel filter. After replacing fuel filter, go to step  18.
  17. Replace fuel sender. After replacing fuel sender, go to next step.
  18. 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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