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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 162 (ENGINE CONTROLS - SYSTEM & COMPONENT TESTS - 2.2L)FUEL SYSTEMS (GASOLINE)FUEL TANK LEAK TESTDIAGNOSTIC PROCEDURE
1999 GMC Forward Control 5.7 R, Automatic

Diagnostic Procedure

1999 GMC Forward Control 5.7 R, AutomaticSECTION Diagnostic Procedure
WARNING: This page is about a different car, the 2003 Pontiac Sunfire, 2003 Pontiac Grand Am, 2003 Oldsmobile Alero, and 2003 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
WARNING: Gasoline or gasoline vapors are highly flammable. A fire could occur if an ignition source is present. Never drain or store gasoline or diesel fuel in an open container, due to the possibility of fire or explosion. Have a dry chemical (Class B) fire extinguisher nearby.
  1. Did you perform the Diagnostic System Check - Engine Controls? If yes, go to next step. If no, go to DIAGNOSTIC SYSTEM CHECK - ENGINE CONTROLS under SELF-DIAGNOSTIC SYSTEM in SELF-DIAGNOSTICS - 2.2L ALERO, CAVALIER, GRAND AM & SUNFIRE - GASOLINE article.
  2. Raise and support vehicle. Inspect the fuel tank and fuel pipes for damage or external leaks. Did you find fuel leaking from the fuel tank? If yes, go to step  6. If no, go to next step.
  3. Turn ignition switch to RUN position, engine OFF. Using a scan tool, command the fuel pump ON. Inspect for fuel leaking from the fuel pipes. Did fuel leak from the fuel pipes? If yes, go to step  7. If no, go to next step.
  4. Install the Fuel Tank Cap (J 41415-40), or equivalent. Connect the Evaporative Emissions System Tester (EEST) (J 41413-200), or equivalent to the fuel tank cap adapter. See Fig 1 and Fig 2 . Using a scan tool, seal the EVAP system. Using the EEST, pressurize the fuel tank. Do not exceed 15 in. H2O. Did fuel leak from the fuel tank? If yes, go to step  6. If no, go to next step.
  5. Using the EEST, maintain pressure in the fuel tank. The fuel tank may need to be partially lowered. Using the Ultrasonic Leak Detector (J 41416), or equivalent, test for leaks above the fuel level in the following locations. See Fig 3.
    • The fuel tank, fill limiter vent valve, pressure relief valve and rollover valves.
    • The fuel sender housing and fuel sender seal.
    • The Fuel Tank Pressure (FTP) sensor seal.
    • The EVAP vapor pipes.
    • The fuel fill pipe, hose and fuel fill cap.

    Did you locate a fuel leak? If yes, go to next step. If no, see DIAGNOSTIC AIDS .

  6. Replace the fuel tank. After repair, go to step  8.
  7. Replace the leaking fuel pipe. After repair, go to next step.
  8. Operate the system to verify the repair. Did you correct the condition? If yes, system is okay at this time. If no, go to step  2.
Fig 1: Identifying Fuel Tank Cap Adapter (J 41415-40)
G00217371Courtesy of GENERAL MOTORS CORP.
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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.