GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2008 🢒 SRX 🢒 Preface 🢒 Cautions and Notices 🢒 Fuel Tank Leak Test

Diagnostic Instructions
    • Perform the Diagnostic System Check - Vehicle prior to using this diagnostic procedure.
    •  Review Strategy Based Diagnosis for an overview of the diagnostic approach.
    •  Diagnostic Procedure Instructions provides an overview of each diagnostic category.

Circuit/System Description

The fuel tank leak test is used to locate any fuel or fuel vapor escaping the fuel tank area. Fuel vapors escaping above the fuel level will be detected when the evaporative emission (EVAP) leak diagnostic completes one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP leak diagnostic completes 2 test cycles for a large leak or up to 8 test cycles for a small leak, only when a condition is detected.

Diagnostic Aids
    • Operate the vehicle under the condition of the customer concern. Under high temperature conditions fuel vapors may increase to the point of EVAP canister vapor saturation. Fuel vapors would then be released into the atmosphere. Once the engine is running and the EVAP purge is enabled, all fuel vapor release would be eliminated.
    • Movement of the EVAP pipes or the fuel pipes may help find an intermittent condition.
    • If the fuel level is low, a liquid fuel leak may not be evident.

Reference Information

Special Tools Required

    •  J 41413-200 Evaporative Emissions System Tester (EEST)
    • GE-41415-50 Interrupted Thread Cap Adapter

Circuit/System Verification

Caution: Place a dry chemical (Class B) fire extinguisher near the area before performing a Fuel Tank Leak Check. Before removing the fuel tank for a suspected leak, make sure that the fuel pipes or the tubes are not leaking onto the tank. Once removed, make sure that the fuel is not leaking around the fuel sender O-ring. Failure to follow these precautions may result in personal injury.

  1. Verify that the fuel tank and the fuel pipes are not damage or leaking.
    2. ⇒If you located a condition, repair as necessary.
  2. Ignition ON, command the fuel pump relay ON with a scan tool. Verify that the fuel pipes are not leaking.
    3. ⇒If you located a condition, repair as necessary.

    Important: Refer to the J 41413-200 Evaporative Emissions System Tester (EEST) operation manual for detailed instructions.

  3. Ignition OFF, install the J 41413-200 and the GE-41415-50 to the fuel filler pipe.
  4. Command the EVAP vent solenoid closed with a scan tool.
  5. Turn the nitrogen/smoke valve to Nitrogen and verify that there is no liquid fuel leak while the system is under pressure.
    6. ⇒If a leak is located, repair as necessary.

    Important: It may be necessary to partially lower the fuel tank.

  6. Using the J 41413-200 introduce smoke into the EVAP system. Verify that there are no vapor leaks in any of the following locations:
    7. • The fuel tank, the fill limiter vent valve, the pressure relief valve, and the grade vent valves
    • The fuel sender housing, the fuel sender seal, the fuel pipe, and the EVAP pipes
    • The fuel tank pressure (FTP) sensor seal
    • The fuel fill pipe and hose
         ⇒If a leak is observed, repair as necessary.