GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 Yukon XL - 4WD 🢒 Engine 🢒 Engine Controls - 4.8L, 5.3L, and 6.0L 🢒 Fuel Tank Leak Test

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) diagnostics complete one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP diagnostics complete two test cycles.

Diagnostic Aids
    • Operate the vehicle under the condition of the customers 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 EVAP purge is enabled, all fuel vapor release would be eliminated.
    • Test for fuel leaking in the following locations:
       - The fuel tank
       - The rear tank--if applicable
       - The fuel feed and return pipes
    • Test for fuel vapor leaks in the following locations:
       - The fuel tank, fill limiter vent valve, and rollover valves
       - The rear fuel tank and rollover valves--if applicable
       - The fuel fill pipe, hose and fuel fill cap
       - The rear fuel fill pipe, hose and fuel fill cap if applicable
       - The fuel sender housing and seal
       - The rear fuel sender housing and seal if applicable
       - The fuel tank pressure (FTP) sensor seal
       - The EVAP vapor pipe
    • Movement of the EVAP pipes or fuel pipes may help find an intermittent condition.

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. This step tests for fuel leaks below the fuel tank fuel level.

    2.

  2. This step test is to locates fuel vapors escaping above the fuel level in the fuel tank .

Fuel Tank Leak Test

Step

Action

Yes

No

1

Did you perform the Diagnostic System Check-Engine Controls?

Go to Step 2

Go to Diagnostic System Check - Engine Controls

2

Important: Before performing this procedure, place a dry chemical (class B) fire extinguisher near the work area.

  1. Raise the vehicle. Refer to Lifting and Jacking the Vehicle in General Information.
  2. Inspect the fuel tank and fuel pipes for damage or external leaks.

Did you find fuel leaking from the fuel tank?

Go to Step 6

Go to Step 3

3

  1. Turn ON the ignition, with the engine OFF.
  2. Command the fuel pump relay ON with a scan tool.
  3. Inspect for fuel leaking from the fuel pipes.

Did you find fuel leaking from the fuel pipes?

Go to Step 7

Go to Step 4

4

  1. Install the J 41415-40 Fuel Tank Cap Adaptor.
  2. Connect the J 41413-200 Evaporative Emissions System Tester (EEST) to the fuel tank cap adaptor.
  3. Seal the EVAP system with a scan tool.

    4. Important : Do not exceed 15 in H2O.

  4. Pressurize the fuel tank with the J 41413-200 .

Did you find fuel leaking from the fuel tank?

Go to Step 6

Go to Step 5

5

  1. Maintain pressure in the fuel tank with the J 41413-200 .

    2. Important: It may be necessary to partially lower the fuel tank. Refer to Fuel Tank Replacement .

  2. With the J 41416 Ultrasonic Leak Detector, test for leaks above the fuel level in the following locations.
    3. • The fuel tank, fill limiter vent valve, pressure relief valve and rollover valves--Refer to Fuel Tank Replacement .
    • The fuel sender housing and fuel sender seal--Refer to Fuel Sender Assembly Replacement .
    • The fuel tank pressure (FTP) sensor seal--Refer to Fuel Tank Pressure Sensor Replacement .
    • The fuel fill pipe and hose--Refer to Filler Tube Replacement .
    • If equipped with a rear tank, the fuel tank, fill limiter vent valve, pressure relief valve and rollover valves--Refer to Fuel Tank Replacement .
    • If equipped with a rear tank, the fuel sender housing and fuel sender seal--Refer to Fuel Sender Assembly Replacement .

Did you find and correct the condition?

Go to Step 8

Go to Diagnostic Aids

6

Replace the fuel tank. Refer to Fuel Tank Replacement .

Did you complete the repair?

Go to Step 8

--

7

Replace the leaking fuel pipe. Refer to Fuel Hose/Pipes Assembly Replacement .

Did you complete the replacement?

Go to Step 8

--

8

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 2