GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2002 🢒 Envoy - 4WD 🢒 Engine 🢒 Engine Controls - 4.2L 🢒 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 customer's concern. Under high temperature conditions the 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.

Test Description

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

  1. Perform this procedure to determine that no EVAP diagnostic trouble code (DTC) is present.

  2. This test locates fuel leakage in the fuel pipes.

    3.

  3. This tests for fuel leaks below the fuel tank fuel level.

    4.

  4. This test locates fuel vapors escaping above the fuel level in the fuel tank .

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

Caution: 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. 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 7

Go to Step 3

3

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

Did fuel leak from the fuel pipes?

Go to Step 8

Go to Step 4

4

  1. Turn OFF the ignition.
  2. Install the J 41415-40 Fuel Tank Cap Adapter.
  3. Connect the J 41413 EVAP Pressure and Purge Station to the fuel tank cap adapter.
  4. Turn ON the ignition, with the engine OFF.
  5. Seal the EVAP system with a scan tool.

    6. Important : DO NOT exceed 15 in. H2O.

  6. Pressurize the fuel tank with the J 41413 .

Did fuel leak from the fuel tank?

Go to Step 7

Go to Step 5

5

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

    2. Important: The fuel tank may need to be partially lowered. 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, the fill limiter vent valve, the pressure relief valve, and the rollover valves--Refer to Fuel Tank Replacement .
    • The fuel sender housing and fuel sender seal--Refer to Fuel Sender Assembly Replacement .
    • The FTP sensor seal--Refer to Fuel Tank Pressure Sensor Replacement .
    • The fuel fill pipe, the fuel fill hose, and the fuel fill cap--Refer to Fuel Tank Filler Hose Replacement .

Did you locate a fuel or vapor leak?

Go to Step 6

Go to Diagnostic Aids

6

Repair the system as necessary.

Did you complete the repair?

System OK

--

7

Replace the fuel tank. Refer to Fuel Tank Replacement .

Did you complete the replacement?

System OK

--

8

Replace the leaking fuel pipe. Refer to Fuel Hoses/Pipes Replacement - Filter to Tank .

Did you complete the replacement?

System OK

--