GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 4WD 🢒 Engine 🢒 Engine Controls - 4.3L 🢒 Fuel Tank Leak Test

Fuel Tank Leak Test Pickup

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 two test cycles.

Diagnostic Aids
    • Operate the vehicle under the condition of the customers concern. During 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.
    • Test for fuel leaking in the following locations:
       - The fuel tank
       - 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 fuel fill pipe, hose and fuel fill cap
       - The fuel sender housing and seal
       - The fuel tank pressure (FTP) sensor seal
       - The EVAP vapor pipe
    • Moving the EVAP pipes or the fuel pipes may help to locate an intermittent condition.

Test Description

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

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

  2. This test is to locate fuel leakage in the fuel lines.

    3.

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

    4.

  4. This test is to locate 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

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 the fuel pipes for damage or for 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 you locate a fuel leak from the fuel pipes?

Go to Step 8

Go to Step 4

4

  1. Install the J 41415-40 Fuel Tank Cap Adaptor.
  2. Connect the J 41413 EVAP Pressure/Purge Diagnostic Station to the fuel tank cap adaptor.
  3. Command the EVAP vent valve ON with a scan tool
  4. With the EVAP pressure/purge diagnostic station, pressurize the fuel tank.

Did you locate a fuel leak from the fuel tank?

Go to Step 7

Go to Step 5

5

  1. With the EVAP pressure/purge diagnostic station, maintain pressure in the fuel tank.

    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, 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 Level Sensor Replacement .
    • The fuel tank pressure (FTP) sensor seal--Refer to Fuel Tank Pressure Sensor Replacement .
    • The fuel fill pipe and hose--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 repair?

System OK

--

8

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

Did you complete the replacement?

System OK

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