Fuel Tank: Testing and Inspection

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, if more than the calibrated amount, when the evaporative emission (EVAP) diagnostics complete one test cycle. The malfunction indicator lamp (MIL) will illuminate after the EVAP diagnostics have failed two test cycles.

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.

Test Description

Step 1 - Step 7:

Step 8:

The numbers below refer to the step numbers on the diagnostic table.
4. This step tests for fuel leaks below the fuel tank fuel level.
5. This step tests for fuel vapors escaping above the fuel level in the fuel tank.