Fuel Tank: Testing and Inspection

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 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
^ Movement of the EVAP pipes or fuel pipes may help find an intermittent condition.

TEST DESCRIPTION

Steps 1-8:

The numbers below refer to the step numbers on the diagnostic table.
1. Perform this procedure in order to determine that no EVAP diagnostic DTC is present.
3. This test is to locate fuel leakage in the fuel lines.
4. This tests for fuel leaks below the fuel tank fuel level.
5. This test is to locate fuel vapors escaping above the fuel level in the fuel tank.