Two things; first, check to make sure there is no light rust on the filler tube where the cap screws on. That can cause a small leak. Next, what I suggest is to have the system smoked to see if you can locate the leak. Smoke is injected into the evap system at a very low pressure. If there is a leak, the smoke will come out at that point.
Here are the directions for tank replacement. I'm giving these directions because they explain the removal and replacement procedure.
2005 Pontiac G6 V6-3.5L VIN 8
Fuel Tank Replacement
Vehicle Powertrain Management Fuel Delivery and Air Induction Fuel Tank Service and Repair Removal and Replacement Fuel Tank Replacement
FUEL TANK REPLACEMENT
FUEL TANK REPLACEMENT
1. Relieve the fuel system pressure. Refer to Fuel Pressure Relief Procedure.
2. Drain the fuel tank. Refer to Fuel Tank Draining Procedure.
3. Raise and support the vehicle. Refer to Vehicle Lifting.
4. Loosen the fuel filler pipe jumper hose clamp at the fuel tank (1).
5. Disconnect the fuel filler pipe jumper hose from the fuel tank.
6. Disconnect the vapor recirculation line that runs parallel to the fuel filler pipe jumper hose.
7. Release the exhaust pipe insulators from the underbody hangers.
8. Release the muffler insulator from the underbody hanger and slowly lower the exhaust to rest on a tall jack stand. If this is not possible, remove the rear half of the exhaust system at the take down flange.
9. Disconnect the fuel pump module harness electrical connector from the vehicle underbody wiring harness.
10. Disconnect the evaporative emissions (EVAP) vent valve solenoid harness electrical connector from the vehicle underbody wiring harness.
11. If applicable, disengage the antilock brake system (ABS) wiring harness from the retainer on the side of the EVAP canister.
12. Use an appropriate adjustable jack to support the fuel tank during removal.
13. Remove the front left hand (LH) fuel tank strap bolts and strap.
14. Remove the right hand (RH) tank strap bolts and strap.
15. Using the adjustable jack, lower the fuel tank slightly in order to access the fuel line connections.
16. Disconnect the fuel feed and purge lines at the fuel and brake line bundle on the right side of the vehicle.
17. Cap or plug the fuel tank feed and vapor return pipes to prevent fuel loss and/or contamination.
18. In order to clear the exhaust pipe, slowly lower the RH side of the fuel tank.
19. Once the tank is clear of the RH frame rail, remove the fuel tank down and forward toward the RH side of the vehicle.
20. If only the fuel tank is to be replaced, remove the fuel pump module assembly from the fuel tank.
1. If fuel tank replacement was necessary, install the fuel pump module assembly to the fuel tank.
2. Begin to install the LH side of the fuel tank over the exhaust pipe.
3. Raise the RH side of the fuel tank into position inboard of the RH frame rail. Use care in feeding the fuel feed, the EVAP vapor pipe, and the fuel pump module electrical harness over the exhaust system.
4. Remove the caps or plugs from the fuel tank feed and vapor return pipes.
5. Connect the fuel feed and vapor purge lines to the fuel and brake line bundle on the right side of the vehicle.
6. Fully raise and install the fuel tank into position.
7. Install the RH fuel tank strap and strap bolts.
8. Install the LH fuel tank strap and strap bolts.
NOTE: Refer to Fastener Notice in Service Precautions.
9. Tighten the fuel tank strap bolts.
Tighten the bolts to 20 N.M (15 lb ft).
10. Remove the adjustable jack from under the fuel tank.
11. If applicable, engage the ABS wiring harness to the retainer on the side of the EVAP canister.
12. Connect the EVAP vent valve solenoid harness electrical connector to the vehicle underbody wiring harness.
13. Raise the exhaust into position and install the muffler insulator to the underbody hanger.
14. Install the exhaust extension pipe insulators to the underbody hangers.
15. Connect the fuel pump module harness electrical connector to the vehicle underbody connector.
16. Connect the fuel filler pipe jumper hose to the fuel tank.
17. Tighten the fuel filler pipe jumper hose clamp (1) at the fuel tank.
Tighten the clamp to 4 N.M (35 lb in).
18. Connect vapor recirculation line that runs parallel to the fuel filler pipe jumper hose.
19. Lower the vehicle.
20. Refill the fuel tank.
21. Connect the negative battery cable.
22. Inspect for fuel leaks using the following procedure:
1. Turn ON the ignition, with the engine OFF for 2 seconds.
2. Turn OFF the ignition for 10 seconds.
3. Turn ON the ignition, with the engine OFF.
4. Inspect for leaks.
Let me know if this helps. Also, if you could let me know the code that was found, it may help me better diagnose the issue.
Images (Click to enlarge)
Tuesday, October 20th, 2020 AT 4:07 PM