I think I may know what the noise is coming from and where the small leak is. For fuel to enter the fuel tank, air has to be able to escape. If you craw under the vehicle where the fuel filler tube is located, you will see a smaller hose that runs along side of the filler tube. That is the breather. If it is plugged or damaged, air can't escape. As a result, the fuel backs up in the filler tube and shuts the fuel pump off. It's a pain. If there is a humming noise, that could be coming from a leak from the breather when pressure us produced in the fuel tank.
Check that and let me know what you find. As far as finding a small leak, by eye, you could look for weeks. There is, however, an easy way to find it. You need to have the system fogged. Fog is actually pumped into the EVAP system at a very low pressure (I think 1psi). The fog will come out where the leak is located. That is my recommendation if the breather is good. Also, I'm surprised your mechanic didn't recommend that.
One last thing. I understand the engine light is on again. Is it only for the EVAP leak or is the O2 sensor code still showing?
Let me know.
Saturday, August 14th, 2010 AT 10:38 PM