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Discussion Starter #1
I was driving last saturday, and my CEL decided to turn on. I drove to Autozone and the code is P0455 (large EVAP leak). I replaced the fuel cap about a week ago, becuase it was throwing another code at me then (loose/defective fuel cap-I don't remember the DTC number). So, I am assuming I have a leak somewhere other than at the cap now.

This probably is related to why my gas tank leaks if I fill it up all the way. It only leaks if the tank is completely full---if I stop filling before the gas pump automatically shuts off, it is fine. This problem showed up after I replaced my fuel pump (I didn't know it was covered under the recall when I had replaced it). I guess I'll be dropping my tank to find the problem. Is there an easy way to find the leak?
 

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I have not had a Focus fuel tank off, but if fuel is overflowing somewhere when you fill it up "all the way," I suspect the leak will be obvious when you drop the tank, as it likely is a loose hose or clamp, or fuel pump seal. If you suspect the tank or fuel pump seal, you could plug any lines with rubber stoppers, spread some soapy water in like spots, and mildly pressurize the tank by blowing in it with a tight seal. I cannot recommend this, as there are carcenogenic warnings for gasoline; however, that's what I probably would do.
 

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Discussion Starter #3
I would think that the leak would be easy to find too, but I checked the tank right after filling it to see if I could see where it was leaking from and couldn't really see where it was from. The top and side of the tank seem wet, so I'm thinking it's the seal on top where the fuel pump goes in. I'm pretty sure it's not a loose hose because it should leak all the time if it was.
 

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"so I'm thinking it's the seal on top where the fuel pump goes in."

That would also be my first guess, since it usually makes sense to check the last work you did, and the fuel pump seal is a bit more difficult to seal than a hose with a clamp.

If you want to give something a try, you can dust a little foot powder up there before the next fill-up to help in showing prior "leak trails" when you drop the tank. They actually make some power spray for this purpose, but foot powder is cheap and, while it doesn't work as well, it might be of some help.
 
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