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Discussion Starter · #1 ·
Hello everyone, friday as I was filling the tank in my 2005 mustang v6 4.0 automatic, I noticed that it left a puddle of fuel. I checked and didnt see any punctures in the tank or anything of that sort, also checked after driving it and no more leaks. Today I went to put more gas on it just to check and sure enough, leakage occurred near the fuel tank. I cant seem so see it leak any other time other than when pumping fuel to it, and I am not overfilling it. While driving back home, the light on the dashboard to check fuel cap came on, checked it and it is properly sealed. Also I am not loosing fuel while driving, I mean its not using an excessive amount of fuel, just uses what it normally used a week ago and so. Any thoughts? Anyone has had this happened to them before?

Also, check engine light is on, tomorrow I will have a mechanic connect it so he can tell me what code it is reading.

Thanks for your help.
 

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If you already had the leak before you replaced the fuel pump, you might want to check the area where the filler neck joins the tank. Otherwise check the fuel pump area and make sure it's properly installed with a good seal.
 

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Discussion Starter · #3 ·
Thank you Bullitt95, I didnt have the leak before, I changed the pump on Thursday, come Friday the leak started. Now Ive been keeping an eye on the fuel levels and right when I stop the car to check for leaks; nothing leaks. Only when filling the tank at the gas station, and the tank doesnt have any holes or anything. Im thinking it could be the seal from the filler neck that goes into the tank? Maybe the whole filler neck?
 

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Since the leak was not there before the pump was replaced, that is the most likely culprit.

There was a large green o-ring seal between the tank and fuel pump hat. Was that put back in place?
Also, the ring that holds the pump hat into place must catch ALL teeth when it is put back in, and you need to drive it into place using a hammer and punch or screwdriver to get the ring all the way locked in, which will push the pump down against the seal.

You need to find where the leak is coming from.

Are you getting a "fuel cap" error or is it just that the engine light is on? Makes a difference. If the pump hat is not sealed, you'll get the effects of a loose gas cap, so the pump not being installed properly is still the most likely cause. (The evap system uses engine vacuum to test the integrity of the closed fuel tank vapor system, and if the vacuum cannot be held, the PCM indicates an error. A vacuum would not be held if the fuel filler cap is off or bad, or if the pump is not seated properly, or if there is some other issue in that emissions crap under the trunk.)
 

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Since the leak was not there before the pump was replaced, that is the most likely culprit.

There was a large green o-ring seal between the tank and fuel pump hat. Was that put back in place?
Also, the ring that holds the pump hat into place must catch ALL teeth when it is put back in, and you need to drive it into place using a hammer and punch or screwdriver to get the ring all the way locked in, which will push the pump down against the seal.
x2 on what he said.
 

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Discussion Starter · #6 ·
Guys thanks for the help I really appreciate it. The loose cap light is also on. So that might be the problem. I'll check it and let you know how it went. Once again, thank you for your time and help.
 

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Guys thanks for the help I really appreciate it. The loose cap light is also on. So that might be the problem. I'll check it and let you know how it went. Once again, thank you for your time and help.
We're glad to help. Some things on these cars are a little tricky, other things are pretty simple. But, issues do come up, and knowing what to do can save you a lot of time and money, and prevent other issues.
:salute:
 
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