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My teenage son has a 2014 Mustang that we bought used and has about 56K miles on it. A month or so after buying it, a warning came on about the fuel door. Checked it, cleaned it per youtube videos, and cleared the code and all was good. Then the CEL came on with a code about the evaporative system. We replaced the purge valve as that seemed to be the simpliest thing to do and cleared the light.

CEL came back on. Cleared it a few times with FORSCAN and it keeps coming back. We had a buddy who owns a shop do a smoke test and smoke was coming out of the fuel filler neck and the capless fill area. I ordered a new filler neck from RockAuto - Spectra FN736. We were planning to install it this weekend and take it out of the package and find that I can push the flap down with my finger. My son was like "dad, you shouldn't be able to do that". I was like "your right", you have to use the FORD funnel to push the flap down on his Mustang and on my 2014 F150 (BTW, I have had my truck since new and it has 78k miles on it and no issues with the fuel filler and we use it in some dusty places when we go ATV riding.)

I called Spectra and they said part is defective. Back it goes to RockAuto. Now we have to wait on the replacement to arrive.

In the meantime, I am wondering if the earlier 2010 - 13 Mustangs had to have the funnel or a fuel filler to push down the flap or was that a 2014 enhancement. I am wondering if the replacement Spectra Part will have the same issue as the part is made for 2010 to 2014 Mustangs. Maybe (hopefully), I just got a defective part.

Finally, I am wondering if the locking fuel plug may fix the problem. Anyone have any experience with that helping?

Just like the red gas cans that we use to fill our mowers and other toys, I spill more gas now due to the mandate government venting system than I ever did with the old style cans. This whole system on the new cars around venting and purging is a failure just waiting to happen and what was freaking wrong with a screw on gas cap to begin with? Previously, I had to replace a gas cap on a car for about $10 because the seal failed now I have to take the drivers rear of the car apart to replace the filler neck for over $100!

 

They are the same, neither my old 2010 or my 2013 Mustang open without the Funnel and neither does my 2013 F150.

 

WD-40 and the funnel fixed mine. It took more effort than the videos implied, but it worked.

 

I basically used the same technique as SpectreH, ie. I shoved the funnel in and out of the filler often and rapidly after squirting some WD 40 into it. I also used compressed air in the opening while doing so. No more problem. I like the capless system [ when it's working ] since lost gas caps are no longer an issue, but I agree it is a high tech solution to a low tech problem.

 

Done the funnel, WD40, other cleaners and compressed air numerous times to no avail. It is a flawed design that should really be rectified by Ford.

As stated no issues with my truck with more miles but if evaporative loss is such an issue for the EPA, then why not just use a cap with a rubber seal vs this capless system. But I am old school and prefer my cars and bikes with out all of the sensors and computers that just go bad.