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Discussion Starter · #1 ·
So I am up to about 4000 miles now on my 2005 GT convertible after taking posession at the 900 mile mark and I am starting to get this "Check Fuel Door (or Cap...can't remember for sure)" warning. The only thing I ever did was change out to a locking gas cap ripping off the old one and the new locking one no longer has a tether but the original one was platic anyways so I doubt that could have affected things but who knows. I tried putting the old cap on but still got the warning but I did not put the tether back in place. Any ideas?

tc
 

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I have not seen the problem you've got, so take what I suggest as speculation.


The locking cap might have set a code in the computer because it didn't respond as expected to some check made for the emissions system. If the locking cap set a code, it needs to be cleared. Putting on the old cap might prevent the code from being set again, but won't erase the code already in there. I think. YMMV
 

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Yeah, it may take a few starts and stops to clear the Check Light after you put the old one back on... Possibly try disconneting the battery for a while.... My guess is the new gas cap isn't making a tight enough seal when it's on... You may want to try cleaning the rubber seal on the cap and wipe off the gas filler too...
 

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texascanuck said:
So I am up to about 4000 miles now on my 2005 GT convertible after taking posession at the 900 mile mark and I am starting to get this "Check Fuel Door (or Cap...can't remember for sure)" warning. The only thing I ever did was change out to a locking gas cap ripping off the old one and the new locking one no longer has a tether but the original one was platic anyways so I doubt that could have affected things but who knows. I tried putting the old cap on but still got the warning but I did not put the tether back in place. Any ideas?

tc
You may have a problem with the new cap not making a good pressure seal and the ECM detecting that.
 

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hey whered you get a locking cap, i want one

thanks
 

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Discussion Starter · #6 ·
Thing is I have had the locking gas cap on for a couple of weeks now and this only started 2 days ago and I have pushed the "System Check" before with the locking gas cap on and had no problems.
 

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texascanuck said:
Thing is I have had the locking gas cap on for a couple of weeks now and this only started 2 days ago and I have pushed the "System Check" before with the locking gas cap on and had no problems.
I'm unfamilar iwthe the "System Check"... I'm guessing eventually some where down the line the gas tank loses pressure so it triggers the warning... Had the same problem on my Porsche... bought it used and like 2 days later the CEL light comes on! I'm like OH SH*T! I cleaned the rubber seal on the cap really good and wiped the filler neck... Did the trick... CEL went off after a couple of stop/start cycles and never came back on...
 

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texascanuck said:
So I am up to about 4000 miles now on my 2005 GT convertible after taking posession at the 900 mile mark and I am starting to get this "Check Fuel Door (or Cap...can't remember for sure)" warning. The only thing I ever did was change out to a locking gas cap ripping off the old one and the new locking one no longer has a tether but the original one was platic anyways so I doubt that could have affected things but who knows. I tried putting the old cap on but still got the warning but I did not put the tether back in place. Any ideas?

tc
I know this may sound corny, but I drive a FORD RANGER for my job and the stock gas cap came loose from the plastic tether that held it in place. Although the cap was on tight, I got the idiot light showing the cap loose. Only when I put the tether back in place did I lose the idiot light, so I think it has to do with that connection. I don't know if there is a ground moulded within the plastic or not???

I tried to get the locking gas cap from my dealer that FORD lists as an accessory, but they say after much research it doesn't exist. Why would FORD show the accessory if it didn't? Seems kinda strange, and the vehicle warranty says that using a non FORD cap will violate the warranty on the fuel system completely.

Hmmm???

Manny
 

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I bought a Ford locking cap that included a tether from Kevin Casey, Parts Manager at Clevenger Ford 1-800-570-5554. He is great to deal with and has many items at good prices. He is a member of The Mustang Source Forums (05stangkc). BTW...pacific time zone if you try to call.

Fits perfect and no issues with sealing & throwing a check light.
 

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Discussion Starter · #10 ·
Well I put the original tethered cap back on including tethering it back to the fuel door and cycled on and off a few times the car but no dice, still reporting the "Check fuel cap" on the 2 line display. Everything is clean.

tc
PS: Thanks for the heads up about the Ford guy with the official one though
 

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Discussion Starter · #11 ·
Well everything is ok again.


I tried putting the old one back including tether and it still reported "Check Fuel Cap". I tried cycling the engine via a few start stops but no dice. I went away for the weekend and left it sitting. I came back Monday and no more "Check Fuel Cap". I then put back my locking gas cap and it's still good!

Baffling!

tc
PS: Oh and here's a tip, if you have trouble filling your tank like I did with it stopping multiple times, rotate the gas nozzle handle counterclockwise by about 45 degrees or so and damn that puppy fills up lickety split $43 worth - holy crap!!!
 

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Discussion Starter · #12 ·
Update - problem back!


Well, the Check Fuel Cap thing came back. I tried switching back to the regular cap again and leaving her sit but no dice. The thing comes on at start-up and then precisely every 10 minutes thereafter...drove me bananas on a road trip this past weekend to Mexico. I made an appointment at my dealership.

I dropped off the car yesterday and it turns out it needs a new fuel cap and more importantly had developed some leak of gas vapors in the fuel neck that they need to repair...guess that explains some of the suckier fuel mileage going down as low as 12mpg I have been having in the city (although highway was about 22-23mpg)...still there today...they were waiing on a part to come in today.

tc
 

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Discussion Starter · #13 ·
Conclusion:
Dealer changed out fuel cap and O-ring and no more warnings.

tc
PS: Man that Ford Ranger loaner truck sucked...but did make me re-appreciate the Stang when I got it back like 3 days later...just like the day I bought it!
 

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No one mentioned the biggest cause of this issue, and the reason we have this fuel cap specific light. Filling car while pumping.
Other models it would just set a Check Engine Light, now they got smart and for evap system problems they put a specific light in the dash so people wouldnt freak out at the Check Engine light.

.........Filler neck was leaking vapors, did they change anything with it besides an O-ring? Reason I ask is I had talked to a Ford mechanic and mentioned the gas fill issue, and he said it was related to "flappers" in the filler neck that were sticking.

Anyway, glad the problem was straightend out for you!
 
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