Buy a new gas cap.

 

Tried that, didn't help. Also, cleaned the filler neck area and made sure the cap was clean and free from debris.

 

And if you don't have any bad hose connections I would lean toward the sensor. Not sure where it is though. I would have to check my chilton's when I get home.

 

Have you backed into a parking spot recently and bumped a curb or anything?

 

That's what I've been looking through (Chilton's Manual), and I can't find anything in there about it. That's why I'm wondering if maybe it goes by some other name. The closest thing I can find is a Fuel Rail Pressure and Temperature Sensor, but I don't think that is the right sensor. It has me thinking that maybe it is part of the fuel pump assembly?

---------- Post added at 12:11 PM ---------- Previous post was at 12:06 PM ----------


I don't think so. The light first came on after driving to work, shutting off the car, going inside for about an hour or so, then coming back out and starting it up again. Came on immediately at start up. Every time I've reset it, it comes on after almost the exact same sequence. I can reset it, drive home (2mi), park it for the night, drive to work the next day (15-20mi), then the next time I start my car from work, the light comes on. Maybe I should quit going to work?

 

I had to replace seal on filler neck where it mounts to tank to get rid of mine

 

I believe it is mounted on the fuel tank. A little background...I fought this evap leak code for 2 years on my F150. Finally lowered the gas tank and found a pinhole in the gas tank on the top between the bed and cab. The hole was less than 1/8 inch. I must have dropped a rock down there hauling gravel which nicked the tank and rust, salt, etc. eventually formed a pinhole. Replaced the tank. To get the sensor out of a F150 you just rotate it about 1/4 turn counter clockwise and disconnect the 2 wire electrical connector. It has an o-ring seal to the tank.

There are also a crap load of evap hoses running to a charcoal canister and vacuum solenoids in that truck. I replaced all rubber hoses at that time and also tested and blew out the evap solenoid with air compressor and made sure it held.

All the reading on the net I did it works like this. At certain ambient temperature, during fuel level between 1/4 and 3/4, at steady cruise the pcm activates the solenoid vapor control valve. This causes a vacuum to be pulled on the fuel tank and associated plumbing from the intake vacuum. If this vacuum cannot be pulled to a certain pressure and held over a certain time by the vapor control valve the computer determines you have a vacuum leak in the fuel system and sets a code. For my 97 truck the side of the hole is calibrated to be no more than 0.040 inch and my 07 mustang is calibrated to a hole no more than 0.020 inch diameter.

Pros use a smoke machine to test for any leaks by pumping smoke into the fuel tank and inspecting for smoke exiting anywhere from the tank or plumbing.

Here is a good description link. Apparently on the mustang the sensor is above the fuel tank in the plumbing..

http://iihs.net/fsm/?dir=230&viewfile=Evaporative Emissions.pdf

 

Thanks Boomer. Well, I guess I'll have to drop the tank down a bit and see if I can find that sensor, or a hole. I'm thinking maybe I can just let it down enough to get a good look from the access covers under the rear seat. Just need to empty my gas tank now. I have a couple ideas on how to do that though...:3gears

 

Question…overfilling a gas tank…it affects in some way the functions of sensors??