evap leak

[heathmo]

This has been an ongoing problem for me. I've had the Check Engine light come on and go off more times than I care to count now. At first it seemed as though it was only when the humidity was high outside and when it was nice the light would not come on or would shut off. Now that the weather has cooled off and the humidity has dropped significantly it's still coming on and shutting off randomly. When I was under there replacing the shocks I noticed that I might have been missing a hose on the evap canister. The box located above the spare tire and there is a spout end with a labeling on the box that says "to fuel canister" or something like that. Not sure if that's what's been causing my problem but I have tried adding grease to the gas cap and I've replaced it twice, once with a Stant locking gas cap then with a Motorcraft one. I don't live in the best area so I feel it's best to have the locking gas cap. Please give me any ideas - I'm tired of seeing that light on my dash. I know I still have to fix my ABS, but I know what's wrong with that at least.

 

[heathmo]

bump

 

[swetrid]

What code do you get?

 

[heathmo]

The code that AutoZone told me was a small evap leak - saying it's most likely the gas cap.

 

[swetrid]

If it was code P0442, it would probably be the canister vent solenoid in the canister above the spare tire.

 

[heathmo]

Can a regular code reader pick that up for me, like one that AutoZone would have? I know my dad has a reader too. I know that there's no way they're the Ford readers, but would that at least give me the code number?

 

[RomeovilleIL]

The best way to find an evap leak is a smoke test. Garages vary anywhere from $25 to $150 for this test so call around.

I'm not saying for sure this is your problem, but I've seen it on a couple trucks where we got stumped by these codes. It is possible to be caused by rust holes in gas filler tube pipe. The rust will be under the tank hose right at the clamp on the bottom side of the pipe. You cannot generally see it but you may smell gas when you stand by the back left wheel well.

It gives you on/off evap leak depending on flexing of the vehicle and subsequent slight changes in the position of the hose/pipe. The location of the connection is directly behind the rear left tire, just above and outside the frame. It gets wet, dirty, salty on a regular basis and wicks the moisture down between the hose and pipe. You need to remove the filler spout (4 screws around the gas cap) and then disconnect the two hose clamps to remove. It's quick and easy with the tire off to give you some room but you can do it with tire on as well.

If it turns out to be the filler pipe, it's not a cheap part. You can usually wire brush the rust off and reconnect the hose with some sealer like indian head or rtv and reclamp a little farther up the pipe past any holes. Not a perfect fix, but gets rid of the evap leak and stops water from getting in again.

 

[Bill MacLeod]

I had evap problems with my 99 this past winter/spring. Drove me crazy trying to find the problem. Turned out to be small cracks/holes in the plastic liner in the fuel fill pipe. (gas cap screws to this)
I had to remove the fuel filler pipe to actually see the holes. Little epoxy and know more code.
Take a good look at the grey plastic liner inside the fill pipe.