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06 XS MT
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13 Posts
Discussion Starter · #1 ·
Hello everyone, I looking for a bit of help tracking down the culprit of “small EVAP leak” code that I keep getting. Here is a list of what I’ve done so far:

- Changed fuel cap
- Changed fuel filler neck
- Confirmed operation of purge vavle
- Had a smoke test done (no leaks found)

At this point I’m running out of ideas and can’t just keep throwing money at this code by replacing random parts, does anyone have any suggestions of where to go from here? A couple of ideas I have left are:

- Take it to another shop for a smoke test and hope they find it
- The vent solenoid isn’t working (I can’t seem to find it on my car? Does anyone know where it is? I don’t hear clicking by the charcoal canister when the car is in test mode)
- Purchase an OEM gas cap since I just have a generic one
- Gas tank pressure test


Thanks for your time!
 

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05 Forester XS Manual
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311 Posts
Following... my forester has a similar issue. Changing my gas cap helped a bit... also need to sort it out.
 

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06 XS MT
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13 Posts
Discussion Starter · #3 ·
Honestly if it wasn’t for the loss of cruise control I’d just deal with it. Going to get a vacuum pump and see if I can narrow down the leak.
 

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2012 Forester 4 speed auto
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1,128 Posts
The vent solenoid is usually next to the charcoal canister. The solenoid is usually in the open position but must completely close to pass the evap monitor. Typically insects and debris keep the vent from closing so clean it out. Be very careful because vapors are highly flammable.
 

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06 XS MT
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13 Posts
Discussion Starter · #6 ·
Alright guys help me out here. So I spent a couple hours getting to know the EVAP system and taking off the charcoal canister. I believe the 2006 has a vent valve built into the canister correct? Can anyone tell me how I can bench test this? I don’t wanna be replacing the 300$ canister on a whim here since it holds vacuum just fine.

Also I discovered another solenoid above the canister, I believe this is just a pressure control and the cable feeding into it is just to send information as there’s no mechanical valve inside?

Finally is it possible to buy just the vent valve and put it into the canister?

I’ll grab some pictures of everything tomorrow morning.

Thanks!
 

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06 XS MT
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13 Posts
Discussion Starter · #7 ·


Alright guys, anyone got information on how to bench test part 9? What should it be doing? Is there a valve that should open/close when in test mode?
 

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2007 2.5 X AT 4EAT
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8 Posts
I had a broken connection on my vent solenoid, replacing it fixed part of the problem but the CEL would still come back.
After using SEAFOAM in the gas tank and brake vacuum line, the CEL went away for 1,000 miles so far
 

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06 XS MT
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13 Posts
Discussion Starter · #11 ·


Does it look like this? Cause that’s all I have above mine and it’s listed as the pressure solenoid.
 

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2007 2.5 X AT 4EAT
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8 Posts
yes, you should be able to blow air thru when open, no air when closed. The problem with the old valves is that "gunk" can get inside and coat the inside of the valve and it won't "fully" close. So after I changed my valve, I had a smaller leak from the other old valves in the emission system. I could tell it was getting better because the time between CEL was longer. So I tried cleaning my emission lines with Berryman B-12 (no difference) and then SEAFOAM. After the first bottle of SEAFOAM in the gas tank, the CEL didn't come back for 200 miles. When it came back, another bottle stretched the CEL to 600 miles. Third bottle and I am up to 1000+ miles. So far the SEAFOAM is working for me.
 

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2007 FXT Limited 5 Speed Manual
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186 Posts
yes, you should be able to blow air thru when open, no air when closed. The problem with the old valves is that "gunk" can get inside and coat the inside of the valve and it won't "fully" close. So after I changed my valve, I had a smaller leak from the other old valves in the emission system. I could tell it was getting better because the time between CEL was longer. So I tried cleaning my emission lines with Berryman B-12 (no difference) and then SEAFOAM. After the first bottle of SEAFOAM in the gas tank, the CEL didn't come back for 200 miles. When it came back, another bottle stretched the CEL to 600 miles. Third bottle and I am up to 1000+ miles. So far the SEAFOAM is working for me.
Hmmm...multiple applications of cleaner to the tank and it prolonged it each time... Mine spit out the P4220 small leak code and I already had a brand new Subaru Cap, so I cleaned the mating surface and gasket of the cap. Then added some Marvel Mystery Oil to the tank and had a small trip out of town, but the CEL flashed again when I was almost home, but this time the code was the P0456 very small leak. Each time my CEL triggers it is when I am driving on the open road. I can drive in town and it will never come on, but a few hours of highway driving and it triggers. I need to dig around like @Ski-Free is doing just to verify the status of things, but I am wondering if mine just needs some more cleaner ran through it like you did.

I have heard from Jackie that 2007's, and I am guessing it might include '06 thru '08, that the canister is an issue with these models. The vent valve is part of the canister too. I don't know it is just XT models or if it across the board. I didn't ask her that because mine is the on the problem-child-list when it comes to canisters.

Once in a while I can smell gas fumes, and other times I cannot. Like earlier this week, gas vapors were present when I was downwind of the car, now they're not. When I could smell them the tank was near 1/4, now it is full. I want to drive it on the open road to see if the CEL will come back but right now it is parked for the upcoming timing belt replacement. While it's down I need to also inspect the filler neck and canister area.

I will be following this thread to chime in on what I find and to see if you were able to fix yours. I have emissions testing in June 2019 and I need to make sure this issue is fixed for good.
 

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06 XS MT
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13 Posts
Discussion Starter · #16 ·
The CEL only comes on after the ECU runs two EVAP systems test and they fail. For it to run them there are specific conditions that need to be met that are usually favourbale to highway driving so that’s why you’re seeing the CEL only come on when on the freeway.

Anyone have experience changing out the vent valve inside the canister? It’s pretty easy to get at but I don’t understand how it works or where to get a replacement.

Maybe some more seafoam for now...
 

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2007 2.5 X AT 4EAT
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8 Posts
Mine had the intermittent gas smell also. Had to change the fuel tank vent valve to get rid of the smell on my forester, it's on top of the gas tank, was accessible from the back under the carpet.
 

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06 XS MT
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13 Posts
Discussion Starter · #18 ·
I may have gotten somewhere. I took the purge control valve off and it appears the bottom “outlet” will hold 21 in/mg of vacuum but the top “outlet” slowly leaks out vacuum pressure. Is this normal? I’m assuming not.
 

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2012 Forester 4 speed auto
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1,128 Posts
The purge control valve is normally closed. That is, w/o electricity the valve is closed. No air should be able to enter or exit the valve. Energizing the solenoid should open the valve.
 

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06 XS MT
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13 Posts
Discussion Starter · #20 ·
I replaced the valve, now I’m getting a P0549 Canister Purge Valve High Voltage code now. Any idea how to troubleshoot? I’m thinking it’s a short somewhere.
 
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