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evap leak - replace charcoal canister?


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17 replies to this topic

#1 ravenclaw

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Posted 05 April 2012 - 12:41 PM

I have a 2007 Subaru Forester with almost 61,000 miles. The check engine light has come on several times over the past several months. The dealership says the code (P0442) indicates an evap leak. They first suggested a new gas cap. This didn't fix the problem.

Yesterday I took it to the dealership and they did a smoke test to see where it might be leaking. The first issue that came up was the charcoal canister. They said there was liquid fuel in it (from me topping off the gas tank) and I need a new canister ($481.85) and then they will re-test to see if it leaking anywhere else.

My question is if this is really needed or not. If I stop topping off the gas tank, will the canister dry out and be OK? I am really suspicious of dealerships....it seems like most of them try to gouge you for as much money as they can. The service guy said I could wait a little while to replace the canister but if I wait too long other things could be damaged.

Any thoughts or suggestions about any of this?

#2 ocei77

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Posted 05 April 2012 - 03:33 PM

Salvage?
05-07 are the same.
1stsubaruparts, lists for $255 plus 10% shipping.

I would personally remove unit and rig something to blow warm air through it to get rid of as much accumlaled fuel as possible.or, even just leaving it out in the sun.

Unless I am wrong(someone will correct me if so) its only a charcoal canister.
http://opposedforces...parts/forester/

According to Opposed forces there are two types of canisters for the 07. Later production of Nov on is a different type

O.

Attached Files


Edited by ocei77, 05 April 2012 - 03:35 PM.
add


#3 Caboobaroo

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Posted 05 April 2012 - 05:35 PM

Check your fuel filler neck to see if its rusted out. A small hole in the filler neck can cause a P0442 code. Basically the fuel system isn't pressurizing up fully which is kicking the code on.

If you take off the passenger side rear wheel, you'll be able to get decent access to the filler neck to inspect it.

#4 the3rsss

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Posted 05 April 2012 - 06:09 PM

If you top off constantly, you probably did soak the charcoal canister. It can't purge thru liquid. Disconnect all the hoses to it and run it for a week. Might get a strong gas odor as it dries out. You won't ruin anything else with that code.

#5 lmdew

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Posted 05 April 2012 - 06:29 PM

I think you are new enough it might be covered under Emissions. Free is better but you may have to push it. Do some research and go with data.

#6 jamesm113

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Posted 05 April 2012 - 07:54 PM

You can try leaving it out in the sun

#7 mattocs

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Posted 05 April 2012 - 08:06 PM

Run a cheap fish tank air pump into it for a few days. That should dry it out and the pump, tubing, and some fittings would cost less than $10.

I've never done that... but it sounds like it should work.

Good luck!

#8 ShawnW

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Posted 06 April 2012 - 12:25 AM

Lots of short trips? Id take it for an hour plus long drive and clear the codes.
Oh, and stop when the pump shuts off. You would be amazed at the amount of emissions created by everyone in the world doing that and how much gas is wasted by that.

http://www.epa.gov/donttopoff/

#9 ravenclaw

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Posted 06 April 2012 - 11:38 AM

Thanks for all the suggestions! You guys are great!

I'll stop topping off my tank and I'll take out the canister and set it outside in the sun (weather is supposed to be nice this weekend). Hopefully this will help.

I will get another canister if needed, but I'm not convinced that this is needed yet. The same dealership also hinted that I could use a new set of tires (and I just got a high-quality set of new tires last November).

I'm thankful that I have some things to try first.

Thanks again!!

#10 jamesm113

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Posted 06 April 2012 - 11:59 AM

So a P0442 code typically means there is a small (under 0.04") leak in your EVAP system.

A little bit of background:
Your EVAP system works to contain all fuel vapors and preventing them from going into the atmosphere. The charcoal canister stores fuel vapors for the engine to be burned off later in the engine.

There are 3 hoses connected to the canister:
1. PURGE - Leads to a purge solenoid near the throttle body (mine was under the intake manifold). This solenoid is connected to the throttle body, and when open, draws a vacuum on the whole system, sucking fuel vapors out of the canister for clean burning
2. VENT - this allows clean air to enter the system, which is needed to displace gas that you burn. There is also a solenoid controlling this hose, called the vent solenoid.
3. CHARGE - this line connects to the top of the gas tank and is where the fuel vapors come from

When you are driving under a certain set of conditions (don't remember the exact specs, but it's something like 15-85% fuel, under 3000 RPM, steady speed under 75, higher than 45, and the car has been warm for over 8 minutes), the ECM starts a EVAP self test - it opens the PURGE solenoid, which starts pulling a vacuum on the system, and closes the VENT solenoid, which seals of the system.

It then monitors the fuel tank pressure sensor to see if:
A. there is a drop in pressure
B. the drop in pressure is held

If either of those conditions fail on two consecutive drive cycles, you will get CEL and the associated code.

If your canister is clogged, this could potentially prevent a vacuum from being pulled on the fuel tank. However, I would think this would cause a P0440 (.04" and over), rather than a P0442 since a plugged canister would prevent a lot of vacuum from being formed, rather than just a little.

Did your dealer say they found no leaks? Or they need to replace the canister before knowing if there's a leak or not?

Either way, leaving it out in the sun should dry out the liquid fuel

#11 ravenclaw

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Posted 09 April 2012 - 01:02 PM

Did your dealer say they found no leaks? Or they need to replace the canister before knowing if there's a leak or not?

Either way, leaving it out in the sun should dry out the liquid fuel



They said there is a diagram that they follow. The charcoal canister was the first thing they came to that had an issue (the liquid fuel in it). They say I need a new canister (almost $500) and then they will need to continue on the diagram to see if there is anything else wrong. Which makes me kinda nervous.

I am going to let the canister sit out in the sun and give it a little more time to dry out. Then I'll probably take it to another dealer or an independent mechanic and see what they say.

Thanks for all the information!

#12 edrach

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Posted 09 April 2012 - 03:06 PM

Give it time; I've had a p0440 cel on my '97 Impreza that's been with me for over two years. I've replaced most everything except the metal inlet pipe which is the next item on my list. The code doesn't seem to harm the engine or the driveability. When I finally get a fix, I'll post what did it for me.

#13 jamesm113

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Posted 09 April 2012 - 03:36 PM

edrach, have you tested the purge and vent solenoids using the green connector under the dash? Can you pull a vacuum on the system with a hand vacuum pump?

#14 edrach

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Posted 09 April 2012 - 09:17 PM

edrach, have you tested the purge and vent solenoids using the green connector under the dash? Can you pull a vacuum on the system with a hand vacuum pump?

No, not something I'm aware of.

#15 jamesm113

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Posted 12 April 2012 - 11:44 AM

Ok, underneath the steering drivers side dash, there are two green connectors. Connect them, and turn the IGN to On. You will hear every solenoid, relay in the car turning on and off.

Check the following solenoids by feeling them with your finger. If you can feel a click, they (and the wiring to them) are most likely good.
Purge control solenoid (under intake manifold, passenger side)
Vent solenoid (right by the charcoal canister)
Pressure control solenoid (front passenger corner of fuel tank)

#16 ravenclaw

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Posted 13 April 2012 - 11:40 AM

The other day, I noticed my check engine light is not on anymore. My cruise light would also flash and that has also stopped.

I thought this would only go away if the code was manually cleared. If you ignore it long enough, does the CEL eventually turn itself off? This is probably the longest I have gone without getting the code cleared out (I would say 2 or 3 weeks).

#17 jamesm113

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Posted 13 April 2012 - 11:42 AM

It will only go off if the issue has been resolved. Looks like you fixed it :)

#18 SnatchedHatch

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Posted 02 October 2014 - 05:09 AM

Hi, digging this thread up, you seemed to be very knowledgeable on this subject!
I recently popped a CEL with code P0453. It signifies the EVAP pressure sensor detected high pressure in the system.
I have a 98 EJ2w OBS, any idea what could cause that?

I bought a new fuel cap, and then today by chance, found the fuel filler neck while inspecting my rear brakes.
I took off a plastic cover to get to it, and found one rubber hose kinked it seems something is a miss as I see two new hose clamps, and the application of a few zip ties in this area.

I readjusted the suspected culprit and applied an additional hose clamp to unkink it.
Today I'll see how she runs, have to get my emissions done within 2 days.

Any advice is greatly appreciated, thanks!
-Sam

 

EDIT: Passed my emissions test the following day (today), no CEL.

I'll up date with pictures of the hoses near the fuel filler neck in question.

 

So a P0442 code typically means there is a small (under 0.04") leak in your EVAP system.

A little bit of background:
Your EVAP system works to contain all fuel vapors and preventing them from going into the atmosphere. The charcoal canister stores fuel vapors for the engine to be burned off later in the engine.

There are 3 hoses connected to the canister:
1. PURGE - Leads to a purge solenoid near the throttle body (mine was under the intake manifold). This solenoid is connected to the throttle body, and when open, draws a vacuum on the whole system, sucking fuel vapors out of the canister for clean burning
2. VENT - this allows clean air to enter the system, which is needed to displace gas that you burn. There is also a solenoid controlling this hose, called the vent solenoid.
3. CHARGE - this line connects to the top of the gas tank and is where the fuel vapors come from

When you are driving under a certain set of conditions (don't remember the exact specs, but it's something like 15-85% fuel, under 3000 RPM, steady speed under 75, higher than 45, and the car has been warm for over 8 minutes), the ECM starts a EVAP self test - it opens the PURGE solenoid, which starts pulling a vacuum on the system, and closes the VENT solenoid, which seals of the system.

It then monitors the fuel tank pressure sensor to see if:
A. there is a drop in pressure
B. the drop in pressure is held

If either of those conditions fail on two consecutive drive cycles, you will get CEL and the associated code.

If your canister is clogged, this could potentially prevent a vacuum from being pulled on the fuel tank. However, I would think this would cause a P0440 (.04" and over), rather than a P0442 since a plugged canister would prevent a lot of vacuum from being formed, rather than just a little.

Did your dealer say they found no leaks? Or they need to replace the canister before knowing if there's a leak or not?

Either way, leaving it out in the sun should dry out the liquid fuel


Edited by SnatchedHatch, 02 October 2014 - 08:11 PM.





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