FAQ: Subaru EVAP Purge Control Solenoid Valve Information for EJ255 and EJ257 Motors

[IA Performance]

After receiving quite a few questions regarding the EVAP Purge Solenoid hose routing we figured it best to start a FAQ thread dedicated to the ej255 and ej257 applications.

Note: We are learning more about the system along the way so please bear with us as we aren't experts in this field. Thanks goes out to Dave at Rallispec for assistance along the way.

General EVAP FAQs
What is EVAP
Evaporative Emission Control System

What is the function of an EVAP System?
I tried to make this as short as possible: The EVAP system was designed to decrease fuel vapors as a source of pollutant. You see, gasoline vapors contain hydrocarbons. These hydrocarbons mix with air and sunlight to create smog, a pollutant. To curtail the smog output the car's gas tank vent's the fuel vapors, via the vent tube, to the charcoal canister, which serves as a temporary holding tank. So what's inside of a charcoal canister? You guessed it, charcoal. This activated charcoal absorbs the vapors and holds them until the car is fully warmed and driving. At this point, the ECU sends a few signals out. One, to the charcoal purge alerting it to open, as well as one to the EVAP purge solenoid, alerting it to open under vacuum. The vapors are then drawn from the charcoal canister, by vacuum, into the intake manifold, where they are ultimately burned up.

For a more in depth description we suggest doing a internet search. There are several good sources out there. *

Subaru WRX, STi, Forester, Legacy, Outback, and Baja ej255 and ej257 motor Specific FAQs
Is the EVAP Solenoid Open or Closed when at rest (no power)?
Closed

Is there a specific flow direction for the EVAP purge solenoid?
Through research, it appears the direction does not matter since the solenoid is simply creating an open or closed path for which the vapors to flow. When open, air can pass either way through the solenoid. Although, we still recommend following the diagrams for your specific model.

Is there a specific flow direction for the purge valve?
The Purge Valve (round black thing) is direction specific and should have an arrow painted on the front of it. For direction please take note to diagram A.
For some ej255 and ej257 models the round/black purge valve is still present, diag B. Whereas, some newer models replaced the valve with a second solenoid, diag C.

Which hose goes where?
Please see the diagrams below for your specific models. This area is work in progress so feel free to send us a PM with any information you may have that would help grow this post. Example: I do not see my 2013 Sti listed, but it is the same as Diag C (this would be helpful).

Note, if you have a 2.0L turbo motor please refer to our EVAP purge FAQ for ej205 turbo models here.

WRX
2006 = Diag B
2007 = Diag C
2008 =
2009 =
2010 =
2011 =
2012 =
2013 =

STi
2004-06 = Diag B
2007 = Diag C
2008 = Diag C
2009 = Diag C
2010 = Diag C
2011 = Diag C
2012 = Diag C
2013 = Diag C

Forester
info to follow

Baja
info to follow

Legacy / Outback
info to follow







It looks like spaghetti, can I decrease the EVAP clutter?
Yes, you can install the purge control solenoid without the use of the Purge Valve on the Diag B setups. A perfect example of a EVAP system that does not require the Purge Valve is the JDM Subaru ej207. This model still uses the same EVAP purge solenoid, but the mess of hoses is cleaned up considerably (only 2 hoses now). Diagram A and B cars can be setup in the identical fashion, although it does not apply to diagram C cars. There does not appear to be an affect on performance, nor does it trigger a CEL. In short, all it takes to run the EVAP purge solenoid is the valve, 2 hoses, and 2 hose caps to block off the unused nipples. Disclaimer: We do not know how this affects pollutant levels.


Do I need to be concerned with leaks (vacuum as well as pressure)?
Yes, a pressure, as well as vacuum, leak can have a great affect on the way the car performs. A vacuum leak will allow non metered air into the intake manifold, which creates a lean condition when the intake tract is in vacuum. As the car builds positive pressure (PSI) it will then allow air form the intake tract to escape through this leak. Since the ECU is unaware of this leak it continues to add the same amount of fuel, which leads to a rich condition during positive manifold pressure conditions (full throttle is especially affected).

We suggest using zip ties at any hose connection on the intake manifold, EVAP system, as well as turbo inlet tube. P.S. don't forget to do the same for the Fuel Pressure Regulator hose

Below are the most common EVAP related leaks that we've run across that will affect the performance of the ej255/7 motors:
1) The junction of hoses at the blue 'T' connector, located behind the P/S pump. As the hoses dry out they become lose and come apart. Plus, the T connector does not have barbs on the nipples to help keep the hoses on.

2) The next most common leak area is the ~1" long, straight, hose going from the intake manifold to the Purge Valve. Since there are no hose barbs at either end of this hose it can easily come off the manifold and/or Purge Valve. As a rule of thumb, any hose nipple should have a barbed end on a boosted motor. If this hose is lose we suggest replacing it with a new one. Just about any vacuum line will do, assuming it has the same ID.

3) One of the more expensive leaks is created when one of the EVAP Purge Solenoid nipples is broken off. This seems to happen the most when people [cough] carelessly install an aftermarket turbo inlet tube. If this happens do NOT glue it back together. Rather, spend the $100+ and replace the unit with a new one from Subaru. There are way too many negative side affects with a broken valve (pollution, loss of power, etc). Be extra careful with cars that have 2 solenoids since this could lead to twice as many expensive parts to replace.





*rabech27 contributed the following on 9/18/2014:
The charcoal you refer to is actually activated carbon pellets. I worked at the only plant in the world that can make the grade of carbon that goes into those canisters. Mead Westvaco is the company that makes it and their plant is located in Covington, Virginia. I worked there as an engineer for three years. It is made with sawdust and phosphoric acid, heated in a large rotary kiln (100 ft long), then shaped into pellets, and run through another kiln that activates it and creates the adsorption characteristics that hold the fuel vapors. The activated carbon has millions of pores that hold the fuel vapor molecules until the purge system opens and purges the vapors off the carbon. Just thought I'd share that with you in case you were interested.

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This is great info!

[Andrewxxcarlson]

Exactly what I've been wonderin!

[danger1138]

Will zip tie the connections at the blue tee as soon as i het home.

[Mark2JZ]

under what conditions does the solenoid open? just wondering. startup only? or anytime the engine is under vac?

[IA Performance]

Read the 2nd FAQ

[SnprSlick]

What direction does the EVAP valve flow? I don't see Diag A like there was on the other one.

[IA Performance]

I'm not sure I understand the question. Valve = Solenoid? The fuel vapors flow from the back of the car ultimately up to the EVAP solenoid and into the manifold. It is a solenoid that opens and closes, flow direction should not really matter.

STephen

[SnprSlick]

Originally Posted by IA Performance

I'm not sure I understand the question. Valve = Solenoid? The fuel vapors flow from the back of the car ultimately up to the EVAP solenoid and into the manifold. It is a solenoid that opens and closes, flow direction should not really matter.

STephen

I mean the round thing with all the vacuum lines. The one that comes off the intake manifold. The thing has an arrow on top and it goes one way or another. Which way does the arrow need to point? Toward the EVAP or toward the turbo inlet?

"EVAP Purge Valve"

"Is there a specific flow direction for the purge valve?
The Purge Valve (round black thing) is direction specific and should have an arrow painted on the front of it. For direction please take note to diagram A.
For some ej255 and ej257 models the round/black purge valve is still present, diag B. Whereas, some newer models replaced the valve with a second solenoid, diag C."

[IA Performance]

Arrow points towards turbo inlet duct

[Wes-MotoIQ]

Thanks for posting this up! I am working on our project 08 STi and am considering ditching the lower purge valve and only running the upper as posted.

Has anyone with a USDM GR ran this setup and if so was there any CEL associated? The lower does have a harness connection so not quite sure on that.

[gtasti]

Great info but not understanding where vent return under manifold line C goes can u explain that a little more I've been wanting to remove all the crap long time ago thank you

[Wes-MotoIQ]

Originally Posted by gtasti

Great info but not understanding where vent return under manifold line C goes can u explain that a little more I've been wanting to remove all the crap long time ago thank you

There is a hard line connected to the fuel lines and it terminates just below the purge valve and slightly under the IM.

[Wes-MotoIQ]

And disregard the question on the GR. I decided to leave both in place as the GR does nto have the secondary valve and uses a second electronic valve. I am curious as to if both of the valves see the same values and operate at the same time, if so one could possibly delete one of them and just tee the wires from one valve in to the other... At this stage I will leave them alone but might play around with it in the future.

[gtasti]

Originally Posted by Wes-MotoIQ

There is a hard line connected to the fuel lines and it terminates just below the purge valve and slightly under the IM.

I don't have the stock fuel lines any more

I'm thinking this would be the return vent line from the gas tank correct ? If that's the case then I just need a striaght fitting to connect the lines together

[Wes-MotoIQ]

Originally Posted by gtasti

I don't have the stock fuel lines any more

I'm thinking this would be the return vent line from the gas tank correct ? If that's the case then I just need a striaght fitting to connect the lines together

Exactly right! The line that is on the firewall between the fuel supply and return. Essentially it just routes to the hard lines as you know.

Hope that helped.

[gtasti]

Ok great thanks that's what I figured which line it was

[gtasti]

So I removed that thing had to go back to re scale my injectors turns out I had a boost leak most likely from that stupid thing good thing I had to go back

[sexyyrex]

Easiest way to delete this system?

[cbazq271]

I have a 05 sti, which has the style (B) set-up. What is the purpose of having two "venting" valves. The purge control solenoid and the purge valve. I would like to remove the purge valve, but I don't understand the relationship between the two valve/vents.

[Josh LaCroix]

I recently purchased an JDM Spec C intake manifold, which I believe is mated an EJ207 over in the promised land. Earlier in the thread, you said that the EJ207 doesn't have the purge valve, and that our EVAP systems could be setup similarly.

However! In the pictures I've seen of the intake manifold, it does still have the one nipple on the front that points down, while the smaller nipple for the purge valve is indeed absent. According to the diagrams, this downward nipple towards the middle was also connected to the purge valve...do you think they had a solenoid that shut closed when manifold pressure was positive, and it hooked up directly to that nipple? I can't think of any other reason why they'd leave it on the manifold.

I will probably cap this one or hook up my boost gauge to it, and run the solenoid directly to the turbo inlet.

edit: oh, and the manifold is going on a custom STI engine that is using my '02 WRX's, uh, oem 'infrastructure,' so for the sake of argument, this is perhaps considered an EJ205 application.

[IA Performance]

To our knowledge the version 7 and 8 intake manifolds should both have a hose setup like this:

http://i115.photobucket.com/albums/n...purge_edit.jpg

The purge valve (round black thing) is omitted. Sti and Spec C, for each year, should all be the same intake manifold as well. I.E. Spec C is no different than STi for Version 8.

Stephen
www.facebook.com/iaperformance

[Josh LaCroix]

Ah, that would make things much prettier. So just to be sure, the EVAP can be connected directly to the intake manifold without the purge valve? And it knows to close so that boost pressure isn't being sent back to the charcoal canister?

edit: Sorry, answered my own question in the first post, only opens under vacuum

[Speedster329]

will deleting the purge valve solenoid affect anything with power or mainly just deal with emmission?

is there a way to delete this to not have it all connected up on the front of the intake manifold ?

[IA Performance]

Speedster329 - Alternative to moving the solenoid, you can move the solenoid to a different location in the engine bay. We've seen where customers remove this valve completely, but we do not take that approach since we'd prefer to keep the EVAP system working.

Stephen
www.facebook.com/iaperformance