# EVAP Purge Valve (N80): Double checking function



## Vanagon Nut (Oct 19, 2007)

Hi all.
I'm double checking the EVAP system so need to understand more about the EVAP canister purge reg. valve.
EVAP is early model type. No LDP. 
Valve on engine and spare one test at 45 ohms.
At plug for valve: Ign. on: 12.xx Volts. Engine running: 14.xx Volts.
Seems ok. So...
12v connected to valve, it closes. Air can't be sucked through hose that connects to TB.
12V disconnected, not sucking hard, some air passes and I hear the valve kind of warble.
So when I first start the engine (cold), this valve should be closed right?
Under what general conditions should this valve cycle on/off?
Many thanks,
Neil.


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## Vanagon Nut (Oct 19, 2007)

*Re: EVAP Purge Valve (N80): Double checking function (Vanagon Nut)*

Bump
Simpler version
Should the canister purge valve close or open when 12V applied?
Thanks!


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## Eric D (Feb 16, 1999)

*Re: EVAP Purge Valve (N80): Double checking function (Vanagon Nut)*

I do have a spare purge valve on my desk, but I'm not going out to the Garage to get a meter to test it.
In this link I post how to clean the inlet screen. The screen becomes carbon fouled and blocks air flow.
Its not a documented fix, people just replace the valve and call it a day. I on the other hand like to know why something fails. So I investigated this and found the fouled screen.
Easy to fix, info in the link.
http://forums.vwvortex.com/zerothread?id=4323872
Years ago I was surprised at the cost of an ABS controller for a B5 Passat. We were replacing many of them a month at a cost of $1200.
I took a bad controller home, popped the cover off and found the problem. One could fix it for just a few bucks. I couldn't share this info because of liability reasons. But others had posted the same thing I found.


_Modified by Eric D at 9:39 PM 10-27-2009_


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## Vanagon Nut (Oct 19, 2007)

*Re: EVAP Purge Valve (Eric D)*

Much thanks Eric D
Didn't think to check out the 2.8 forum or search under Mk4. Stands to reason this type of valve is used on other later model V-dubs.
I'll check out my spare one (that seems hinky) and see if I can't pop it apart.
No power applied, both the spare valve and one on engine allow a little air to move through when sucking lightly on TB end of hose. They each make a "warble" type of sound.


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## Eric D (Feb 16, 1999)

*Re: EVAP Purge Valve (Vanagon Nut)*

You just need to pull out the screen, nothing else is done to the valve. 
The screen when fouled prevents air flow.
Its just a solenoid, engaged and disengaged. Screen filters out the particulates, and combined with moisture blocks the screen.
I used Berryman B12 Carb cleaner as it is very potent, and gets the job done.


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## Vanagon Nut (Oct 19, 2007)

*Re: EVAP Purge Valve (Eric D)*

(looks closer at pic)
Right. I see. 
Be interesting to see if the filter is clogged.
Curious why I can suck air through when solenoid isn't active, but when 12V applied, it shuts tighter than a ducks arse.
Thanks for pointer to carb cleaner
http://www.berrymanproducts.co...d=138


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## Eric D (Feb 16, 1999)

*Re: EVAP Purge Valve (Vanagon Nut)*

The two halves are sonically welded, so it can't be taken apart without destroying the plastic.
On OBD2 vehicles one can run an output test using a vag-com or similar tool. This is the how one tests the valves operation.
On my spare, with no power applied, I can not blow air in either direction.
Only when activated does it allow air to pass, this is normal operation.



_Modified by Eric D at 11:47 PM 10-27-2009_


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## Vanagon Nut (Oct 19, 2007)

*Re: EVAP Purge Valve (Eric D)*

That makes sense. (welded plastic) Looking at it I figured taking it apart would destroy it. Still, I may cut open the gerfunktabooten valve for research purposes. (since it closed when power applied)
Outstanding. Thanks for taking time to test your spare.







That helps diagnose a possible related EVAP issue on Vanagon "side" of the ABA swap. 
Valve should be open when voltage applied. Makes sense. 
Likely my purge valve has been closed too much of the time 
Neil.


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