How to test and repair your EVAP valve:

Post by **thecheat** » 04 Aug 2010, 15:17

I have adapted this from my original howto for the BMW M30 engines. They both use Bosch systems and the valve is identical. What happens is that at startup the valve stays open to draw fumes caught in the charcoal canister. The fumes are there because they evaporate from the fuel tank. This is why your gas cap is usually checked at emissions inspections and why the manual says you may have a temporary check engine light when you fill up with the car on. The only place evaporating gas can go is the charcoal canister which is then pulled into the intake at startup.

This is pretty much always the P0455 code.
http://www.obd-codes.com/p0455
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Here is how to test it according to the official service manual:

Get a 12v source with some alligator clips - I used a power supply for an external hard drive. It was 3 amps but you should be able to use 1 amp.

Get a vacuum source - preferably with a gauge on it. Attach it to the larger port on the valve.

Energize the valve with your 12v source, then pump the vacuum up. It should hold at least 50 milibar for 20 seconds. It probably won't. You don't need a vacuum gauge, just get a rubber squeeze bulb, squeeze it, and it ought to stay deflated. If it doesn't, you should fix or replace it.

You can also test the harness to make sure it isn't an electrical problem. The two pins ought to have 12 volts always when the car is running.

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What you need:

Tube of RTV. I used sensor safe Ultra Black but you can probably use anything, that's what I had on hand.

Thin blade flat head jeweler's screwdriver.

Some Q-tips.

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Here's how to fix it:

1. Open it up. This is a pain but if you take your time you should be fine. Get a jeweler's screwdriver and stick it between the seam of the valve. You will be breaking the glue seal so you need to use some force but don't get sloppy - just take your time and pry all around gradually.

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2. You will have two halves - one side has a little plastic thing that holds a spring against a rubber stopper. Not sure what this is supposed to do - maybe prevents backflow.

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The other side has the business end. This is the electromagnet that causes the valve to close. The coil energizes and pulls the flap in the middle closed.

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3. Pry it out gently. You will see there is an o-ring which is probably petrified. I suppose if you wanted to, you could find an o-ring that fits and use it instead of the RTV fix. I had RTV on hand an no o-ring so I went that route. You will still need to seal it back together with RTV but you don't have to glop it in to seal the bottom.

The slots are for using a screwdriver to adjust the gap for the flap (on the metal spring on the other side, don't mess with it).

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4. Get your RTV and Q-tips. Put a reasonable amount of RTV in the housing for the electromagnet. Don't forget to put some in down the inside of the hose barb but not too much that it might seal it shut.

I had tried to reassemble without the O-ring but it wasn't keeping a seal because there was too much empty space.

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5. Stick the electromagnet back in, you will see there is a cutout for the connector, it is in the bottom right on the picture above.

6. You can test now by applying a vacuum and 12v. It should hold vacuum.

. Reassemble the two halves, make sure the little rubber plunger thing works - just stick the jeweler's screwdriver in and you should feel it move.

7. Slather on some RTV around the seam and let it sit overnight.

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8. You're DONE!!!

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icelandic · Post by **icelandic** » 04 Aug 2010, 18:01

I understood the whole procedure and thanks for sharing. However, what did I miss? what causes the fault? The O-ring?

Sounds like a good project. I wonder what other problems a faulty valve may cause besides setting the code. Perhaps by not closing, it will let unmetered air into the intake causing the engine to run rich. Am I correct?

Icelandic

Post by **thecheat** » 04 Aug 2010, 19:07

Correct. What happens is the o-ring hardens and shrinks, allowing unmetered air from the charcoal canister to alter the air/fuel ratio. The fix seals the bottom half of the valve and keeps air from bypassing.

The mix will actually be lean. I was never able to get my E32 BMW's diagnostic system to work so I dont' know if it will set a code but it is a gigantic vacuum leak and your symptoms will be rough idle that goes away as you bring the revs up.

Post by **jreed** » 05 Aug 2010, 05:24

Beautiful investigation! Thanks for writing this up with pictures! I have cleaned out that valve with mineral spirits and tested it electrically a time or two trying to solve a P0455 code which ultimately turned out to be a squirrel-nibbled vacuum line at the roll over valve on my 97 855 GLT. But I never thought to open the valve itself up and clean it out. --> Will save this for future reference when the valve goes bad! What was the diameter and thickness of the o-ring?

icelandic · Post by **icelandic** » 05 Aug 2010, 06:26

Thanks again. The reason why I mentioned that the engine will run rich is that as the air coming thru the faulty valve is unmetered, the engine will tend to run lean. But the O2 sensors will pick that up and will tell the ecu to send more fuel thru the injectors to compensate. Maybe the engine will not actually run super rich, but mileage will drop. It is a shame that a system designed to prevent vapors from the tank to go into the atmosphere, will actually cause the engine to use much more fuel and cause more pollution due to a poor design of the valve. You may very well have found the solution to one of the mysteries in the 5 cyl volvo engine unexplained mileage drops.Bear in mind that the leakage in the valve does not go from 0 to 65 at once. It must develop over a long time, until the flow becomes so high that the ccorresponding code will be set.

Icelandic

Post by **jblackburn** » 05 Aug 2010, 08:13

Awesome, added to the repair database!

Thanks for the contribution, and I'll remember this if mine ever goes bad

peacock · Post by **peacock** » 05 Aug 2010, 12:35

Now if any one could ever figure out what causes p0453! i have the older evap valve and simply replaced it to get rid of the p0455 then again the older style only costs about $30

oakztiO2 · Post by **oakztiO2** » 11 Aug 2010, 03:29

where can i find the evap valve and how can i remove it from its position.. im sorry im new to this evap thing so i still dont know what to do..i am a DIYer myself amd i cant wait to try it myself. thanks in advance guys...

halpert2 · Post by **halpert2** » 14 Aug 2010, 22:38

I am trying to figure an easy way to fix my P0455 code. Gas cap did not work, so on to the next step. I did see this video on youtube and it might be helpful to oakxti02: First watch this
Then watch this one:
Hope this helps you.
I am no expert.

Post by **Red-Arrow** » 13 Dec 2010, 19:53

Nice repair, I found my purge valve was maybe leaking a touch of air soI used a hand pump to test it and it held 50psi but when I de-energized the purge valve it would allow the pumps plunger to collapse which means air got pasted the valve when it should have closed.

I used thick 5-w40 engine oil to seal the valve. I just poured it into the valve and energized it until the oil came out the other end with the help of some air. I also removed the check valve found above the fuel filter as it was jammed shut. I can't find this valve online. its only number is 04091, can I use any vapour check valve?