PURGE VALVE and Charcoal canister

[gsxr]

@Ricardo, the purge valve can be bypassed if desired. It will not affect engine operation. The tank still vents into the canister, and the canister doesn't need replacement if the valve is bypassed. So, you can disable the purge system - for off-road/racing use only, of course. OTOH, if you keep the purge system intact, a new canister is probably a good idea - seems quite a few have ruptured screens/mesh/whatever that is supposed to keep the carbon from sneaking out under vacuum.

 

[gerryvz]

When you install your new charcoal canister, @RicardoD, it will be important to do it the @Jlaa way — make sure you wear gloves so as to avoid having fingerprints in the canister’s shiny black paint.

It would be grating to know that the “hidden” charcoal canister behind that NLA inner fender cladding has oily fingerprint smudges that mar its perfectly polished glossy surface.

Jlaa

 

[Jlaa]

OMG, please stop with the list of parts I must hoard / replace on my E500. My car runs great and who knows if my purge valve is working or what the inside of my charcoal canister looks like. I hope mild California climate means these bits last forever.

When you install your new charcoal canister, @RicardoD, it will be important to do it the @Jlaa way — make sure you wear gloves so as to avoid having fingerprints in the canister’s shiny black paint.

It would be grating to know that the “hidden” charcoal canister behind that NLA inner fender cladding has oily fingerprint smudges that mar its perfectly polished glossy surface.

Jlaa

Hmmmmm. To be fair when I replaced my cannister in 2021, I felt the finish wasn’t perfect, even though it was wrapped in bubble wrap, paper, and then cardboard box! See fisheyes on the end cap .

 

[gsxr]

Hmmmmm. To be fair when I replaced my cannister in 2021, I felt the finish wasn’t perfect, even though it was wrapped in bubble wrap, paper, and then cardboard box! See fisheyes on the end cap .

Please tell me you didn't install that eyesore, Jlaa! I assume you had it stripped & repainted with Sikkens or Glasurit, then handled with fabric gloves during installation, right?

 

[195910]

Reviving the charcoal canister discussion. I had a number of cars with EVAP system issues so I consider this system problematic and must be inspected on every car.

I can hear a clearly audible hissing sound coming from the charcoal canister of the C36 at idle, and it has the same frequency as the vent valve cycle. This does not occur all the time, I think its after filling fuel. I have not notice this on any other car!

No pressure/vacuum in the tank, no external fuel smell and the vent valve is operating correctly. Any suggestions? Could this be a symptom of a clogged canister?

 

[gsxr]

I can hear a clearly audible hissing sound coming from the charcoal canister of the C36 at idle...

No pressure/vacuum in the tank, no external fuel smell and the vent valve is operating correctly. Any suggestions? Could this be a symptom of a clogged canister?

I don't know how the W202 fuel tank venting system works, but if it's similar to the W210, there will never be significant pressure OR vacuum in the tank (unlike the 124 fuel tanks, which typically have pressure in the tank). Have you traced all the lines/hoses to check for leaks?

 

[195910]

I dont know how the W202 fuel tank venting system works, but if its similar to the W210, there will never be significant pressure OR vacuum in the tank (unlike the 124 fuel tanks, which typically have pressure in the tank). Have you traced all the lines/hoses to check for leaks?

Hi @gsxr ,

Yes there is no vacuum nor positive pressure in the tank, which I think is correct since these have a two part fuel tank.
I am not sure if this hissing sound coming from the charcoal canister is normal. My concern is if the PO had been topping up the fuel tank (like most people do) this could have flooded and clogged the charcoal canister, forcing the vent valve to constantly inject atmosphere air (i.e internal vacuum leak) rather than fuel vapor.

 

[French02chris]

So sorry... I realized that I never posted an update on my hard start issue!!!!!!!!!

It was actually a failing Camshaft position sensor!!!! When I replaced it, everything was back to normal
( a 10 minutes job.. Lol)

However, I still haven't replace the charcoal canister that I bought... I am replacing it this coming July (2023), as I will have some time to do it : hopefully it's easy to replace & don't need any special tools!!! Lol

 

[French02chris]

Took some time today to replaced my charcoal canister in a 93 degrees Florida weather.. Easy to take out, but more time to put it back!!!!!! Would not slide correctly..
The old one was bad (leaking bits of charcoal)

 

[Pat]

If anyone is interested in what the charcoal canister looks like, here are a few photos. Currently they are Mann branded, and are made in Bosnia-Herzegovenia.

Overview of the black-painted cylindrical filter canister:
View attachment 164160

End of the canister, with cover for the ports, as well as the MB name, part number and manufacturer:
View attachment 164161 View attachment 164162

Box and MB part label:
View attachment 164164 View attachment 164163

Thank you. My good son may have overfilled my '94 E420 and gas and charcoal bits are leaking near the canister location. Will the canister have to be replaced or is the canister able to release the gas and some charcoal bits and still perform after it has had a chance to dry out? I pulled off the hose from the canister at the purge valve and blew through it and heard bubbling and then only the hiss of my breath and the gas seemed to be expelled, but is the canister ruined now?

 

[Alphasud40]

The canister will dry out but if you are seeing charcoal pieces coming out of the vent lines those particles will clog the purge control valve. If it were my car I would install a fuel filter just ahead of the purge valve. The filter I’m thing about is a filter for a VW Beetle. That will prevent the valve from becoming clogged and visually give you an indicator of any debris being pulled from the canister.

Hengst 13321277497, H101WK Fuel Filter; 6/8mm Inline Filter

Find Hengst, H101WK Fuel Filter; 6/8mm Inline Filter 13321277497 at discount prices in our extensive auto parts catalog. AutohausAZ offers a large selection of Hengst parts online. Fits Audi, BMW, Porsche, VW. H101WK

www.autohausaz.com

 

[gsxr]

The canister will dry out but if you are seeing charcoal pieces coming out of the vent lines those particles will clog the purge control valve. If it were my car I would install a fuel filter just ahead of the purge valve. The filter I’m thing about is a filter for a VW Beetle. That will prevent the valve from becoming clogged and visually give you an indicator of any debris being pulled from the canister.

Hengst 13321277497, H101WK Fuel Filter; 6/8mm Inline Filter

Find Hengst, H101WK Fuel Filter; 6/8mm Inline Filter 13321277497 at discount prices in our extensive auto parts catalog. AutohausAZ offers a large selection of Hengst parts online. Fits Audi, BMW, Porsche, VW. H101WK

www.autohausaz.com

Fantastic idea, even with a new charcoal filter.

As an FYI - it wasn't mentioned in this thread, but has been discussed elsewhere - the purge valve & plumbing can be blocked off. The vapors in the carbon canister will be vented to atmosphere. All the purge valve does is ingest the vapors to be burned, instead of vented. Obviously the proper fix is a good purge valve and new carbon canister, but in a pinch, these can be bypassed/sealed without affecting engine operation/performance.

 

[Pat]

Appreciate the input. I did disconnect the purge line at the valve and put a plug on the suction side of the valve. No CEL yet and I don't think the computer will know it's being fooled. Probably do a new canister and maybe the VW filter later.

 

[Alphasud40]

You are correct your car does not have the ability to test the evap. emissions and as long as the purge valve is connected no fault codes will be generated.

 

[cole67]

I've had my purge valve prefilter (PVPF) mod installed for about 6 months. Works great but it's a band-aid and I need to get the new cannister installed. Check out the granules in the filter...doing its job. At least is saves me cleaning the PV constantly.

Coming up on 299K 0n the odo and she's running better then ever!

 

[Pat]

I want to replace the fossilized rubber hoses for the gas tank vent valve and return line, the vent pipe inside the tank is apparently open inside the tank at or near the top of the tank.

Does the fuel return line discharge at the top of the tank or the bottom of the tank? If it's at the bottom, replacing that rubber hose should be done with the tank at or near empty.

 

[gsxr]

Does the fuel return line discharge at the top of the tank or the bottom of the tank? If it's at the bottom, replacing that rubber hose should be done with the tank at or near empty.

The fuel return line is near the bottom, so you'll need to drain the tank so there's only a couple gallons left (at or below reserve level) to avoid a never-ending stream of gas once you disconnect the hose. (Don't ask how I learned this.)

 

[Pat]

Thank you gsxr.