Suf_C230

Hello Everyone ;
Unfortunately I have the CEL recently with Code P0456 “ small Evaporation leak ". I’ve saw most of related threads , all seems to have the faulty filler neck due to many cases I’ve read with such problem.
I have changed the seal ring at the charcoal canister , although the old one was not damaged .now I'm suspecting the leak is in the filler neck , Really appreciate if anyone can give me the updated part number of the filler nick since some mentioned that old one have different Part # .

Appreciate your help .

91RS

Have you tried replacing the gas cap first? This is the usual cause of a leak.

The only way to really tell where an EVAP leak is coming from is to take it to a shop. They will hook up a smoke tester to the EVAP system and pump smoke into it and find where the smoke comes out.

Suf_C230

I have reset my CEL after installing the new Charcoal canister ring , next step will be the new gas cap , I have a feeling the CEL will return soon
I just wanna know the faulty part .
I've took it to the Dealer , they told me its the Charcoal canister , No smoke test was done by them ( I dont know if they have it here !), they only tested the valve purge & decided it is an faulty charcoal canister!

91RS

With a problem like this, it probably would have been best to pay them to fix it, too. Then you could have taken it back and raised hell and probably wouldn't have had to pay any more. Honestly, there's so many things it could be and there's no real way to just tell you what the problem is. Replace the gas cap and clear the code again. If it comes back it likely actually does have a leak somewhere and will have to be smoke tested to find it.

Suf_C230

I think you are right , I'll replace the cap & if it doesnt work I send it to the dealer & perform the smoke test , if they have it , thanks 91RS

Glyn M Ruck

The fuel filler pipe seems to have been faulty on a number of US cars. Perform smoke test.

drb930

You can take the Fuel Filler Neck out of the car, plug the extra hoses, and air and check it in a tank of water.

LILBENZ230

I called it in Maverick's thread and I think it's the same thing here - the filler neck.

Isn't it amazing that the dealer always fingers the purge valve and charcoal canister first? Always. It also always seems to be the 2005 cars - mine, Phil's, Mav's, your's, etc.

Dealer solution = no proper diagnosis, just throw parts at it.

Suf_C230

yeah Glyn it seems the filler nick is common issue with the w203

it will be the next step after changing the Gas Cap ( Just waiting the CEL ) , I hate this feeling .

You are right ! they only tested the purge valve & the conclusion was a faulty charcoal canister !

I have done 120 miles now since resetting my CEL , I suppose another 80 miles & it will appear again .

Suf_C230

I've got the filler neck part number from the dealer :

Old Part # : A 203 470 17 20
New updated one : A 203 470 19 20

it seems Mercedes modified the filler neck to more reliable version

I'll keep you updated , many thanks all for your help .

samaritrey

the strange thing is i have not seen any 01-04 car with this on here at least seems like 05 issue.

maverik259

haha ya took the dealer like 8 days to determine it was a valve near the fuel filler neck that was leaking and that was with after a smoke test on day 1 and after replacing 4 things including the charcoal canister and purge valve and after sending me home once. just take it to the dealership and tell them whats wrong and where you want them to look first. treat them as someone who you are hirering to do chores around the yard. They always do better with prior guidance lol...

vstarblack

My c230 has developed a fuel leak. The mechanic (not a dealer) says it is at the filler neck. He is saying the entire tank needs to be replace.
Is that the case?

LILBENZ230

A liquid fuel leak and an EECS leak are two different things. The filler neck can be replaced separately of the tank.

vstarblack

Matt, thanks. do you know where I can find a diagram of this fuel tank assembly?

Suf_C230

hi again ;
problem not solved yet
I've changed the fuel cap ( CEL after 120 miles ), charcoal canister O ring ( CEL after 120 miles ), Purge valve ( CEL after 1k miles! )
unfortunately no smog test available at this part of the world , even at MB dealer !!!
three parts in my mind , Charcoal canister , filler neck & fuel level sender unit . what should I start with to get rid of this P0456 " very small evaporation leak " ?
any way to cancel the EVAP system sensors test using STAR without loosing the CEL function ?! ( sounds weired but this CEL drives me crazy !!!)

appreciate your feedback , have a great day .

LILBENZ230

Why didn't you replace the fuel filler neck FIRST? That's the problem with your car. Throwing parts at it.. just like a dealer. Sigh.

Suf_C230

believe me I don’t wanna through parts at my car , just paid over 35k $ for it on Dec 2009 , along with local customs & tax’s .
car alone was ~ 18k $ , with 31k miles at it .the funny thing that I found the car 1st owner total payment receipt , 34,999$ / 2005! , it was registered in CA.
my CEL started at 37k miles , currently my car total mileage is 44k miles .since the car was imported , I have to wait three weeks each time I order a part .
I really like c230 style , specially the AMG kit & its power , all C class cars here are c180 or c200 , same M271 engine but with less power, smaller brakes & rims ..etc.

It’s a bad feeling that you expect to have your CEL on each time you start the car ! so I guess I;ll star with the filler neck , hope it will solve it. thanks for the advice .

Suf_C230

I was thinking , why did CEL went off for 1000 miles after changing the purge valve , although average time to trigger CEL On was around 120 miles .
if the filler nick pipes are faulty , shouldn't I get the CEL after 120 mile as will ?
could it be the fuel pressure sender unit faulty and keeps the purge valve always on till it burns or get faulty ? noting that I never hear hissing noise when opening my fuel cap to fill fuel .

so is the fuel presser sender unit responsible for Purge valve function alone ? or its combined with the pressor sensor readings at the charcoal canister ?

Glyn , any idea ?

LILBENZ230

It's the fuel filler neck.

Glyn M Ruck

There are no easy answers to the EECS problem. I would replace the filler neck with the new part. This only seems to afflict post facelift cars.

What fuel pressure sender unit. Fuel pressure regulator is integral with the filter.

Here's the diagram someone wanted

Suf_C230

thanks Glyn for your reply .

I mean part #120 at the fuel tank . 1st pic .

you've mentioned the fuel pressure regulator is integrated with the fuel filter , I had my CEL on after almost 3000 km from srvice B , the dealer changed my fuel filter , could it be the reason for the CEL ??
fuel filter part number ( from the dealers Invoice :A002 477 30 01
could a faulty fuel filter regulator triggers the CEL ?
any differance between fuel filters at the c180/c200 with M271 engines & my c230 ? I'm sure they've used same c180/c200 fuel filters .
thanks again .

LILBENZ230

Why must this be difficult? The fuel filler neck issues affect solely the 2005 cars in the experience on the board. It has affected many of us with 05s. Just like you, several of us had dealers throw purge valves and charcoal canisters at the problem. When the dealer threw those parts at my car the CEL stayed off for days before returning.

Your problem is very, very likely the fuel filler neck. If you want to continue to throw parts at it, it's your money to waste.

Suf_C230

Hi Matt ; please take it easy
I'll replace the filler neck first as you adviced .
Just wanna double check if I am in the right way , & not a previous changed part is causing all the troubles .

thanks again & have a great day

Glyn M Ruck

Part #120 is the fuel level sensor - left.

All filters are the same apart from later M272 V6 engines.

There is no fuel pressure sensor. You have to use a gauge on the injector fuel rail.

The filter cannot trigger a CEL unless it clogs & the car throws a fuel trim code - lean!