Well I got the chance to take the seat out and take the inspection covers off today. I didn't notice anything but the car was at a quarter of a take. I went and filled it up and here is what I found after driving 10 miles.



If you look to the upper right you can see where the black plastic (which I'm guessing is part of the tank ) is getting wet with fuel. You can also see where the fuel is sitting in the base of the unit to the inside on the right side, which is the low part of the unit due to the way it sits.



Camera angled back to get a better view of the tank.



View of the pool of gas on unit on the rear side. It looks like its leaking from that plastic piece on the left side of the photo which I'm guessing is the sending unit. This could be the cause of the whole problem. Hard to tell if its 2 pieces or not but it looks like theres a seal there.



Just another shot of the above with better lighting.

Now until today I never smelt gas on the inside of the cab. I'm hoping it's only due to the fact the covers where off. I have smelt it on the outside after filling up. I also noticed that while driving and moving air was coming thru the inspection holes while moving. So if a sufficent amount of fuel leaked there is the possibility of the fuel running down the tank to where ever.

I had the SBC Pump replaced on 28 June and mentioned to the SA that I smelt fuel after filling it up. I have the print of the leak test which says it passed. Guess I'll have to show him the photos.

 

I took the car to the dealer and had it looked out, got good info to post up.

They diagnosed fuel sending unit and will be replacing it and the fuel pump at no charge (whew!) Parts alone are $1100 and with labor would be over $1500.

The tech and service manager say that if it is the unit then gas will be on top of it as many pictures in other posts clearly show. The car will smell of gas after filling up. If the problem is the evaporator hose issue then the car will throw CEL code and smell like gas. They had a few tanks to be discarded and I got a couple pictures.

First pic shows the hole where the sending unit goes and where the seal to the evaporator hole connects. It is the white(ish) nozzle to the right of the unit hole. Remember the unit is under the drivers side and the pump is under the passenger side.

The next picture is the seal that leaks if your problem is the evaporator hose connection. This thing would be under the middle of the rear seat and can not be seen directly with the eye. Apparently techs use a light and mirror to see the seal and along with whether the car is throwing codes, diagnose the issue. If this seal is bad then the tank has to be replaced.

They say that since the tank is under pressure that if its the seal leak it will loose fuel pressure and throw the CEL code. Of course a car could have both problems at the same time but they seem to put a lot of emphasis on the codes or not. The sending unit in my car had fuel on the top and around where it fits into the tank so I thought I may have had both issues, tech said probably not. I never saw him use a mirror and I looked under the cover before taking it in so I'm not quite sure how they use a mirror and light but whatever. The codes or no codes makes sense.

Also talked about if this issue is due to ethanol, probably so but do not use any additive like is used in marine application.

Apparently the design of the fuel sending unit has been updated too. I will take a picture of it after its fixed.

 

IMHO the tank will leak again. It may take 6 months...it may take 12 months but it will leak again.

The only real fix is to replace everything...tank, senders, fill tube and all hardware.

I went thru 5 sending units and even more seals in 3 years before MB finally replaced everything. Been fine since.

If you have any info on updated sending units please post the source. Is the pn different? What build date is updated?

I do not see how a vapor pressure leak inside the tank would change the fuel pressure at all. The fuel pumps and regulator are sealed and the bypass just dumps into the tank.

What an awesome thread. 12 pages and over 14,000 page views. Nice job MB.

 

211-470-51-94 sending unit DS
211-771-05-79 same # for seal.

Had this replaced back in march 2011.

 

It sucks that this is even happening and for so many years now is rediculous.

Was your car giving codes?

 

no codes, just gas vapors every time i filled up. Would last until a 1/4 tank went down and fumes went away. It started happening when i had an 9month old in the back seat and didnt want him to breathe it in.

 

Thats very similar to mine. Our girl just turned one on the 23rd.

Have you had trouble with it since then?

 

Since the repair, no issues so far.

 

This seems to be the "real" fix (and as I mentioned in a previous post here.) I was in today to see my dealer for some unrelated service and had a quick chat about the issue. The initial "fixes" were not solving anything (as you well know) but a tank replacement along with everything else is doing the trick. One reason why dealers hesitate doing the tank is because of the labor involved (sub frame drop.) And getting the labor charge rebated from MBUSA isn't as easy as they'd like. So a lot will depend on one's relationship with their dealer. btw, he said the parts aren't new but have been "adapted" for the issue (whatever that really means.)

What's unusual is that not all cars will develop the issue. They've seen W211s with high mileage and no problems, and the population with issues is relatively small compared to all registered W211s on the road. It's almost like luck of the draw.

But here's a good one: my dealership said they just did a fuel sending unit fix on a leaking car the other day...... the car: a W212.

 

You have got to be kidding- a new model same issue

Now that you mention "adapter," I remember that is exactly what my tech said about the new unit.

The service manager mentioned that there is a high cost of disposing the tanks too. They cant just throw them in the dumpster, some one has to come by and pick them up for disposal. The pictures that I got were from 2 that were lying outside for 6 months he said.

Anyway, I am dropping the car tomorrow morning for replacement so I will update as we go

 

What if you just don't fill the tank all the way up?? That should alleviate the majority of the problem.... right?

 

You mean treat the symptom , NOT the cause. Makes no sense to me

I guess you could do that pending repair, BUT I would certainly hope that IF you had the problem, you'd get it fixed.

Anyone know the cost if MB does not step up and pay the parts and/or labor?? I've seen $3000 plus??

 

yup i have heard this, i think mb usa not taking this seriously

 

I talked to a tech that I know. He works for the dealer that did the sending unit campaign on my 04 E55. He's going to talk to his service manager about replacing whatever needs to be done on my vehicle since they preformed the work and he knows that I take good care of the car. He would hate to see it burn up.

 

same thing just happened to me yesterday i got the smell.. i checked under the inspection cover to find a pool of gas. i was driving on the highway right after i filled up only to about a quarter tank. mercedes says they wont fix it. i dont know if i was part of the recall in 2008 because i just bought the car last year. but it is listed under the hood on the recall campaign sticker. im pissed. any suggestions as to what i should replace??

 

The car is fixed and no gas smell. They even left a full tank of gas in it. Here are the part numbers.

211-470-36-94 Auxiliary PU I guess this is the fuel pump
211-470-38-94 Sender Unit
211-471-05-79 Seal ring (x2)

Thats a different number than you have for the sender unit.

 

How much $$$$ did this come out to?

 

The dealer covered it for me.

I used the information from this forum to talk to the service manager. I took the approach of that I knew they could not just fix stuff without going through proper channels. I relayed to them that I knew there was a recall on the sending units for earlier model years and that my car seemed like it was doing the same thing. I took it to them for verification, the tech opened the cover and saw fuel, no CEL codes and supposedly checked the seal at the evaporator inlet. SM agreed to replace fuel pump and sending unit on the spot. They had to order parts, offered me a loaner which I declined and took the car home to sit in my garage until parts came in. I took it back, got the loaner for the day and picked up my car after work.

And to boot, they even had a full tank of gas in for me.

 

Well, new fuel sending unit in place but the fuel gauge was not reading properly. I put a few hundred miles on it and noticed the gauge still over 3/4 tank. Filled it and it took 10.25 gallons.

Back to the dealer today, said the unit was bad and replaced it again, and I got another full tank of gas

This is crazy

 

2005 E55 - Stock, 55k Miles

Hopefully I can get some help.....

Recap of what's been done so far (see below)... As well, the dealer is now stumped. The only thing they can come up with is the type of fuel I use (Costco) may have additives that are causing excess pressure to build in conjunction with the Arizona heat???? MB noted to use Shell and or Chevron. Just filled up with Chevron, I'll see how this goes. Any HELP would be greatly appricated!!!

What's been done so far:
- Pressure test tank, both via Star and smoke test (both negative)
- Both fuel pumps are great, no leaks or signs of leaking
- New charcoal canister via MB dealer (free as this was not the problem), canister was "soaked" with fuel per tech.
- Smell comes when tank is any any level, but when it's hot outside and lots of stop and go driving.
- Smell comes from passenger side wheel well and in the cabin
- No puddles or any sign of fuel anywhere only the smell of it

 

Never top off a Mercedes, if your canister was soaked you are over filling the tank. Your canister is most likely soaked again and as the tank heats durring the day and the air in the tank expands, it vents through the gas "soaked" canister producing the smell.

When fueling, stop when it clicks off the first time, do not put any more fuel in. This is very very common and yes the canister is in the pass wheel well.
I am surprised the dealer did not tell you how canisters become soaked, speaks volumes as to their lack of expertise.

 

Agreed. I've never topped off. That's the strange thing, the smell happens at all levels i.e. full or 1/4 tank. As well,it could smell after a fuel fill up or a week later. The only common piece is the outside temp being hot.

 

I have the same exact issue. Leaking from the little plastic part of the unit.. I just ordered a new unit.

 

How funny that on the main page of the forum, you have the recall for diesels where the fuel filter is failing and causing leaks. But wont acknowledge this on the W211 where its happening as well.

 

What year cars or how old are they?