2012 merc amg

The 2018 S560 I bought a couple months ago obviously has a fuel vapor leak back at the fuel tank. Complained to the dealer service about it 3 times now and they can't seem to find anything wrong, but it is there. There are no check engine lights no codes which I just checked for personally and it shows on the scanner evap active. So I'm pretty sure the EVAP system has not been bypassed or anything. When it makes the strong fuel smell is sometimes when I first open the drivers door in the morning. I suspect opening the door must be triggering a EVAP system test and the vapors are being pumped out of a leaking hose or seal or pump. It seems even more of stronger fuel smell when the tank is lower on fuel, like under a half tank. The fuel cap looks good, no gasoline spots under the car and the tank seems dry around the outside, obviously it is just Vapors. Does not seem to do it when the car is just sitting there. Only when I open the drivers door to get in the car. Maybe a leak on the topside of the tank? Question is though why would this not be tripping a check engine light and throwing a code, fuel smell is definitely coming from the backside of the car seems like the fuel filler side. Maybe fuel fill going to the tank? There again if this were the case why not a code? Looks like it's going to have to go back to the dealer a 4th time or maybe another dealer this time that is a bit more detailed in trying to solve this ongoing issue.

chassis

Typical Mercedes dealer behavior. These organizations are among the worst in the industry. Unfortunately.

Could it be a leak from the fuel tank fittings? Does it seem to be coming from the rear passenger seat area inside the vehicle? User @39039 posted two videos on a repair he did to an E-Class for a fuel leak inside the cabin. The fix also applied to C-Class years. Could a related problem also affect the S-Class? Parts like fuel tank connections/fittings are either common, or use a similar design across models.

2012 merc amg

There are no signs of raw fuel leakage I can see and the dealer claims they checked for that very carefully. I can go out the garage in the morning sometimes and no gasoline smell at all. Then I open the drivers door and I hear a hissing sound coming from the rear (originally I thought it was the suspension) and after that I smell a very strong gasoline vapor smell especially around the back of the car towards the passenger side. My theory is that opening the door must trip the EVAP self test and pressurize the fuel tank and EVAP lines and it is then that it is leaking the gasoline vapors. If that is not the case that opening the door trips a self test, well then I must be loosing my mind. The only cars parked in the garage are this car and my 2019 E class wagon and no other things such as power equipment or gas cans. Some days I don't notice any smell. It's really starting to seem like maybe the fuel tank needs to be dropped and the seals and lines all checked. I guess a smoke test may not do much for this type of issue if it is in fact leaking on something hidden on the top side of the tank. I sure would think the dealer might be able to tell from some type of pressure test to make sure a pressure needle is not dropping indicating a leak. At my old business we use to use pump up gauges that fastened onto where the gas cap goes into the tank. You'd pump it up and see if the pressure gauge needle dropped. If so there was a leak in the system. The same tool had a spot where you could put the gas cap on the tester and pump it up and test it for proper seal. With this type of issue I'd sure think I'd be getting a check engine light if it's leaking, strange.

39039

chassis is right. I don't trust the MB dealer after many of disappointing experiences. Check it yourself, and tell them how to fix it if your W222 still under the warranty.

2012 merc amg

Thats the reason I took the scanner to the car today but proved no codes either current or stored. I cant see anything wrong visually nor can the dealer. The next closest dealer is about an hour and half away. Hate to go that far away but I guess I might have too if I want this issue fixed. The car still has 4 more years left of factory warrantee, when I bought the car I got the extra 2 year extension of factory CPO MB warrantee, the car still has nearly 2 years of the factory 4 year 50K mile warranty. the car only has 19K miles on it.

39039

That's great. Hope you can fix the issue.
here are the videos chassis mentioned, hope them useful to you.

2012 merc amg

Thanks for the suggestion. The fuel filter housing is in a different much more easy spot to access on the W222. Here's a video on changing the filter. I would have hoped the dealer removed this access panel underneath the car near the exhaust to check the fuel filter housing but who knows, at least the backseat does not have to come out. The more I think about it this could be the source, it would not cause a check engine light as does the evap system (at least it's suppose to if it malfunctions). I think I've gotta bring back the car and insist they remove this panel to check for leaks at the fuel filter housing, maybe it's such a slight leak that it never gets to the point of dripping on the ground but just sits there emitting fuel vapors. Sad I have to do all this research myself and that the dealer cannot handle it especially whereas the car is still under full factory warranty and has less than 20K miles.

SW20S

A friend of mine is going through this exact issue with her Range Rover. Dealer cant figure it out either.

I might take it to an independent shop that specializes in Mercedes and pay them a diagnostic and see if they can figure it out, and then take that diagnosis back to the dealer...

Unfortunately Lexus was the same way about diagnosing this stuff. I always had to figure it out myself.

MBNUT1

I'm assuming that they have had it overnight and replicated your opening the door in the morning to produce the smell?

Where is the fuel pump in this car? Is it under the rear seat like the W211?

2012 merc amg

The pump and possibly the filter is on top of the tank under the rear seat as far as I know. Perhaps some of the reason they don't want to go into this area to take it apart is my car has rear center console and Chauffer package so not sure if this makes accessing that area removing the rear seat much more difficult. I'd suspect just one side of the seat (I believe on the passenger side rear) needs to be removed so maybe it's not that big a deal. From the video posted above perhaps it is the plastic housing that has a crack or something as I guess that was happening on a lot of the older E class cars. Don't hear about it much on the S class cars. I really wish they just allowed me to go into the garage and tell them what to do, it would be much more efficient then them getting the car and me leaving in a loaner and then just parking the car in the lot around the back of the building like they normally do. Thanks 39039 above for posting that video, that was very interesting. The more I'm thinking about it that does make sense it could be that housing which is the topside of the fuel pump where the leak is, that seems like exactly where the smell is coming from on the passenger rear side of the car. The only reason I don't get any odor inside the car is due to the sealed plate on top of the housing so therefore all the vapors end up underneath the car.

2012 merc amg

Thanks for posting, good video. From what I understand now the W222 is similar, perhaps it is this plastic housing which is cracked and leaking small amounts when the fuel sloshes around in the tank. Strange though you'd sure think that the EVAP Self test would be picking up the leak and tripping a check engine light. Maybe somebody in the know could comment on this. Dealer says, no check engine light no problem and they cant notice the smell, they will not acknowledge it. It's strong enough where my eyes are watering a little bit when I open the door of the car, seems like thats when the vapors are emitted, there again it goes back to my theory that opening the door initiates the self test and that blows the vapors into the air under the vehicle. I'd be really nervous if I had to store this car long term in a closed up garage, who knows what would happen.