Gas filling problems

My 2001 SLK320 shuts off the gas station nozzles just as though the tank were full. This causes me to only be able to get about 0.1 to 0.2 gal of gas in at a time. That makes filling up the gas tank a very time-consuming and frustrating job. This happens no matter how empty or nearly full the tank is. It happens at all gas stations, and is especially bad at some older stations that pump at a higher rate.

I took a look inside the filler neck of the car. There is a black plastic “sleeve-like” thing just inside that is sort of funnel shaped and looks like it is snapped into place. I think it would guide the gas station nozzle to the middle of the filler neck. It has some small slots around it. around it, there are two fork-shaped black plastic segments of it that should snap it into place, I think. There are two larger segments - going around a little over 90 degrees of the periphery that comprise the funnel/guide part. There is something at the top which looks like it could be a sensor of some kind. I can see that one of the larger segments which is the one toward the top has a piece broken off of it about 1/4 inch by 1/2 inch. The 1/4 inch beveled part is broken off for about half inch around the periphery right below what I think might be a sensor. Do you know if it is actually a sensor?

How do you go about replacing this thing?

Of course, I also wonder if the piece that is broken off could be down in the tank causing problems there.

Some other makes of cars have had problems with an ORVR system (Onboard Refueling Vapor Recovery).

Others have said it might be a fuel limit vent valve.

Are these the same thing?

Where are they located?

How do I get this solved?

Thanks, cwsaylor

Somewhere on the filler neck there is a check valve with a hose hooked to it that goes to front of car and goes into charcoal canister.
This keeps gas fumes from getting into the air and if the check valve is stuck or hose is blocked or pinched it will do what you are talking about.
When you filled up in the past did you keep putting gas in after nozzle clicked off, this lets raw gas go down hose and saturates charcoal canister-bad,do not do this.
When it clicks do not put any more gas in it.
Maybe the piece inside filler cap moved and is blocking vent hole, that is what I would checked first.
Then check valve and then whole vent hose.

Thanks. I’ll try to do that.

You’re describing the type of fueling hose where there’s a hose within a hose.

How this type works is, there’s a center plastic hose attached to filler neck where pump nozzle is inserted. On the outside of this center hose is another hose that attaches to the filler neck but vents through the slots on the filler neck.

When gas is introduced into the tank, it fills the tank through center hose. As the tank is filled it vents through the outer hose. If the center hose breaks off the filler neck, the gas is now being introduced into the tank thru the vent hose. And if the gas tank can’t vent as it’s being filled the gas nozzle will keep kicking off.


Do you have any clues as to how I can take this filler neck apart and replace the black plastic “funnel-like” piece?
Is it part of the connection integrity between the inner hose and the outer hose?

I wonder if the two little “fork-like” fingers at the sides of the black plastic funnel/bevelled guide could be how the inner and outer are kept separate. I think the ‘fingers’ of these forks are not tight where they are supposed to be snapped in. I think the tiny ends are snapped off and it is not holding very well.

The filler neck is just below the little rear side window at the top front of the rear right quarter panel/fender. Inside there is a bunch of mechanisms that operate the retractable convertible top. Looks like things are packed in there like sardines in a can!! There is a 3 inch square inspection panel in the trunk side liner and I can see in to where the filler neck starts. I can see the gas filler door lock mechanism because that is the purpose of the inspection panel - to provide access to the lock in case it fails to work electrically.

I really appreciate your help. The Mercedes dealership say they haven’t a clue as to what the problem is, and they want me to bring it in. It sounds like I would be paying for their learning curve!

Perhaps the solution is removing the filler neck from the car, removing all the unnecessary parts it contains, and reinstalling the now free-flowing filler neck. Cars were fueled like this for 70 years without any problems…

That is very tempting; but, with my luck, the CA EPA and the Fed’s would be arguing over who wants to be first to lock me up for violating their government edicts.

Mercedes dealer said there are only three replacable parts pertaining to the gas tank.
1.)gas cap, 2.) the black plastic funnel-like guide inside the neck, 3.) the fuel pump.
Otherwise the whole tank and filler neck system has to be replaced for about $1500.00 (I remember when that was a lot of money!)
I bought the funnel-like part which is now made of white plastic. I am almsot certain it will not fit my car!!
I took some of the clues here on this discussion site, and I got a three foot length of hose - it is gas line hose and kind of stiff. I stuck it into the tank. It met with some resistance about 10 inches in and about 18 inches in. I rotated the hose while sticing it in past the slight resistance place at 18 inches so that I could push on “Whatever” all the way around. It is into gasoline at or just beyond that point. I then went to the gas station and has no problem putting gas in for the first time in a year!!! Thanks for the clues. I hope I continue to have no more problems. I used 5/16 inch hose(inside diameter). The outside diameter is about a half inch.

This post should be permanently displayed anytime someone starts a 'I can’t get gas into my car" thread.

I have been beating this drum for years and offering the solution you discovered. Forget the “carbon canister” nonsense and instead work to dislodge the stuck check-valve as charlessaylor did successfully…

There is one truth in the “overfilling” warnings. When you overfill the tank, the check-ball floats up and plugs the filler opening, preventing further over-filling. BUT…In some cases, the cork (yes! Cork!) ball swells up, being submerged in gasoline, and sticks in the closed position, preventing the next attempt at fueling. Sorry, non serviceable parts, you must buy the entire tank assembly, $1500. Benz over. That’s outright thievery.

I will humbly take my bow and offer you “High Five”. Thanks

"Mercedes dealer said "

I suggest you find a local INDEPENDENT mechanic familiar with Mercedes. You will save a lot of money and may well get better service.

Good sugggestion.