The fuel filler flap certainly should lock with the central locking system on your car.

My Owner's Manual also describes an emergency release button/handle for this flap located in the trunk, behind the right side trim. Turn this clockwise, and a locked flap will be released.

I haven't tried it out myself, but it must be there surely.....

 

Most Benz have this feature but simply bending the trim back to get at it is not enough, the trim has to be removed.

 

yes that happened to me at a gas station near canyonlands national park in utah. I had a quarter of a tank left, and it would not open. Early in day in Flagstaff where I had last refueled, it briefly would not close, but now in utah it would not open and there was nothing I could do.
I drove into moab to get some assistance the next day. I called my service technician and he was unable to offer a solution. the gal at roadside assistance told me press harder on the flap, which I did, and I dented the flap.
I followed the instructions in my owner's manual. When I turned the fuel filler flap key clockwise like the book said, it twisted off completely because it was made of some sort of cheap tin like material. I seemingly had no option and no way to refuel, and I was 450 miles away from the nearest mercedes dealership, and 1,100 miles from home.
Then as I was talking with my technician, it magically opened again to my relief. I made a macgyver style fix with an energy bar wrapper that prevented the filler flap from closing again until I got home the next day.
After taking off the wrapper again, I closed the flap, and again it would not open. Then the next day it magically opened again, but would not close.
That is the situation. I got some advice online to change the "fuel filler flap lock actuator" which I understand to be the little bar that moves in and out to lock the flap. I haven't tried that yet.
What a nightmare to be stuck in the desert without gas. It makes me want to stay at home in case something else happens that is beyond my understanding, and that of the roadside emergency assistance rep and my service tech who explained the difficulties they face in understanding the variations between the models (his colleague thought I could unlock the flap from my driver's side door and that the way to unlock it from the trunk was to pull a lever rather than turn a tin key).
I should add that this is the only real problem I had on a half dozen road trips through the US over the last year since I bought my car with 40,000 km on it. I love it, and it has given me much traveling joy. But what the flap!!!???

 

I had the same problem. There IS a manual release in the trunk behind a panel and in my case behind the soft top mechanism, that I could not reach. Fortunately I was in town and could get to a dealer. They replaced the cable connector from the fuel filler door to the locking system under warranty. So far, no addition problems.

 

Gas tank flap won't open

This happened to me ,got to a gas station and the flap won't open. I stood there like somone who had stolen the car and had no clue as to how to open the flap. In my case I had left a light on the previous night so the the battery had run down, i therefore took yhe car for a spin to charge the battery. Since the car couldn't open using the remote keyless entry, I was forced to use the metal key meaning I had circumvented the central locking system. After I got home without buying the gas ,figured I had to lock the car remotely and open again to engage the central locking system and viola the flap opened. Problem solved!

 

Now clean up the moving parts, and add some lubrication..

 

I took my CLK to Mercedes Benz in Colindale, London the they ruined my car. There is an issue with the central locking in that it does not respond from long distance only at short range along with a battery drainage. In trying to determine the cause of the drainage MB Colindale examined all the fuses. After a week or so after the car was delivered with a number of issues like the glove box mechanism broken, I wanted to fill up and guess what? The petrol flap wouldn't open! With very little fuel it caused a great deal of stress since the emergency flap release had been broken by the dealer!. So no access to the petrol cap . Thanks to the excellent forum we have here that a member suggested checking Fuse 15 which controls the petrol flap lock. I checked to see if it was blown and you know what it wasn't even there! I went to my local Halfords and bought a 7.5A fuse placed it in fuse 15 slot and hey presto it started working! The moral of the story is that all dealers that I have come across are incompetent rip off merchants and you will end up with your car in a worse state than it did before taking it to these thieves, cheats and liars. I hope this will help others having issues with fuel flap not opening since in many cases it is just a simple matter of pressing the remote to arm and disarm the central locking but when this fails a simple electrical problem such as a blow fuse or no fuse as in my case can resolve the problem. The other issue I have is in the manual it refers to the fuse allocation chart being in the the side of the dash board. Well it is not there and MB make it very difficult for owners to resolve issues themselves.

 

You'd be surprised how many of my fuses have suddenly gone missing after I had a service done at the mechanic.

I took my CLK to Mercedes Benz in Colindale, London the they ruined my car. There is an issue with the central locking in that it does not respond from long distance only at short range along with a battery drainage. In trying to determine the cause of the drainage MB Colindale examined all the fuses.

 

Hey guys...I've been out the loop for a few months. Was out the country on an emergency. But I'm back in the states.

Today in Miami I was at a gas station, about to pump gas...I press my fuel tank flap and it won't budge. I locked and unlocked the car numerous times and it still won't open. So all I could do is drive back home with a quarter of gas left I the tank. I tried to find the manual release by going through the trunk (pg 407 in the manual) and I still can't find the release. Has this ever happen to anyone? I don't know if it is that my arm is too short, but I physically got into my trunk pulled the panel back and still didn't find anything.

I have an appointment at Mercedes tomorrow 5:45 pm, but they weren't even bright enough to know their own brand. They told me that there is no lock for the fuel tank flap, I told them there is a lock, it locks when the car is locked. Any help woyld be appreciated.

Hi did you manage to get this sorted, it's started to happen on my A-Class, just taken it to the garage and waiting on a price to fix. How much did it cost if you don't mind me asking. I thought it was going to be a easy fix but he was talking about taking my wheel off and wheel arch and I thought this was a bit extreme.

 

Howdy, after browsing through a lot of these reviews, I went out to my 300 glc, 2018, locked and unlocked it several times with the fob and voila!! opened, no problem. Try this first!

 

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You are replying to a 3 year old thread, and this is the CLK forum, but you have a GLC which s a totally different vehicle. Your car's forum is here:

https://www.benzworld.org/forums/x253-c253-glc-class-2016-2021.409/