Chrome locking gas cap

[TomsMB]

My gas cap no longer locks. The key turns the tumbler as required but whatever is supposed to lock the innards to the outside does not work. 
Has anyone disassembled the mechanism and if so, what is the trick?

[lreppond]

Access to the inside tumbler and wafers of a Ymos locking cap will depend on the type you have. If it’s the single sided key model, it’s straightforward.  If it’s the later two sided key type, it may or may not be accessible.

Check the tech manual for an explanation of locks with access holes. If you have the two sided key cap, you may be out of luck if it lacks the small holes which release a clip holding things in place. For some reason some of the two sided caps have them but most do not.

[TomsMB]

Thanks for the response Ireppond. 

After I posted my question, I kept digging through the old postings and found the pages on the locking gas caps.  By following the instructions I was able to finish disassembly, clean it all up, regress the sliding part and reassemble. 

The exciting part is that it actually works for the first time in about 8 years.  I love it.  Small victories make Tom a happy man.

[yves]

Hi Tom , i have quite the same problem with my gas cap, i can't push completely the key inside the tumbler. I have never locked the cap with the key since ..... i have bought the car !
Have you dismantled the mecanism inside the  tumbler ? or cleaning and lubricate?
I wonder if the key i have ( one of the 3 : ignition, glove box and the 3d one for the gas cap ?) is the good one .

[BobH]

Hi Tom , i have quite the same problem with my gas cap, i can't push completely the key inside the tumbler. I have never locked the cap with the key since ..... i have bought the car !
Have you dismantled the mecanism inside the  tumbler ? or cleaning and lubricate?
I wonder if the key i have ( one of the 3 : ignition, glove box and the 3d one for the gas cap ?) is the good one .

Hello Yves, if you have several keys, then the door key should fit the locking cap, unless the cap has been replaced in the past.  I believe the lock number is stamped on the cap and should match the key, unless, as i say it's been replaced at some time

Have you tried, (gently) trying the door key in the cap, or seeing if the lock number matches the door key?

I have 4 keys with my car, as clearly the cap has been replaced at some time, but it still has a Ymos key

[yves]

Bob I have not any number or reference on the cap , only  « ohne luftengang »
But as you can see on the photo the inside of the cap has a screw which is not what I have seen on the other caps , may be a modified cap inside by the PO ? New tumbler ?
I’ll try to see all the parts one by one on the bench.
I don’t know if the tumbler itself can be opened and modified to match my key?

[BobH]

Hello Yves, if the cap doesn't have a number stamped on it, then it looks like it has been replaced

From what i've read you can get the tumblers changed to match your key, it should be your door key that opens the cap

This shows you how to take the cap apart

https://www.sl113.org/wiki/Fuel/LockingGasCap

Good luck

[lreppond]

Yves

I would guess that the tumbler has been modified in some way.  I have never seen any of these gas caps with a central screw. I’m guessing the tumbler was removed and whoever did the work could not get the unit to hold together and drilled a screw hole to overcome the problem.  Have you attempted to remove the screw and investigate further? 

The order of the key cuts as well as the type of key was normally in the very center (if present at all) and may be partially obscured by the screw head. Hard to ascertain from the photo.  These Ymos keys had codes of TA, TB, TN, TW followed by a three number code that corresponds to the wafers in the tumbler.  If this is the car’s original cap, it would use a one sided key and the slot opening on the front indicates that. 

I’d investigate further to see how it’s been modified and if it’s possible to reverse.  I have a box of wafers for several different key ways. I suspect the wafers have been removed and simply not replaced by a PO.  Please let us know your findings. 

[yves]

After dismantling the cap, i have inserted my one side glove box key...! and see that it can be inserted completely with some "effort" .Doing that  , some wafers were flush with the cylinder which mean that it can turn freely and the dent of the key is OK for those , but some other wafers were still non flush.
I took them out of the cylinder prying from the opposite side of their spring inside the cylinder , carefully to keep the spring in the cylinder. I needed to do that for 2 wafers . I grinded the wafers as necessary  so the key inserted in the wafer make it flush with the cylinder surface. ( a few trys were made ! )
After that, the key inserted in the cylinder in it final location cab turn and activate the sliding part with its spring inside the chrome part of the cap
 

[yves]

Some more photos:
Now i have to make ( if i can...!) the metal "plate" showed on the photo from the technical file . That plate avoid the part A blocked with the part B when the key is in the "locked" position.
Photos will be here ..... if I succeed 

[Jordan]

You can actually remove the wafer and the spring and it will not effect the operation of the lock.  Grinding them also works but you can also just remove them.  I did that with one of the door locks as one of the wafers had actually broken, preventing the key from being fully inserted into the lock.  Removed the wafer and the spring and the lock works perfectly now.

[BobH]

Hello Yves, did you find out why someone had added the screw to the hexagon top?

[yves]

Yes I think it is to keep the part A tighted with the B because i have not  any circlip or something else to maintain the 2 parts together
I have not the part numbered 2 on the photo from the technical file which goes in the groove 3

[yves]

Here is the link after refurbishment of the gas cap

https://youtube.com/shorts/zgx4Lq3tzVE?feature=share

[BobH]

That's good news for you and Tom, very satisfying for you both

[yves]

I miss the clip tab which tight the 2 parts A and B together so i threaded the tumbler where was the screw fitted by the PO; and fixed it with a LOCTITE screw so the key can turn the tumbler quite freely.

[H. Keith Henry]

My gas cap key "number" starts with a K, and I don't see a number on the outer (chrome) part of my Mercedes-logoed gas cap itself. Does that mean that my gas cap is a replacement cap?

[lreppond]

Are you sure it’s a “K” and not an “H”?  When the two sided keyed were introduced they were manufactured by Huf (no longer Ymos) and typically begin with an “H”.   

[H. Keith Henry]

My gas cap key definitely starts with a K and is a Ymos key. See pix.

[lreppond]

Yep, no question that’s a “K”.  Whenever you make a declarative statement about a w113, you’re probably making a mistake!   

What threw me off is your car is a 1970.  I thought by that year all cars had the two sided master key.  I’m reasonably certain most of those used the Huf key.  It would be interesting to see if your data card lists the gas cap separately.  Or perhaps it was a replacement part by a PO?

[BobH]

My gas cap key "number" starts with a K, and I don't see a number on the outer (chrome) part of my Mercedes-logoed gas cap itself. Does that mean that my gas cap is a replacement cap?

Hello, do you have separate keys for ignition, doors, and boot/trunk?

After chassis number 010356 cars had a single double sided key fits all, so if you have separate keys perhaps your car was manufactured earlier than 1970, ie 1969, or all locks have been changed for earlier types (not sure if that was possible?)

If you only have a separate key for the cap, then it looks like the original cap was changed for an earlier single sided key type

Just a guess!

[rwmastel]

... so if you have separate keys perhaps your car was manufactured earlier than 1970, ie 1969, ...

In his sig it says "Manufacturing date May 1970".  I would agree with your guess that some PO along the line lost their gas cap and replaced it with an earlier style.  If his doors, ignition are the correct double-sided key, that will confirm.

[H. Keith Henry]

Here's my ignition key, a double-sided key for doors, trunk and glove box. Don't know how to look for it on my data card.

[lreppond]

Go to this link and scroll down to data card #4.  The key code is indicated @ #24.  Usually #25 is left blank. 

https://www.sl113.org/wiki/DataCard/DataCards

[H. Keith Henry]

The key code on my data card says Haupschlussel H: xxxxx. What does that tell us? BTW, my chassis number is 016925.