Can someone help me with my locking fuel cap

[vdubskunk]

Hi I have a early bay (71) and the petrol cap is a lockable one. I have the key and when I turn it a single pin/bar comes out from the side. The thing is I don't get how it is supposed to work. I have taken a few photo's below to show what it looks like. If anyone can tell me how to operate it or if it looks broken.

Many thanks
C

 

[Clarkson46]

The pin that slides in and out locates in one of the 4 notches in the lower part. In this mode you can tighten the cap onto the filler neck. Now turn the key the pin pulls back and the outer cap just spins free preventing the cap being undone. I suspect that whatever held the 2 parts together is missing possibly a circlip and washer, but that is a guess on my part.

 

[Araon]

WHS^^^ but I believe that within the lower part should be a spring clip so that you snap them both into place the upper will spin freely when the pin is pulled back....