I cant find a diagram.

I know there is an O ring
There is a gasket at the bottom, hold the cap as it goes into the hole.

Is there a gasket at the top?

So, are there two or three?
Rich

yes.
mhmmmm, i have one in my parts stash. round, corky if i recall correct. brand new, never used ...

it's yours if i can find it ...
Andy

Its ok. I have the material...just not sure If there was supposed to be one there...

Rich

there is a cork square/rectangle one that goes under the whole filler assembly - between the case and the filler.

and then there is a fat o ring in the cap IIRC