Are we talking about # 13 in this diagram?
http://www.pelicanparts.com/914/parts/engine/distributor_small.htm
If so, is the diaphragm fixable? From the diagram, it doesn't look like there's a way to get in there, and from first glance at mine, unless you get to the innards via the 'bottom side' of the device, I don't see anything to take apart.
Thanks :-)