I had this problem in my 2005 roadster and had a row with the Morgan factory about it. The pipe from the filler cap to the tank is made of NBR (nitrile butadine rubber - a fuel resistant rubber) which, however, is inherently very hard and inflexible. It require 10% plasticiser in it to keep it soft. The trouble is that the ethanol now put in many grades petrol leaches out the plasticiser causing the rubber to become brittle and crack. I was genuinely able to crack a walnut with my fuel pipe.
Despite much correspondence the factory denied that this was a 'known problem'.
John
