That sounds like a fairly typical description of old fuel containing ethanol, Aldo: the ethanol has become combined with water by absorption. The yellow smelly stuff seems to be prone to blocking things up. Gum formation in old fuel is a separate problem, mainly relating to fuels with a high proportion of cat-cracked constituents. Olefinic hydrocarbons of that type are not very stable in the presence of oxygen, and the oxidised products include gum.
This oil company bulletin may be helpful (note that the reference to "oxygenates" relates to ethanol, methanol, and certain octane improvers used in the US).
http://www.chevron.com/products/prodserv/fuels/technical_safety_bulletins/ltg_background.aspx
