Some fuel line fittings need a special tool to remove. Check a Haynes or Chiltons manual. If you do need one, they're cheap and you can find them at any auto parts store. This is what they look like.
http://www.drivewerks.com/catalog/ShopCart/TOOL/POR_TOOL_CAT405_pg4.htm
http://www.drivewerks.com/catalog/ShopCart/TOOL/POR_TOOL_CAT405_pg4.htm
