As far as I could find out from the documentation and various discussions on the net, the ability to add default values to fields in a scrapy item has been removed.
figured out what the problem was. the pipeline is working (code follows for other people's reference). my problem was, that I am appending values to a field. and I wanted the default method work on one of these listvalues... chose a different way and it works. I am now implementing it with a custom setDefault processor method.
class DefaultItemPipeline(object):
def process_item(self, item, spider):
item.setdefault('amz_VendorsShippingDurationFrom', 'default')
item.setdefault('amz_VendorsShippingDurationTo', 'default')
# ...
return item