thanks for the reply.
my block heater is a defa coolant pre-heater element and is working, the hot retern hose from the engine block is warm after about an hour in -20. and with my old car even with out pre heating it would fire up in this weather in 2-4 attempts. i was thinking of adding in a defa 715 thermostat controled unit i took of an old car of mine.
http://www.defa.com/doc/25608.967112894.productxdescriptionengineheater.pdf
together with my existing one so that i have duble the heat. but it sould have still started when pluged in for 2 hours. the engine was warm! you don't think it can be air in fuel system? what else can cause this?
p.s. i noticed that my starter was a bit weak. not by much and it turned over nice on the first attempts so....