ATR-42 Engines wont start cold and dark

Hello guys , so what is finally the procedure to start correctly with the sim ? I try to follow procedures found on the net in tutos and i almost always have a problem with one of the engines not going above 17 %… and i can(t switch off EXT power …Sorry for my english.
How do you do in the end ? what shoud be off and on ?
thanks in advance