Replaced the start.elf with one from the lastest raspian-stretch. Now its all working!
I cannot found the start.elf file. It is supposed to be inside the /boot but apparently it's empty. Where do you find it? can you put a link of the one you used?
this worked for me too, before using the start.elf from the latest raspian-stretch, the pi would only blink red 4 times slow, 4 times fast