I use to have this exact same issue. Here is what I did to fix it:
Upgrade to Blender 2.77 or higher
(earlier versions did not work)
Set the unit scale on your Blender
project to be 1 CM (this is the scale
UE4 uses)
Apply any scaling you have prior to
exporting
Use the FBX 7.4 Binary exporter with
Z Up and Y Forward, Smoothing: Face,
and uncheck “Add Leaf Bones” if you
are exporting skeletal meshes.
After following these steps I can now export my characters into UE4 with no issues (my characters always use to be face down and so small it threw an import error in UE4).
So I just finished and rigged a model in Blender, gave it a skeleton and exported it as an .fbx, but when I import it into Unreal, it’s small and in the wrong rotation, so I export it again, but change it’s scale and rotation to try and fit with Unreal, but it doesn’t work!
No matter what I set the rotation to, it is always facing face down, and no matter what I set the scale to, it is always tiny, in fact the higher I set the scale, the smaller it gets (and if I set it less than 1, it just stays the same as if I made its size 1)