My 2002 Ford Ex with the 7.3 Turbo Diesel had no problem last week with the low about 24 degrees. I don't plug it in anymore since I installed two yellow top Optimas. Even up north in January it will fire. Does need to crank allitle.
Was it slow to turn over due to the weakend battery, or was it a fuel problem? Also, check your fuel filter and water separator.
Get it ready because you know whats coming!