As the headline says.  This is a 1982 air-cooled van.  Daytime, when it's a little warmer, it starts right away.  But somehow at night or early morning, when it's a little colder, it won't.  
I know, there are two temp. sensors and usually the temp. II sensor is the one I would change.  I just haven't experienced this kind of behavior.  
Maybe none of you would know and send me a message about it, and I will go out and buy a Temp. II sensor and see if it works.  But what if the Temp. I (one) sensor is the one that is not working as it should?  I never heard of that to be changed.  
My respects to the List.
Zoltan