1965 190D starts and runs fine when on engine heater in mildly cold weather but starts hard after being left unplugged in a parking garage for the day. Any suggestions.
Are you glowing the glowplugs?
You shouldn't have to plug in that block heater till it gets down to maybe 20 degrees.
If you don't know how to glow them,do a search on glowplugs at the top of the page.