Use synthetic oil. Make sure battery is strong and starter spinning well. Then wait 40 seconds after the glow light goes out before starting. That extra 40 seconds makes all the difference in the world in my 77 300d. It won't start without that 40 second wait. Don't be afraid to keep the starter engaged if it initially only fires on a couple of cylinders.
Also, adjust the valves. If all else fails, do a compression check.
I have heard repeatedly that it is not wise to use ether in a diesel with prechambers. I would not use ether myself. You could introduce some hot air into the combustion chambers with a heat gun or a propane torch shooting into the air intake.
1977 300d 70k--sold 08
1985 300TD 185k+
1984 307d 126k--sold 8/03
1985 409d 65k--sold 06
1984 300SD 315k--daughter's car
1979 300SD 122k--sold 2/11
1999 Fuso FG Expedition Camper
1993 GMC Sierra 6.5 TD 4x4
1982 Bluebird Wanderlodge CAT 3208--Sold 2/13