I have had trouble starting my 1979 300D every winter. I only have trouble now when it gets in single digits as today it was 9F. My car just simply doesn't have enough boost to start it. I have been using diesel kleen, but don't understand how a lot of people get their diesels started in -20 weather when I can't get it started in just 9F. Let me know what I should do. Also how do you keep the door locks from freezing up on the outside of the car???

Put the starter off the turbo engine in your car--it is a faster spinning starter I believe.
If you have the old series style glow plugs--convert them to parallel plugs with the kit or just buy the parallel adapter plugs and wire them up on your own. No need to change the relay.
Use synthetic oil.
Glow 3 times before trying to start.
Put in a block heater or just plug it in if you have one.

Did the first 3 to my 77 300d and it made a world of difference. Used to have trouble starting below about 20 degrees. Now it starts on first crank down to about 5 degrees--hasn't been any colder to test it at lower temp. Biggest difference was the parallel plugs.

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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

Well mine will start down to about 11 or so, but when it's 9 or below I can't get it to start. I live in an apt, so kinda hard for plugging in a heater or battery charger. Not sure how to do the starter stuff. I always do the 3 glows though.