When I first bought my 79SD back in November it wouldn't start in the low 20's. I suspect this is probably why the PO put it up for sale. He had recently moved from the south to Colorado and we'd had a couple of cold spells prior to his listing it on Ebay.
Today it was 12 degrees and it fired right up. I've changed the glow plugs, reamed the holes and switched from dino to Shell Rotella synthetic. The two things that seem to have made the most difference are the synthetic oil and reaming the glow plug holes. I initially just put in new glow plugs since I did not have a reamer. They made little difference. I bought a reamer and now it is a much better cold starter. It's still not quite as a good a cold starter as my two others. I wouldn't count on it at 35 below.
Of course, I've also added a lower radiator hose heater so that this will be a non-issue in many cold circumstances. I did not have the heater on today.

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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

Thanks for the info. Reaming is one thing that I have not done yet. I wasn't really sure if it was worth it or not. I am good to about 20 degrees. Things get a bit -iffy when it drops into the lower teens though.

Have you adjusted the valves or checked compression? Usually cold starting issues are as much about low compression as they are GPs. Something to consider if it is still marginal would be the valve adjustment.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

My valves are adjusted regularly, use syn oil and my compression was all pretty near 350 (I don't have the exact numbers, some were a bit higher, some a bit lower, but all were close to each other). I guess I thought 350 was pretty good, but I'm not really sure now that I think about it. Plugs all test good and glow nice and bright.

With 250K you might have a timing issue too...have you ever had the injector timing checked? 350 PSI should is pretty good compression. Also, one trick is to double-glow before starting (or just keep the key in the glow position for an extra 20-30 seconds after the light goes out before cranking). That can make a difference too. It is better to let the glow plugs get extra hot than to try and heat the combustion chamber by cranking.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

Valves were adjusted shortly before I bought it. Compression is at 300psi dead cold at 5280' altitude so I consider it good. I checked the compression immediately upon experiencing a cold no-start to make sure I wasn't wasting time on other improvements.

__________________
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

Have you tried to double-glow it?

Does it sound like it is cranking fast enough? Sometimes the starters get weak and just can't turn the engine over fast enough when it is cold out.

__________________
Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz

I checked my camshaft timing, but not my injector timing. I see that there is some sort of drip method involving unhooking the metal lines. Is this a difficult or even accurate test? I have always assumed that my starter is just too worn to start when real cold. When it is in the low teens, a few cylinders will start to kick in, but I have to keep it cranking for quite a while until all five kick in and take over. Not sure if this means anything or not.

If my current efforts had not improved the starting, the next thing on my list was a Mean Green Starter. The starter seems to be turning the engine at adequate speed.

__________________
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