My '80SD didn't want to start at lake Tahoe either at about 30 F. Normally when I start the engine I step on the throttle about half way. For some unknown reason I tried starting it again without pressing on the accelerator and it started easily. After that I didn't step on the accelerator when starting and I had no further problems. I have no explanation why this worked. I was at Tahoe this year and had no trouble starting but it was warmer this time.

It does make sense that a Diesel would start harder at a high elevation. The air is thinner so there is less air in the cylinder to compress therefore the temperature inside the cylinder created by compressing the air will be lower. If an engine is leaking compression, high altitude will exacerbate the situation.

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