I was at Lake Tahoe a few years ago, high altitude and about 30*F, '80 300SD which usually started easily. It wouldn't start with my foot on acelerator about 1/2 way which is what I usually do.

For some unknown reason, I left my foot off accelerator and it started. From then on I didn't step on accelerator and it started easily.

I have no explanation why it wouldn't start with accelerator depressed in the cold high altitude.

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