In a good engine the compression should go up when tested hot - the pistons, rings, and cylinder liners grow toward each other and the lubricating oil should still be on the cylinder walls. Whether or not you can tell the difference depends on your gauge. Generally you do a cold test and a leakdown test. Hot tests can be dangerous so they're generally reserved for those oddball scenarios.

By the way, how did the car run and what work did you do just before the no-start? Diesels are simple and lots of people here can help.

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daBenz - 1970 220D