A bit late, but the problem turned out to be a loose washer under the engine! The guy fixed it within 10 minutes and the engine has worked like a charm since!
As of the cranking too long to start problem, you were right, the cause was a leak at the diesel pump. The guy replaced the gaskets at the diesel pump and it starts instantly ever since. As of now everything is working fine.
Tuesday, February 25th, 2020 AT 12:08 PM