A 310 diesel is very high on my attractiveness ranking. Congratulations on that. As a former diesel mechanic, the first thing that came to mind was the turbo, since it stops after warm-up. If the injectors were at fault, not only would it not stop, it would get worse under load.
On the other hand, it probably could be worse. According to legend, the Canberra English Electric Canberra - Wikipedia, the free encyclopedia
used a starting system that emitted so much smoke that ground crews that didnít know rushed over with fire equipment! One is currently undergoing restoration at Little Rock Airforce Base, but might have American engines.
After a few fun moments exploring Wikipedia, I came on a photo of the American variant being started. Apparently, no difference. Your 310 has
to be better than this.