Thanks for the reply Paul,
All the diesels I had worked on had injector pump distribution tubes to each injector (as you probably know) - that’s why I was unaware of a “rail”.
I copied this from a Yanmar manual.
injector pump pressure on yanmar 2GM20FC
The 2GM injector opening pressure is 170 kg/cm2 …plus /minus 5. Thats between 2347 PSI to 2489 PSI.