Won, t start

If you have to prime it to start it then,as you probably know,there's air getting in.
anywhere from the tank up to the filter and to the high pressure pump.
or the fuel rail pressure is low.

Injectors shouldn't be a worry at this point.
But it would be super helpful to "see" rail pressure in graph form,just to rule out in tank supply pump faults.
So undo and refit all supply pipe connectors and filter seals
when squeezing the primer bulb it really ought to go hard after 2 or 3 squeezes,if not then there's an air leak .

Leakback check needs to be done on the injectors. A diagnostic check may pick up the faulty ones. It sounds like an m9r engine and injectors are notoriously problematic in these engines.