That 20 seconds on the electric pump was what we were doing. It was like that for a couple of years, didn't think much of it but noticed it fires right up with the new injectors.
I haven't replaced a timung gear driven pump. Our 9080 is not what is now termed common rail, the gear pump only goes to like 70psi from memory and the unit injectors make the high pressure from the camshaft. I think all 9080s would be like this.
You can get an air pressure test done on the fuel rail and injectors and look for bubbles, with the tappet cover off I could see fuel wash from the faulty injectors. The rocker gear has to be removed to get the injectors out. There are a couple of special tools involved to turn the engine and a timing pin.