I'll answer my own question (regarding using a fuel injector as a primer valve between fuel line and rotor housing  oil injection hole).

I did a bit of testing with air. Injectors will open at about 20  - 30 psi back pressure.
So with low pressure fuel pump (2.5 - 5 psi) the obvious solution is to mount the injector backwards.

However, this is probably a non-issue. The oil injection port (hole) in the rotor housing closes about the same time as the secondary (aux) port, so there really shouldn't be any backpressure to amount to anything (normally aspirated).

Expecting to finish installation and do a test tomorrow. Maybe even a picture...
Although probably not of interest to anybody else on this list. Most are using fuel injection anyway.

Finn

Finn Lassen wrote:

I changed my mind and am installing the primer line in one of the oil injection holes in rotor housing.

It just occurred to me that the compression in the rotor housing could force the fuel injector open and force the fuel out of the fuel lines.

Any idea of at what pressure (on the output side) our fuel injectors open when there is no (or little - 2.5 psi) fuel pressure on the input side or the fuel injector?

Finn