Ron – I think you need to sit down and think about things.
Axle pump – water goes in the bottom, out of the top, one pipe goes to a clack on the boiler, the OTHER one is the one that goes to a valve that allows water to go back into the tender. If THAT "bypass" valve is closed, pumped water goes into the boiler; if it is fully open, water goes back to the tender.
Figure out how to do the axle pump. Remember that:
– Water from the tender to the bottom pump connection is at atmospheric pressure;
– Water from the top is at boiler pressure (plus a bit) so the piping to the bypass valve is at pressure – no plastic piping here!
– Usually, the output from the bypass valve goes down a pipe that ends up somewhere where you can see it, for instance, in the tender under the water filling hatch. ("visual feedback"
Hand pump – pressure piping, again.
Injector – steam in one end, water in the bottom, the other end piped to a clack (or two) for water going into the boiler. Generally, one has a water valve to stop water flowing when the injector is not on.
Don't worry overly about the injector right now, get the axle and hand pumps going.
John.