Fit a tube to the boiler side of teh clack valve so it takes the water down below water level.
You will need to work out the amount of steam you are likely to use and work back from there as far as pump and injector, but look at other traction engines of similar size to see what they use to make sure you ar ein the right ball park. Without knowing the cylinder size, stroke, rate of work, boiler size then its hard for anyone here to give a definate answer.