Hello Ryan,
Going back to first principles, the locomotive was a good runner when you got her which indicates there isn't too much wrong. Firstly, the axle pump, start by filling the tender and checking there is a reasonable flow from the appropiate connection. Next disconnect the union on the pump inlet and see if that same flow rate occurs at the pump, should all that be in order, then the inlet ball is stuck on it's seat. There are several ways of dealing with that, you could undo the seat from the pump body and release the ball that way, but a couple of ways that may work are to give the bottom of the pump inlet a sharp tap using a small hammer and a copper drift, or some times pouring a kettle of boiling water over the pump will release the balls! Once you think the inlet is free open the by-pass and with a water supply connected to the pump turn the engine over, the pump will force a stuck outlet ball off it's seat and water will be directed out of the by-pass connection. Should you have to take out the inlet ball seat it may be worth popping it in the lathe and drilling right through, tapping the underside say 4BA and fitting a plug, so at any time later the should same situation occur it's easier to take the plug out and push the ball off its seat with a match stick.
The injector, if it was working before it should only need sitting in a drop of pickle, kettle descaler is my favoured method. Again check the water flow from the tender and remember it is imperitive there are no air leaks in the water supply line, check the filter in the tender sometimes the crud builds up on the filter and they will work like a tube so whilst there maybe a couple of inches of water in the tender there may only be a fraction over the top of the filter and air is then drawn into the injector supply pipe. Again check the the flow through the delivery pipe; I'll sometimes make a connection to the mains water supply via a modified garden hose connection when checking water supplies on our miniature steam locomotives, always useful.
Anyhow, best of luck; I consider Maisie one of the finest designs the old chap gave us, i've seen them from the dog rough to medal winners, but the all go well. take a little look at this Youtube clip, wonderful: –
http://www.youtube.com/user/ianp6155?blend=6&ob=5
Regards,
Bob Youldon