David –

I think you need add more information – the gauge and design of the loco would be a good start, so people can assess its needs more specifically.

Generally though:

All feeds to the boiler – hand-pump, injector and axle-pump – have a check-valve ("clack", or non-return valve) at the point of entry into the boiler. In miniature sizes these are normally small ball-valves that screw into the bush in the boiler, with a copper of fibre washer to make it steam-tight, and the pipe from the feed device is connected with a union cone and nut.

Now. re-reading your post suggests to me that your loco's boiler lacks a "spare" inlet bush for the injector clack. I will say that fitting a bush is not impossible, but my saying so probably now has all the club boiler-admirers reading this, muttering into their tea-mugs.

So, you could siamese the hand-pump and axle-pump into one clack valve to free the other for the injector. I dare say that too would cause some tea-leaf reading, but I have seen it done, you are not usually using both pumps at once, and it's better that the injector has its own pipework including delivery.

Additionally to the clack-valves on the boiler, a pump also has a non-return valve on its outlet, and another in its inlet. Which leads us to…

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… Regarding your loco's axle-pump, if we can assume it is as designed for the loco, then it probably just needs servicing.

My first guess: Blocked inlet pipe to the pump (choked inlet strainer, dirt or a solder blob in the pipe itself).

Second: The inlet valve is not seating properly, so some of the water is simply being squirted back the way it came. Possible causes: dirt, scale or corrosion of the ball or seating; worn seating, perhaps also the ball is damaged or worn.

Thirdly… Does it dribble a lot of water onto the track or try to wash the motion and frames? If so, the delivery side union could be leaking, or too much water is leaking past the ram and out of the back of the pump – a slight seep is not unusual and does lubricate the ram. Causes? First possibility is whatever packing is on the ram (soft packing or O-ring(s) ) has worn down, but should be fairly easy to replace. Second possibility is the ram and/or barrel is/are worn; but only on a loco that has covered many miles. Repairing those involves careful machining.

If the pump is wrongly sized for the loco then the only way would be a complete replacement; but I would think that a highly unlikely problem if the engine was built to a recognised design.

There is another possibility I will raise with due respect and delicacy – driving style! It isn't very likely but if you work the loco hard but with lengthy "station" stands, and it has a very free-steaming boiler, you might be making it use more water than the axle-pump alone can compensate for.

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No I don't think there are such maintenance companies but if there were, their costs for the work I've outlined might make you mutter into your tea-mug. Is there not a model-engineering society nearby you could join, albeit with very restricted contact at the moment?