Hi Ron,
Sorry to hear that you are still having problems.
Can you borrow an injector that is known to work reliably e.g. that is taken off someone else's loco? Swap that for one of yours and see if it makes any difference. If the other injector works then it's your injectors that are the problem. If the other injector doesn't work either then there is something wrong with your pipework etc.
Your problem suggests two possible causes to me (assuming that the injectors are not at fault). Either the steam supply to the injector is restricted somehow or your clack valves may not have enough lift on the balls.
Are you using commercial valves for the steam valves? Sometimes the passages through these valves are too small, especially on the globe type valves.
Injectors often need more lift on the balls in the clack valves than those used for hand pumps and axle pumps.
What size injectors are you using? If you are using say 24oz then try an 18oz. The smaller injector will need less steam and water so may work if the supplies are not enough for a 24oz. If the 18oz does work then you need to look at the steam and water supllies.
Have you got filters in the tender for the injector supply? If not, you could be getting muck in the water supply which will stop the injectors working after a time.
Be careful not to go overboard with pickling the injectors. The acids will eventually damage the brass cones and affect performance.
John
Edited By John Baguley on 14/02/2017 07:21:05