Classic ABS

Hi, i have an LSE classic with ABS fitted and i'm trying to get the brakes to work. The pedal is firm but there is very little stopping power unless you pump the brake pedal. The ABS pump didnt seem to be running so i took it apart to clean the filter inside and then re-assembled it. The pump runs when i put 12v across it but it just wont run on the car. I've checked the 3 relays under the passenger seat and they all seem to work ( click when 12v applied and when energised, give continuity across the other 2 pins.
Then this evening, i swapped the two rear-most relays over ( they look identical) and for about 30secs the ABS pump ran?? I opened the bleed screw to try and prime it but then it stopped running and now it wont run. The two relays are both still functioning.
Please can someone point me in the right direction on this as i feel like i'm getting nowhere?
Thanks

Update.....just went out and tried the brakes. Its working again
Does anyone know how long the pump should run for to charge the system?
Thanks

The time to run is dependant on latent system pressure....

In the P38 RAVE manual (the LSE and LaterClassics basically had the same system) there is a graph giving time over pressure information.

Roughly, from a 0 pressure situation, around 40-50 seconds to fully charge the accumulator.....if the accumulator is fairly charged...5-10 seconds mostly.

The pump should only run on every 5-6 pedal pushes, if it runs every 3-4 the accumulator is tired, if it runs every 1-2 pushes, the accumulator is shagged.

Thanks for the help. This sounds promising as I think the pump ran for about 1 minute and presumably the accumulator would have been completely discharged when I removed the pump? Today I will try and see how often it runs.
Will I need to bleed the system? ( I'm a bit worried i might be damaging the pump further running it at the moment?