ABS Pump or Accumulator

[poko]

I have a 1990 RRC and the abs pump kicks on about every 40 seconds, even when the car is just sitting idling. It only runs for about 3-4 seconds then shuts off, then 30 to 40 seconds later kicks on again. Is this okay? The abs pump appears to be a replacement, the accumulator is the original. What do you think, abs pump or accumulator problem?
Thanks

[kevin-ct]

look for leaks.

[Les Parker]

Do you have the ABS light on the dash?
Is there evidence of any brake fluid loss?

[poko]

No lights, brakes working great, no fluid loss.
Thanks

[kevin-ct]

No lights, brakes working great, no fluid loss.
Thanks

I would guess it the accumulator then

[Terrys]

Both.
If the pump only runs a few seconds, the accumulator is shot. The diaphragm between the brake fluid side and the nitrogen side has rotted out and you can't compress brake fluid, so that's why the pump only runs a little bit at a time. However, since the pressure is bleeding off, to the point where the pressure switch turns on, and there are no leaks, the only source of the pressure loss is the check valve in the pump.