You can do this key on, engine off. Turn key on to the run position. You'll hear a faint whine which drops off in pitch and then stops. Your anti-lock/Brake dash lights should go out within a few seconds. When it stops, depress the brake pedal a number of times and count how many presses you get before the pump comes on again.
If the pump runs with fewer than 3 presses (i.e. 1 or 2), then you most likely have a worn ABS accumulator. Especially, if the anti-lock/brake lights come on briefly and then go out again.
Let us know if what happens and if you need part #s or suppliers for replacements.
Hope this helps.