Just temporarily bypass the fuel cut off switch, do you notice if there is any particualr time it does it such as after bumps in the road for example ?
I am not sure of the location on these, but look in each footwell area on the side kick panel and you should see the hole for the reset switch where you can push the button down.
I don't think it is this though as you don't say it has popped and they cannot reset themselves.
It may be a dicky/lazy pump, especially as you say other ones are faster.
Have you changed the fuel filter recently, if not I would do that anyway.
tabetha