Try using a volt meter and check for close to battery voltage at the power lead to the pump (According to Haynes, it's a black with whit stripe wire) when you press the wash button. If you don't have power there or very low power there, check for power at the switch (Same color wire), if you have power there then it's probably an open in the wire between the switch and the pump, if you don't have power then it's likely the switch. Just to be on the safe side, also check the fuse, although it looks like the fuse provides power to both the wipers and the washer, so that's not likely.
If you do have power at the pump, check the ground for the pump.
Good luck
Pat