[Oldsguy]

GM uses a mechanical cam that runs off the wiper motor shaft, this cam drives the pump and it is activated by a switch located on the wiper motor. Look at the wiper motor (mounted on the firewall, driver side) it should have a black plastic housing which covers it and there should be a wiring connector facing the front of the car, this connector should have two wiring harnesses attached, one is for the motor, the other is for the pump, I can't remember which one is which. Inspect both for any signs of corrosion, clean them up with some alcohol and an old toothbrush or something if you find any corrosion. This might help. Also, most auto parts stores sell a repair kit for the wiper motor for GM as almost all of them were the same, again, I am not sure how much or exactly what is in the kit. I have done it before but it was a long time ago. Good luck and welcome to our site!