Thanks, Eddie.

I swapped out the extension cords that the pump was plugged into with some others and plugged them in to the GFCI outlet and it tripped. I misspoke in my previous post; rather than 15 minutes, it's more like 2. I hadn't paid close enough attention to the times. I then ran those extension cords into the house and plugged them in another CFGI outlet (bathroom). Same as before; ran about 2 minutes before tripping.

Based on this, I don't think it's the extension cords or the outlet failing.

This is the third summer with the pump. The pump had stopped working before I cut the CFGI box off the cord and replaced it with a standard plug. I had been assuming that I botched installing the new plug but I suppose it could be the pump itself. The connections in the new plug seem pretty tight and I was pretty careful not to have a loose wires sticking out to create a short circuit.

Donovan