Thanks for the thought about rubbed wiring. lifted the hood - no rubbed wiring, but found that the flared fitting on the fuel line, where it goes from metal to flexible, to go to the water trap_filter, was loose. The fitting uses nylon type compression fittings, not brass. Tightened them up, but have not been out to put a load on the engine yet. I think that maybe the filters that needed replacing caused the pump to suck air at that loose connection, then the path for the air was still there after I fitted the new filters. As this fitting is way up above the fuel tank, no sign of a fuel leak was visible.