what Jerry says makes me think of another possibility: you may have a worn actuator arm on the pump or a worn lobe, either one resulting in not moving the diaphragm far enough to keep up with full load demand
"When we tug a single thing in nature, we find it attached to the rest of the world" ~ John Muir "When we tug a single thing on an old truck, we find it falls off" ~ me Some TF series details & TF heater pics
