Working like a charm (no jinx!). Took the new pump out of the pit and raised the float and it did kick on, so knew it was not the float. The float was just not sitting right in the pit and couldn't rise as it needed to. Readjusted everything (well, my brother did), and everything worked fine ... except the pump wouldn't go off. Alas, the float could not come down now! So readjusted again. Also got a new check valve (exact same one as we had before). Now everything is running smoothly. The funny thing is when the pump would run before there was always a pretty loud bang at the end (the check valve shutting?) but I thought nothing of it (had been this way for 10 years since I've owned the house). Now, you can hear it but very quietly. Is it the check valve that makes that noise at the end? Weird.