Grrrrrrrrrr! I hate pumps that won't restart!

[Reef Pilot]

I have a couple mag pumps, and one of them, too, wouldn't start up sometimes after powering off. I totally took apart the impeller unit, shaft, etc, cleaned every bit of Ca deposit, and it still wouldn't start consistently.

I had another mag pump that was similar, and was able to switch impeller shafts, and that solved it. In fact, both now start up every time.

It seems that the shafts and/or bores may get a wear pattern over time that causes this. By switching impeller unit parts, the wear pattern is changed around, eliminating some slack. At least that is my theory.