It does feel like a mechanical problem, but the resistance is momentary and minimal. It spins very freely.
I've just checked for repeatability as follows...
Turn pump with screwdriver, turn on system - it works.
Turn off system and wait a minute.
Turn system on, pump doesn't run.
Turn off, twiddle the screwdriver in the pump.
Turn on, pump now runs and everything ok.
So, in effect it seems I now have to twiddle it with a screwdriver every time to make it work.
This is worse than it was a few days ago, where sometimes it did start by itself.
Seems like it is probably stopping at the same angle each time, probably due to a bit of resistance there, and that resistance is preventing it from starting.
The pump is 7 years old, and I wonder if it is really worth stripping down, or better to just replace?
Amel 54 #154