Selgas
Just a tip here – Pumps can LOOK and FEEL and SOUND like they are running properly but I have known the impellor to be adrift or loose on the motor shaft and not spinning with the motor – this has lead me to identify many times the same problem you are experiencing there – check it out and see if this is what has happened. 
Selgas Services Ltd
Craftsman Gasfitters, Plumbers, Electrical Service Technicians
