pump hums but doesnt start

[junklar]

Hello all,

I have a AO SMITH UST1102 1hp pump. The pump hums but won't start. If I hit it with a hammer, it starts and will continue to run all day until it shuts off by a timer. When it shuts off it won't run again unless I hit it with a hammer.

What can be the problem?
How can I fix this?

 

[jblizzle]

Sounds like the start capacitor(s) could be bad.

I am not very clear on how to test them though ...

Or maybe the centrifugal switch is sticking?

 

[Bama Rambler]

Sounds like the switch contact to me. Take the back cover off and clean the contacts.