Recently just went through this.
old shurflo 2088-403-144 original pump that was standard in everything. switched to the the same thing in the updated model. shurflo revolution series.
the hum is more then likely the microswitch. if you wiggle the pump wire where the switch lives on the pump from the chassis it might run normal then go back to humming.
I was in a need to use the pump situation and wired directly to the pump bypassing the switch (2 wires on the motor itself +and-). Problem with this is you have to use the switch in your rv to control the pressure. (not good, but works in a bind.)
to further diagnose your pump wire direct to the motor and see if it works. bypassing the switch.
the microswitch is a omron switch that when pressured up opens the contact turning off the pump. they are replaceable for like 10$ on amazon. overtime it looks like water migrates in switch housing and corrodes the switch thus not making proper contact. thus humming begins.
It won't draw enough amps to blow the fuse.My issue was the pump was leaking at its seals and needed replaced anyway so i bought a new 70$ pump. My pump was in a terrible location and i moved it to a easier spot.
Bottomline your buying a new pump or try to dissassemble your pump and replace your microswitch
here is a switch link
microswitchin the picures on this listing you can see one wire comes from pump motor into switch other wire is chassis positive.
