I also had an issue with mine sometimes not working..
I pulled the motor off the pump and opened it up.
The armature was really dirty and the brushes were a tad stuck.
I chucked up the armature up in my drill press and cleaned the commutator with a stone for cleaning the slip rings on the onan.
Then cleaned everything else up, the brushes were fine just after inspection.
I put it back together and bench tested the motor and reinstalled.
No issues since that time.
BTW the motor is the same one most pickup truck snow plow lifts use..
Lynn, Guy & Rocky
2004 Monaco Dynasty