Thanks for the replies everyone. This has been a learning
experience. The issue with these pumps is that they use a tiny microswitch to actually switch the pump motor
directly - not through a relay. Yes, an accumulator will help, but the fact remains that they are using these switches way outside of their design spec.
I did an autopsy on the switch and sure enough - the contacts inside show lots of evidence of arcing. I'm surprised it worked as long as it did.
I'm doing several things:
1. Installing a Relay. The pressure switch will only need to energize a 130mA coil now instead of a 20A motor
. The relay will energize the motor (well within it's design limit).
2. Installing a small accumulator.
3. Ordering 10 spare microswitches.
I think I'm covered