Bo-Ema 1gp - Pump / motor dead?

[atcrank]

Hi all -

I bought a Bo-Ema 1 group in January. It had had about 6 months use, but was actually about 8 years old (it turns out). Rick Bond (the coffee machinist) did the initial service for me and tested it out and its worked well for about six weeks until today. (Rick let me watch him work and it was great to be allowed to watch him go through the service - I learned a lot. Also got to meet Chris from Talk Coffee). As of today the motor just buzzes quietly instead of being loud and shaking the system when it starts pumping. You still get water into the boiler and out of the group head when you activate the circuits, but I would attribute that to the water pressure in the mains. My guess is that either the pump has seized and the motor can't turn it, or the motor has seized.

Is there any chance that I can just hit it with a spanner in the right spot and have it work for another eight years? Or can I fault-find and try some fixes myself? Or do I need to not pass go, collect $X00 and head back to Rick? Andrew

[MorganGT]

Having never come across a Boema with a vibe pump, I'll assume it has a rotary pump.

Generally when I come across a machine where the pump makes a noise but does not seem to run, my first check is to separate the pump head from the motor by undoing the clamp band on the pump and pulling it free of the motor. Then I try turning the pump by hand via the drive key that slots into the motor - if it is the pump head causing the problem, it will often have damaged/sticking vanes or a damaged bearing that can be diagnosed by the pump being either too hard to turn by hand or exhibiting tight spots where the pump 'sticks' in a particular spot instead of turning smoothly. Sometimes if this is the case the pump can be temporarily fixed by turning it a few times to help loosen it, but usually it will need replacing.
If the pump head feels OK, the next test is to activate the pump motor with the pump head removed. If it tries to start but won't (motor makes a jerk when activated, buzzes but does not turn) it may have stuffed bearings - try turning the shaft (with power off to the machine) by sticking a screwdriver in the slot in the end of the shaft - if the bearings are stuffed you won't be able to turn it. If this is the case and the bearing at the end where the pump engages looks rusty, you may have a leaking pump head (water gets past the seals in the head and gets into the bearings).
If the pump head feels OK and the pump motor runs but does not start with a solid jerk straight to full speed (starts slow and builds speed) you may have a duff start capacitor on the motor. Sometimes if the capacitor is stuffed the motor won't start at all from rest, but if you start it spinning by hand then turn it on it will run, indicating the motor is OK but the capacitor is not providing the extra 'boost' of power required to start the motor from rest.
This is a bit harder to test unless you have a suitable multimeter with capacitance testing (most regular multimeters don't). Generally anything more than a 10% drop in tested capacity on a start capacitor means it will need replacing - most start capacitors on pump motors in espresso machines are rated at 10uF, so usually anything reading below 9uF needs replacing.

I would estimate that of the machines I have come across with this sort of pump issue, I've probably seen 100 seized/sticking pumps for every 1 seized motor, and maybe 5-10 duff capacitors for every 100 seized pumps, so the pump head is probably the most likely culprit.

(NOTE: some external pump machines like La Marzoccos occasionally suffer seized pump motors due to the cooling fan on the end of the motor shaft sliding down the shaft and jamming against the motor mounting bracket, but this doesn't happen to internal pumps)

[atcrank]

Awesome, I'll have a look. Yes, its a rotary pump. Thats great!

[atcrank]

I only made it about half-way through my second cup of Moka pot coffee before deciding it was time to get to Espresso Machine ER, and back to Rick it has gone.