Rocket Mozzafiato Evo R | Water flow stops while pulling a shot

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by thm »


New to the forum here, hope I can get some help with my issue. I am the happy owner of a Rocket Espresso Mozzafiato Evo R, so with a rotary pump.

For some time now, the machine appears to have issues when it's not entirely warm. What I do is, I turn on the machine and wait till the boiler hits the right pressure. In the past, I could just grind coffee and then pull a shot without issue. Now, that no longer works, the pressure dial on the right (so the one showing pump pressure) will initially go up to normal value, then it will drop and then it's like the pump shuts down, but you still hear a sort-of static noise/hum. Could be the pump is seizing.

If I just put in the portafilter with filter basket but without any coffee in it, it exhibits the same behavior. However, as I keep trying to draw water by pulling the lever down when the pump seems to seize, and then raise the lever again to restart the flow, it eventually get's better and the pump will seize less and less, almost like it experiences less resistance as the machine and pipes warms up.
And eventually you are then able to pull an espresso shot as you would expect. If I leave the machine on from that point forward, it will work flawlessly for the remainder of the day.

The machine is not connected to the water mains (I use the reservoir). The water is going through a water descaler first, so it holds very little calcium.

Any thoughts on what my issue could be? Pump dying? Solenoid valve maybe? Other components?

I can make a video of the issue if that is helpful.


Weber Workshops: tools for building better coffee
Sponsored by Weber Workshops

#2: Post by JRising »

Can you confirm that the machine, when warming up, is failing to start running the pump motor when you first raise the lever...
Or, are you saying that while pulling a shot the pump and pump motor will stop rotating and all you hear is the hum of the motor?

If it's not strong enough to start up on its own, it is probably a matter of the starting capacitor failing. That capacitor (plastic cylinder wired directly to 2 wires from the motor) is what charges to create the advanced phase and discharges to lag the actual phase so that the motor has a direction to start in.

If the motor is actually failing to keep itself running once started (And is quiet about it), then it's losing electrical power while running. If something was physically interfering with the rotation of the motor or the output flow of the pump, it would loud until it came to a stop.

Need more information. Can you confirm motor is or is not actually turning when it's quiet and pump gauge is at low pressure?

thm (original poster)

#3: Post by thm (original poster) »

It's probably easiest to see it for yourself:
You can hear the 'hum' that remains when the pump shuts down.


#4: Post by JRising »

It may just be the acoustics of the video, but the pump doesn't sound good.

First step would be to monitor voltage to the pump motor, easy enough with a voltmeter right at the white plastic connection on the motor leads. I assume lines voltage continues because I think that's the motor humming like that, but confirming it would be good. Then you can concentrate on the pump.

Second step would be to take the pump out of the machine and feel how it turns in your hands, the "thunk" noise when the machine comes to a stop is concerning. Once the pump is off the motor you'll be able to confirm that the motor spins freely. If the pump doesn't turn smoothly, it might be seizing while running. Strange that it can then start again, but worth checking. You might also run the pump-motor with the pump not connected, just to confirm that it starts nicely and runs quietly without the load.

I don't know what else to suggest, I've never seen that pump and motor slam to a stop like that before except in the case of a seized pump, and that one didn't start up again, it stayed seized. I'm picturing something solid being sucked into the pump and physically bringing it to a halt, I hope that isn't the case, but you're going to have to inspect it unless first step confirms that the motor is being shut off by the control board.


#5: Post by JRising »

New Thought...

It happens most/only when the machine is still not fully thermally stable...

It's happening when the element comes back on while in the middle of a shot. Something is drawing too much power,a short on the powerboard? It doesn't maintain the output. This will be possibly proven testing the voltage at the pump-motor electrical connector.

I think we can rule out that the entire machine is drawing too much... if the entire Gicar were rebooting you'd see that pause before it turned the green light on.

Let us know when you have more info.