By beloved Rocket Giotto Andrea Premium has started behaving weirdly. I need some help with diagnosis please. I grind (Niche grinder) and tamp (The Jack leveler) as usual (20g) with the intent of getting 1 fluid oz in ~27 seconds, using a bottomless triple basket. The shot starts as expected, after about 1/4 to 1/2 oz, the flow just stops. I can hear the pump still running. I removed the portafilter to try to see what was going on. There was no water coming from the group. I put the lever down and up several times, but no water. Then, eventually, water started flowing again. Next shot, same experince.

Any ideas what is going on here?


Thanks in advance,

Craig

Can you post a picture of the innards of the machine? And a picture of the face?

I've never heard of aRocket Giotto Andrea Premium, Is it something that someone has built using some Rocket parts and some Quick Mill parts?
It's hard to guess what's wrong, but if you let us know what it uses for a pump, what gauges it has reading from what points in the brew circuit, etc. I'm sure someone can offer something.

Here are some photos

And an article for those who are unfamiliar. https://espressovivace.com/archives/lucidcafe/LC22.pdf

Okay, perfect. It looks like a stock Giotto, vibe pump, steam gauge only and with the good Sirai p-stat.

If the pump's sound goes much quieter at the point where the flow abruptly stops, then it's a matter of an old pump getting weak. Especially if that is the original pump that was installed back in 2009 at the factory. 12 years is a decent lifespan for a vibe pump.

If the pump's sound stays almost the same at the point where the flow abruptly stops, then it could be a very sticky OPV/Expansion valve that isn't opening until well over 9 bar, but once forced open doesn't easily spring back closed to force the flow through the brew circuit. This is much less likely than a 13 year old pump being weak.

If you brew against the blind filter, does it stall the pump or does it flow well and return over the OPV to the receiver?
Hint: You can run the machine like this with the top off and the reservoir out so long as you keep some water in the receiver(white cup under reservoir), top up the receiver with a bit to replace the amopunt taken to fill the group-head's preinfusion chamber and blind basket... If flow is passing over the OPV, you'll see the water swirling in the receiver because it's returning through one of the ports on the side).