La Pavoni Europiccola - Spongy short pulls solved

[nrcoffee]

I just wanted to post this to potentially help out some other frustrated La Pavoni user. I purchased a used millenium recently and almost immediately added the coffee-sensor ppk, sleeve, and all new gaskets. After firing it back up, it seemed like I lost some stroke in the pull. The first half felt spongy, and by the time I'd build pressure, there wasn't much stroke left. So I'd end up with 12-14g in and 18-24g out. But the lever would always pop back up and water would trickle out for awhile after the shot. There was clearly more water left in the group. After reading and reading through a 2015 thread (it's locked, or I would have added this there) about spongy pulls, someone suggested checking whether the lever fork was flipped the wrong way. Sure enough, that was the culprit of the stroke length. 14g in and 30g out this morning and I had to stop the shot rather than just run out of lever stroke. I used a few mini pumps at the top that resolved the sponginess.

[TigerStripes]

I don't understand why it works, but a short series of "mini-pumps" before pulling the shot, also works for me to eliminate sponginess. I have no problem getting a 35-40g shot with a single pull on my pavoni's.

[mwynne]

Can you give a bit more detail? Lever to top, then pump, or pre-infuse first?

[nrcoffee (original poster)]

After it's raised all the way up, I do the mini pumps while preinfusing.

[TigerStripes]

Yep, exactly this. 3 to 5 gentle pumps from the very top of the lever extension, during pre-infusion, and you'll feel the sponginess go away completely.

[Breve]

You might also try heating up the grouphead before you load your portafilter. I have a guess that the brass piston sleeve you added is soaking up more heat than the original plastic sleeve did each time you power up the machine. A cooler grouphead will cause a spongy pull.

Eventually the grouphead will heat up if you leave the machine on for a long time (30min?). If you don't want to wait that long you can cycle the lever up and down before you install the portafilter to exchange cooler water surrounding the sleeve with hotter water in the boiler. This will speed up heating the grouphead. Once the grouphead is sufficiently hot your pulls should feel firm and yield a satisfying amount of liquid per pull (35-45g).

When you cycle the lever you don't need to bleed any water out of the shower screen with each pump. 3/4 length pumps are sufficient. The motion of the piston raising up and down is enough to displace the cooler water upstream of the piston back into the boiler and suck up hot water. I would try starting with 5-6 pumps at a cadence of 2-3sec per pump. Wait a minute after the last pump before loading your coffee and pulling a shot. The goal is to get the grouphead up to the appropriate temp. Not too high, not too low.

All this is made quite easy if you can measure the temperature of the grouphead. I do something like what EddyQ shows here Adding Thermometry to a La Pavoni Europiccola