My Saeco started stalling when pulling shots about 3 weeks ago. I descaled it and it looks like it's still having trouble. My regular routine would be to tamp the coffee in the pressurized portafilter fairly hard - as otherwise it would take about 15 secs to pull the shot. Now, if I tamp any more than flattening the puck, it takes upwards of a minute.
Hey Kai: The first thing that tripped my yellow-alert (sorry, color is meaningless) was the pressurized portafilter.
If your machine is struggling (and the pump is obviously still working) then your grind is too fine.
Haven't changed the grind?
What is the humidity like where you are?
Has the temperature gone up with a corresponding rise in humidity?
When the relative humidity goes up, so the sticktion increases.
What is sticktion you ask?
Sticktion: a movement or mechanical action sticking due to surface tension of lubricant or small amount of friction.
How does this relate to espresso coffee?
Well, add minute quantities of water(from the air) to finely ground coffee and then pack all this under pressure in a portafilter - the water and coffee combined (before the brew cycle begins) create an environment that inhibits brew water from passing through the coffee puck in the portafilter.
Not sure you believe this?
Ask any barista about how warmer weather and/or humidity effects shot behavior in espresso machines. It is dramatic in the cafe and in the home.
Agree - humidity is a likely 'culprit,' requiring you to back off the grind. It really can make a huge difference in how finely you need to grind the same coffee. It can be a great friend for people with grinders that tend to 'bottom out' in the winter, when they can't grind finely enough.
Try grinding more coarsely, and see if this solves the problem. Aim to keep your tamp and other variables the same, and adjust the grind until you reach results in your expected range. Fine-tweak from there for taste. The amount of coffee that you need to dose may vary as well, as your grind and humidity levels change. Shoot for maintaining the same level in the basket after tamping, at least for starters, which likely means a bit less coffee than you were using at a finer grind.
Thanks once again, Colin and Dave, you guys are a cornucopia of coffee knowledge [grin].
I hadn't changed anything else which was what made me ask. The humidity here (Markham, ON) has been quite high in the past few weeks so it sounds like your diagnosis is on. I had thought that maybe my pump was going wonky but I usually run water through the PF after I pull a shot to rinse out all the internals in there and the water only cycle was exactly as before.
I have a low end burr grinder (Cuisinart) and would have thought that the grounds would never have gotten too fine - especially since I was averaging 15-20 secs for a pull in the winter and I was pretty sure I was tamping at higher than the recommended 30 lbs.
I'll try backing off on the grind. Thanks again for the education.