Wow it's been a while... 3 kids will do that. hello old friends.

I noticed a few weeks ago that my machine will not build brew pressure. I have it plumbed in and it gets line pressure but nothing else.

It does not appear to be a gauge issue as it responds appropriately when I adjust my in-line pressure regulator. It does not appear to be at the brew group as I completely tore the group down and rebuilt it. I'm getting plenty of water flow from the group, Just no brew pressure. Also, there are NO leaks or opv valves leaking to make me think the pump is building pressure somewhere but is escaping.

The rotary pump is not seized. It turns freely and the motor engages when the switch is flipped and there are no weird noises. As I'm typing this, could it be that the motor engages but it somehow got disconnected from the shaft? I haven't looked to visibly check if the shaft moves when the motor is turned on but will check later tonight if that could be a 'thing'. Also, I've tried adjusting the opv and the pump pressure valves but those don't have an effect.

Based on my understanding of the machine it seems like the pump is the place to look but nothing stands out to me initially on what it might be. My next step is to completely teardown the motor and pump assembly. Anyone have any suggestions on where to look? Appreciate you all.

Even with the brew valve closed or a blind filter in, the pump has no affect on pressure?

I can't imagine how the pump could become unfastened from the motor unless someone who know what they were doing were messing with you and took the little slot thingy out.

Correct. No difference with blind basket in. Still only makes it to 4 bar which is line pressure. Usually I have line pressure set a bit lower at 3 or 2.5 but I let the machine get full line pressure so I can at least have a bit of oomph when trying to make an espresso... yeah I'm stumped.

Since you're getting some pressure, it is highly unlikely that the pump motor has become disconnected from the pump shaft. The way they're built, this is nearly impossible. Before you tear everything down, try this. On the bottom of your machine, locate the bypass adjustment. Put a blind basket in your PF and run the machine, turning the screw to establish which way to turn to increase pressure. Remove the portafilter, turn the pressure up to max and run a bit of water out of the group. Then do the reverse (set the pressure to very low, run water). Then readjust the valve to the pressure you like. Sometimes, a bit of crud can get into the bypass valve that's built into the pump. Moving the valve to its extremes, then closing it back down to normal, can let the crud go by.

Thanks Nunas. I've done that a number of times already to no avail. Tried again just to be sure. I was able to verify that the motor is engaging the drive shaft which would (in theory) be connected to the pump so I'm still left baffled...

Convinced there was something wrong with the rotary pump, I ordered a new one. Turns out that was it! I haven't taken the old pump apart to see what the issue was, but I hope to in the coming days. If I find anything interesting I'll let you all know.