Is it the grind or the pressure?

[Marc1]

Hi there!
I have been playing with the Rossi grinder to get the right grind for my two head machine.
Going by the numbers on the wheel (not that they mean much but just as a guide) it seems that the optimum is between 50 and 60.
Now what seems a bit concerning is that after packing each load in the same way and making small changes to the grind, the machine goes from pushing water through the coffee at a very similar volume to almost zero, just a few drops taking forever, and then I switch it off.

My concern is that perhaps the pump needs to be cranked up a tad?
Your replies are appreciated.

[Barry_Duncan]

Does your machine have a pressure gauge? If so, what does it read when fully blocked by coffee or a blind filter? That will tell you if the pump works or if there is a blockage.

If plenty of pressure, you are grinding too fine, go coarser.

Barry

[Marc1]

No pump pressure gauge only steam pressure. I did a test originally when we change the pump but not recently.
It just surprises me that the extraction goes from normal to almost zero so abruptly.