Pump stalling at higher preinfusion pressures

Lee Ramseur

Yesterday and today I've been exploring the effects of changing preinfusion pressure whilst keeping dose/grind constant. When going to preinfusion pressures greater than 4.5 bar, the pump sounds like it is stalling.

The pump will activate like normal, and will then turn on/off to maintain the desired pressure for ~10 seconds. After ~10s, I hear a click (which I think is the heating element turning on), then a humming sound, but the pump does not activate to maintain the desired preinfusion pressure. The humming is continuous, until I raise the lever.

After pulling the shot and removing the portafilter, I will do a quick flush to clean the shower screen -- the pump will come on and sound normal. If I pull a subsequent shot, the pump will turn on normally, establish preinfusion pressure, cut on/off as necessary to maintain preinfusion pressure, then eventually do the humming thing. I have noticed that the humming seems to coincide with the heating element turning on towards the end of the preinfusion phase.

If I drop the preinfusion pressure to 4.0 or lower, the pump behaves like normal and will continue to cut on/off to maintain preinfusion pressure, even if I extend the preinfusion time to 20 seconds or longer.

Thoughts?

Reiss Gunson

please post a video of this behaviour if you wouldn't mind lee

if you hold your phone on its side to take the video you will obtain a more pleasing result i think

kind regards

reiss

Lee Ramseur

Reiss,

Here's the video at 5.5 bar preinfusion:


I moved the camera to the inside of the machine in the hopes that the microphone would pick up the humming noise. If you turn the volume up, you'll hear the pump cut on to build pressure, stop, and then stalls with a humming sound that remains constant until the very moment I lift the lever, at which point the pump engages again.

In this video, I pull a shot at 3.0 bar preinfusion (same dose and grind):


In this one, the pump continues to pulse to maintain 3.0 bar, and never stalls (there's no humming).

Reiss Gunson

that's useful lee

can you retake the 5.5 bar shot again, but with the camera focused on the green screen of the pre-infusion module the entire time

you will need to get in close with the camera so the green screen all but fills the frame, otherwise the contrast will be too high and i won't be able to read the pressure numbers on the LED screen

staying back from the screen a little and zooming in will probably work better than getting super close, otherwise i expect it will be able to focus

sorry to be a pain with all these requests, but if i can see the pre-infusion pressure falling below the set pressure and the pump not coming on then we know it is the pump

kind regards

reiss.

Lee Ramseur

Reiss, I'll get the video to you in a few hours -- no problem on the request.

Lee Ramseur

Reiss,

Here's the video you requested:


Prior to shooting this video, I soaked the shower screen in citrus cleaner for 30 minutes. I also set the pump to 100ms. I deliberately let the preinfusion run long (past the first drop hitting the cup) to give the machine the opportunity to stall the pump, which it did.

If you'll notice in the video, prior to pulling the lever the pump stalls at 3.5 seconds (that's the humming noise), then engages briefly at 5 seconds. I pull the lever at 38 seconds and the pump engages without issue until 41 seconds. It stalls at 41 seconds and remains stalled until 58 seconds. It stalls again at 1:02, and remains stalled until I raise the lever at 1:25.

I don't know if this matters, but as a data point the offset when I received the machine was -1.7. I reset it to -1.0.

I appreciate your help!

Reiss Gunson

hi lee

conclusive evidence

you are quite right, i will need to send you another pump as that is a clear malfunction of the pump and explains why it still sour at the high PI settings when it clearly shouldn't need anything like 5.5 bar for the kind of roast you are using

ill book on out on DHL Express later today with a return DHL booking for you to return the original pump to us with minimum fuss

i appreciate that this is very disappointing on a brand new machine

kind regards

reiss

Reiss Gunson

one thing that might solve it is reducing the pump delivery pressure if it is set too high

on the very bottom of the pump, hanging out through a hole in the chassis is a 10mm screw - use an offset wrench or a socket as the screw head will disappear up into the chassis as it reaches the end of the thread, so a conventional flat wrench will not get the job done

try winding the screw fully home and let me know how many turns are need to achieve that

if it is almost fully home already, i.e. less than 1 turn of the screw before it reaches the end of the thread then back the screw out two complete turns

this will allow the pump a little slippage when it is turned on, which will allow the motor to build to full operating revs, and therefore deliver full torque to the pump, allowing it to deliver at full operating pressure of 8-9 bar

if the pressure adjustment screw is turned hard home it is likely to behave in the way you are experiencing

if the adjustment screw is two or more turns out then the pump is most definitely defective

let me know

Lee Ramseur

Hi Reiss,

It took about 4 complete turns to reach hard home. Once there, I backed it out 2 full turns.

I’ve received the shipping notice for the replacement pump - thank you for getting that on the way so quickly. Despite this setback, I am thoroughly enjoying the machine and quite excited for the wireless capability soon.

Thanks,
Lee

Lee Ramseur

Hi Reiss,

I received the replacement pump, installed it, and am now able to preinfuse at 6 bar without issue! The new pump sounds quieter as well.

I did discover what appeared to be some binding of the reservoir outlet connection/pump intake hose when I went to remove the old pump. This may have been a contributing factor to the issue I was having. As soon as I grabbed the hose, the reservoir outlet connection spun free, which reduced tension on the hose. I made sure there was no binding once I installed the new pump.

I searched the site and didn't see instructions or a "how to" thread on LR pump replacement. I did take some pictures to document the process. Would you like me to post that here, as a separate post, or not at all?

Thanks, and I'll be shipping back the original pump today.

Attached files

Dan Tochterman

Hi Reiss,

this 'humming' issue in this thread is very similar to the hum i experience on my machine from time to time. Do you think i should get a new pump when I order the digital infusion kit? or should i try this thread/turn at the bottom of the machine?