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Lelit PL41 do I need a new pump?
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Discussions > Espresso > Machines > Lelit PL41 do...  
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yhager
Senior Member


Joined: 7 Sep 2011
Posts: 7
Expertise: I love coffee

Posted Wed Sep 25, 2013, 7:48am
Subject: Lelit PL41 do I need a new pump?
 

Hi,

I'm losing pressure mid-shot, and the pump seems to slow down for a few seconds, then it picks up again. Sometime I'd get a full shot without issues, sometimes I get a few of those fluctuations in the same shot. I've descaled twice last week, but it didn't help much.

Do you guys think I need a new pump? the machine is 3 years old.

Here's a video of a shot I took this morning: http://youtu.be/UxFISQzv8u8

Thanks!
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calblacksmith
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calblacksmith
Joined: 25 Nov 2007
Posts: 7,947
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Wed Sep 25, 2013, 9:38am
Subject: Re: Lelit PL41 do I need a new pump?
 

I watched the video, and I suspect that you are correct.

Normally, when the pump goes quiet, it is due to a build up of pressure but your gauge shows the opposite. It is not cutting on and off, but pulsing so I suspect a wire / connection is not to blame.

If the pump is sucking a vacuum it is possible to act this way, is the pickup tube from the water tank cut at an angle or does it have a V notch cut in it? Is it possible the pickup tube is being pulled against the side/bottom of the water tank and blocking the flow? That sounds like a more logical explanation than a bad pump, most often when they fail, they just slow down or drop in pressure, it is crud in the valves that keeps the valves open so the pump can't move water.

The more I think about it, a collapsed tube or blocked pickup sounds more logical.

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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Frost
Senior Member
Frost
Joined: 26 Jul 2007
Posts: 2,105
Location: Sierra
Expertise: I love coffee

Espresso: Isomac Venus
Grinder: Lelit PL53
Roaster: Poppery I w/variac, MET, BT
Posted Wed Sep 25, 2013, 11:10am
Subject: Re: Lelit PL41 do I need a new pump?
 

Check the spade lug connections to the pump that they are clean and tight. There is alot of vibration that can cause fatigue and could cause intermittent resistance in the connection. Strange behavior indeed.
+1 to checkiing the supply line for blockage. (or maybe an air leak.)
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yhager
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Joined: 7 Sep 2011
Posts: 7
Expertise: I love coffee

Posted Thu Sep 26, 2013, 10:22am
Subject: Re: Lelit PL41 do I need a new pump?
 

Thanks for your responses.

The pick-up tube is cut in a V shape. I've removed the filter that was there originally, to make sure it's not the cause. It's not blocked or squished in any way. I've opened the machine and re-connected the power to the pump (it's not a spade lug type, rather the slide in type, but I've made sure there's a connection).
During a shot I manipulated both the pump connection and the pick up tube and could not find anything that I can do that has effect on the pulsing. I'm not sure how to check for an air leak, but the pickup tube looks whole and clean.

The pump behaves well when there's no coffee in the portafilter, i.e. it only starts pulsating when there's something to push against. I even found that a different type of coffee would make the pulsating less severe. I was even able to pull the odd shot without any pulsating at all.
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Frost
Senior Member
Frost
Joined: 26 Jul 2007
Posts: 2,105
Location: Sierra
Expertise: I love coffee

Espresso: Isomac Venus
Grinder: Lelit PL53
Roaster: Poppery I w/variac, MET, BT
Posted Thu Sep 26, 2013, 3:03pm
Subject: Re: Lelit PL41 do I need a new pump?
 

I'm stumped by the strange intermittent behavior; maybe it is trying to tell you to pull shots at 8 bar rather than 12. Ha....  (should be set by OPV at 9-10 bar range)

Just more guessing as I've never seen such:

You can check if the OPV discharge flow varies. (is there more discharge when pressure drops to 8 bar?)
Maybe there is a bit of debris interfering with a check valve in the pump.  (like a water softener bead...)
If you have a volt meter, check that voltage to the pump is steady during the event. (careful live wires)
If there was an air leak in the input tube, you should see air bubbles flowing into the pump when it is on.

I will be interested to find out what is causing your problem there.
Good Luck.
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yhager
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Joined: 7 Sep 2011
Posts: 7
Expertise: I love coffee

Posted Thu Sep 26, 2013, 3:14pm
Subject: Re: Lelit PL41 do I need a new pump?
 

Whoa! based on your message, look what I found: Click Here (cremina-endo.blogspot.ca)

Looks like I got myself a small project now.

I'll update here..

Thanks!
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calblacksmith
Moderator
calblacksmith
Joined: 25 Nov 2007
Posts: 7,947
Location: Riverside, Ca, U.S.A.
Expertise: I live coffee

Espresso: ECM Vene. A1, La Cimbali M32
Grinder: Azkoyen Capriccio, Major
Vac Pot: 40s era Silex
Drip: Msl. Com. brewers
Roaster: gave it a try, decided no
Posted Fri Sep 27, 2013, 4:39am
Subject: Re: Lelit PL41 do I need a new pump?
 

Good luck, really, it is not hard to work on these machines, scale is an enemy of every machine. I use Calcinet not citric acid for descaling and I found the use of a ultrasonic cleaner to be a huge help in cleaning things up. I know Harbor Freight has a sketchy rep at best but the heated cleaner they have is reasonably priced at about twenty bucks, if I remember correctly. Check out my M32 rehab thread, it shows some pretty bad scale issues, one so bad on the expansion valve (similar to the OPV) that the piston was frozen by scale and had to be pried loose from the grip of the scale. 5 min in the tank with the solution and it was clean as new again without any fuss, muss or scraping.
http://coffeegeek.com/forums/espresso/machinemods/642550

 
In real life, my name is
Wayne P.
Anything I post is personal opinion and is only worth as much as anyone else's personal opinion. YMMV!

Feed the newbs, starve the trolls and above all enjoy what you drink!
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Frost
Senior Member
Frost
Joined: 26 Jul 2007
Posts: 2,105
Location: Sierra
Expertise: I love coffee

Espresso: Isomac Venus
Grinder: Lelit PL53
Roaster: Poppery I w/variac, MET, BT
Posted Fri Sep 27, 2013, 2:38pm
Subject: Re: Lelit PL41 do I need a new pump?
 

yhager Said:

Whoa! based on your message, look what I found: Click Here (cremina-endo.blogspot.ca)

Looks like I got myself a small project now.

I'll update here..

Thanks!

Posted September 26, 2013 link

That's a nice quick under-the-hood tour of this machine you found there.  I have always been confounded by the brew water path on this one.  (vs. machined into the grouphead/boiler bottom.)

While you are cleaning up the OPV, might as well set it for 9-10 bar brew pressure.
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yhager
Senior Member


Joined: 7 Sep 2011
Posts: 7
Expertise: I love coffee

Posted Mon Oct 7, 2013, 5:03pm
Subject: Re: Lelit PL41 do I need a new pump?
 

Sorry for the long delay. I wanted to see how the machine behaves after a few days (read: I didn't want to jinx it).

So I've performed the exact procedure described in the link I sent in my last message. While my OPV didn't look even close to the one in the link in terms of scale, I did clean it up properly, lubed it and put it back. I also took the opportunity to adjust it to 10 bar (it was previously set at 12).

It seemed like the problem is now fixed. Now pressure swings anymore. I think that if the OPV has friction, it takes more pressure to move it, but once it is moved, it takes a little while to go back, so you get the swinging effect, instead of stable pressure.

Thank you all, I have a bit more understanding about how coffee machines work, and specifically mine, which is a great feeling.

I now have a different issue - since the fix, the pump is heating up to the stage where it doesn't work anymore (low humming noise, no water movement). If I let it cool down a bit, it works again. Not sure what to make of it, and not sure if my tampering caused this somehow, or the pump was already tired when I started.

I think I'll get a new pump anyway, but I'm glad I fixed the OPV first, cause it would have been a bummer to replace a pump and not having the problem fixed.

So again, thanks!
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alanfrew
Senior Member
alanfrew
Joined: 19 Dec 2001
Posts: 643
Location: Melbourne
Expertise: Professional

Posted Tue Oct 8, 2013, 1:07am
Subject: Re: Lelit PL41 do I need a new pump?
 

Solenoid valve, solenoid valve, solenoid valve! Have you ever tried backflushing? All the symptoms you describe sound like a dirty/blocked solenoid valve to me, and all your brew water goes through teensy orifices in the valve.

Alan
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