Pump operates, but no pressure/water

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simonella
Posts: 2
Joined: 12 years ago

#1: Post by simonella »

I am wondering what could cause the symptoms I have with my HX machine (with 3-way solenoid valve): pump comes on, but there is no water/pressure at group head, even with portafilter off, and pump is 'quiet' as if it is operating against high pressure - same pump noise as when doing a backflush and full pressure has been reached against the blind basket.

It seems obvious something's preventing the water coming through, but what? Note the problem is intermittent - sometimes the pump works normally with full flow when you switch it on, sometimes it is quiet and there is no water/pressure at group head, and sometimes it's in between - pump is slightly noisy, and there is some water/pressure at group head, but not a lot. It's impossible to predict and can change from one extreme to the other from one switch-on to the next a few seconds later. Doesn't matter whether the portafilter is in place or not, and doesn't matter if machine is hot or cold, though problem is more prevalent when machine is hot.

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HB
Admin
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Joined: 19 years ago

#2: Post by HB »

You didn't mention the specific espresso machine, but it sounds like the brew solenoid is sticking. Scale buildup can do that. If so, disassembling the solenoid and soaking its body/plunger in vinegar would help. Or the solenoid coil could be defective.
Dan Kehn

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allon
Posts: 1639
Joined: 13 years ago

#3: Post by allon »

If you suspect the solenoid is sticking, you can try rapping it gently with the handle of a screwdriver; if it unsticks, then you have a positive diagnosis.
LMWDP #331

simonella (original poster)
Posts: 2
Joined: 12 years ago

#4: Post by simonella (original poster) »

Thanks for your replies - I took the machine to a technician, who diagnosed a faulty pump. Apparently if these machines lie in storage for a while before being sold, the pump can develop a problem. It's a Nuova Simonelli Oscar.

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normriff
Posts: 66
Joined: 12 years ago

#5: Post by normriff »

Storage and improper storage are common causes of service work for me. Even new machines from the factory needed to be bench tested before going to the customer. Eventually the water in the group head evaporates or otherwise disappears, leaving a residue that plugs the jet.
A lot of the machines i see have been subjected to freezing.
Norm Riffle
The Original "It's A Grind", Portland Oregon - Espresso and Coffee Equipment Specialist since 1992