ULKA EX5 pump not working on an Elektra Semiautomatica

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
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#1: Post by algue »

Three days ago I replaced 48W ulka ex5 pump on my 1997 elektra semiautomatica.
I used the trick that I read in this forum: unscrewed and extracted the pump from the support in order to reuse the old one.
After the replacement all was ok.
I tried to do some coffees and they were ok.
The same yesterday.
This morning, after the first coffee, water is not pumped anymore from the tank. The sound from the pump is the same as usual. It seems ok. The problem is that no water is pumped on the coffee.
Connections seems OK. No leaks.
Anyone has idea of what is happening?
I'm not expert of these vibrating pumps. Can they give cavitation problems as rotative pumps if not completely full?

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#2: Post by civ »


1. From what you are saying and before doing anything else, I would check to see if the original pump works 'outside' the machine.

2. Vibe pumps make a 'very' different sound when they pump without water feed.

So if the sound is indeed the same as when it was working , it may be pumping but the water is not going towards the group.

3. To me (YMMV) the symptoms you describe would seem to indicate a problem with the OVP valve.

If I am correct (probably not, it's just a hunch) you may want to consider taking out your OVP valve to disassemble and clean thoroughly with warm/hot white vinegar.



Someone with more knowledge than I has very kindly pointed out to me that your espresso machine (Elektra Semiautomatica) does not have an OVP valve. :oops:

So ...
1. and 2. still make sense to me.
I think a check for scale on the water path (from the pump forward) is in order.

Sorry for the confusion (lack of info).



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Team HB

#3: Post by cannonfodder »

It could be several things. The pump may not be priming, air bubble in the system, or you could have a failing solenoid or blockage in the brew path. If you disconnect the pump on the output side, then power up the machine and turn on the pump you should get water flowing from the pump. At that point you know it is not the pump so move forward in the system. Check the solenoid and make sure it is opening, check the group for scale or a blockage. The hydraulic system on a Semi is not that complicated so you just start from one point (pump) and work your way to the group until you have no more water flow. Then you know where your problem lies.
Dave Stephens

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#4: Post by algue »

tomorrow I'm trying to look for the problem.
I confirm that the sound of the pump seems good
but I can neither fill the boiler with left button, nor pull a shot with the right one
water level remains the same in the upper tank, indicating that the pump is not working

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#5: Post by algue »

Finally the problem seems to be due to a defective pump.
Today I turned the machine on and the pump worked.
I made a good coffee.
After a while, water flow went down until it stopped.
I decided to install the old pump again.
Let's see what happens.

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#6: Post by algue »

Just to keep you informed, all the problem was due to a small plastic aerator that is placed inside the outlet pipe of the pump.
It was damaged (or I damaged it during the replacement by tightening too much the T-connector ...) and it was obstructing almost all the pipe section.
Now I removed it and replaced it with the one of the old pump
All seems ok now

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#7: Post by civ »


If I may, I'd like to add a bit of information that may be of use to those taking apart an Ulka pump.

From what I have seen, it seems that Ulkas, either in their brass or plastic incarnations, are all more or less the same, save for their wattage.

The brass or plastic I am specifically referring to is the part in the photo below, located at the output end of the pump. On one end it holds an 'O'ring (part 2), a plastic ball and a spring. On the other end it holds parts 3 and 4.

Two screws and a plastic collar hold it in place along with the rest of the pump's innards.

Photo courtesy Rod Schiffman - ulkapumprepair.blogspot.com

The little plastic retainer (3) for the spring loaded plug (4) is quite fragile and like all internal Ulka pump parts, unobtainable as spares. Should you lose or damage it, your only hope is a burnt out Ulka to cannibalise it from.

Great care must be taken to not 'screw it up' (pun intended) as it were by letting whatever attachment goes at this end of the pump (usually a over pressure relief valve or a 'T') too far inside as it will keep the pump from working properly or damage this fragile part permanently.

An after-market OVP I installed in one of my old my espresso machines had too long a thread and I almost damaged this part by screwing it too far inside.

When I took it apart again I verified the depth of the available thread with a caliper (right before touching the plastic retainer) and it measured out to 8.0 mm, at least in my Ulka Model EP5 pump.

So my guess is that 8.0 mm (+ some Loctite sealer) is the actual limit and quite enough.



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#8: Post by algue »

The little plastic retainer (3) was just what I damaged
To overcome the problem I cannibalised the old pump, that had that retainer in good conditions
In my opinion, that part is too fragile
Probably It shoud have been better designed, or it should have been made of metal