# Pressure too low?



## narc (Apr 25, 2013)

With every coffee I have tried so far with my gaggia classic the only way I can get a shot with the flavour of the coffee coming out is if I grind so fine that any more than slightly more than that weight of the tamper when tamping causes the machine to choke with 14g. A long way off 30lbs of pressure. This isn't a huge issue, I just need to be very careful tamping I don't get channelling but this can't be typical.

Is the pressure too low? It is about the only thing I can think of. Unfortunately I have an old portafilter so the OPV pressure test can't be done without buying a new one plus parts.


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## El carajillo (Mar 16, 2013)

Has it been descaled? ,have you had the shower plate off and the disc behind and made sure it is all clean. If it has recently been descaled it is possible there could be a flake of scale partially blocking the solenoid valve and restricting the flow as the ports in the S/valve are very small.It could be low pressure from over pressure valve " OPV" but these are usually set too high not too low . Does water flow copiously and freely without the PF in place?? Does water flow freely through the steam pipe when switched to water ?


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## Neill (Jun 26, 2013)

What sort of beans are you using and how fresh are they?


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## narc (Apr 25, 2013)

Taken the shower plate off and it is clean I can't work out how to get the disc behind the shower plate (undoing the two allen bolts did nothing?)

Water flows out of it fine as far as I can tell, not sure how you do that from the steam wand

I descaled it a couple of weeks ago, no difference

Beans have been rave signature blend, Etheopian Yirgacheffe and Brazil Santos (latest roasted was 2 days)


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## El carajillo (Mar 16, 2013)

If you take out the two allen screws put the end of the key or a screwdriver in one of the holes andmove it side to side and back to front it will only be stuck, there is nothing else holding it.

To run water through the steam wand put ALL three switches down and open the steam valve, you should get a good jet of water come through.

If your beans are so fresh it is not that causing the problem.

Where abouts are you ? PS you can run water through the s/wand with the disc and plate off it does not matter, also check for flow through the single feed hole behind the shower block.


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## narc (Apr 25, 2013)

One of the allen screws was stupidly tight, the part just would not budge no matter what I did (hope I never have to change the seal...)

Good jet of water comes through the wand (silva wand)

This is quite an old classic. I may mess about with the OPV valve setting.


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## Kyle548 (Jan 24, 2013)

You might have an issue with scale, might be worth disassembling and soaking.


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## jonners (Apr 26, 2013)

Have you tried backflushing with Puly Caff or similar? When backflushing, you should hear a change in the sound of the pump after about 5 seconds, when it begins to labour. Then when you turn the pump off there should be a strong spurt of water ejected into the drip tray. Absence of those signs suggests pump pressure is too low, I believe.

I recently had a problem with intermittent loss of pressure, and a combination of descaling and backflushing seems to have cleared it.


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## El carajillo (Mar 16, 2013)

The ports in the solenoid valve are very small If you have a particle of scale floating about when the pump operates it is possible that a particle of scale is moving and partially blocking one of the ports. IF the solenoid is partially blocked the only answer is to remove it and disassemble it and carefully clean it out. You can try the OPV but I do not think you will find that is the problem unless there is a particle of scale holding the valve off its seat ,the pressure is usually too high not too low. The ULKA pumps are usually very reliable.

Try lifting the pipe from OPV out of the tank and place the end into a glass on the tray ,fill PF with coffee and operate as making coffee ( it doe not need to be hot as this is just to check for flow through OPV ) IF it flows freely ,the pump would appear to be OK, then it is either scale/low pressure setting on OPV OR a blockage in the head behind the stuck plate .


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## narc (Apr 25, 2013)

I have backflushed it with Puly Caff every few weeks. OPV adjustment seems to make no difference at all. Water flows OK from OPV pipe.

I guess a stripdown is in order


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## rodabod (Dec 4, 2011)

Measure the pressure.


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