Rocket Giotto Losing Pump Pressure - Page 2

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#11: Post by wlaughto »

JRising wrote:Sorry for the multiple-post spam, but another thought just whistled through my head...

It is possible on the old Gicar unit that's in your machine for it to try to fill boiler while you're pulling a shot. That Gicar doesn't monitor the position of the lever... One trick to rule out the possibility of the machine trying to "Boiler Fill" while you're brewing is to slightly overfill the boiler right before pulling a shot. When facing the machine, your right-hand side is the side where the boiler's level probe is. Lift the right side of the machine 3/4 of an inch or more up to an inch and a half and slip a cuttingboard or the handle of a kitchen-knife or something under the rear foot to hold it up like that until the boiler finishes filling to its new "slightly overfilled" depth. Then when you set the machine flat on the counter again, there's no chance of it trying to fill the boiler while you're brewing.
Further explanation. When brewing, the pump is forcing the water into the machine fighting against the backpressure of having to force water through the grounds in the portafilter. It builds 9-10 bar pressure to be able to force the amount of flow through the grounds that you see while brewing. If the Gicar decides to do a boiler fill, it opens a valve to the boiler which is only 1.2 Bar of backpressure to overcome, all of the flow takes that nice easy path, the pump noise changes as it overcomes less backpressure and there's no flow through the portafilter.
Does this maybe describe what you're experiencing?
If after doing the "Overfill before brewing" experiment, the problem goes away for a while, let us know. We'll get into cleaning your boiler fill probe and other suggestions that may limit the occurrence.
No 'sorry' necessary. Much appreciate the help. A bit of a novice at this so will be taking on board any info I can get.

Can't look at this today, so will get back with my observations etc tomorrow.

BTW, the reservoir actually has 3 pipes, looks like the 2 you describe + a third which come out of the top of the reservoir, connects to nothing but runs vertically up the side. Also has a small plastic ball running inside of it.


#12: Post by wlaughto »

A couple of photos of the machine and internal reservoir.


#13: Post by wlaughto »

Ok, managed to get to this today. Tried the over fill trick and yes water was coming out of the return pipe. Also made no difference to the operation of the machine with blind filter. Ran correctly for a few seconds, paused for a second and then pump was considerably quieter and not operating properly.

Did this a couple of times and mostly got worse, with the pump stopping for about 2 seconds before starting again (at lower rate), then stopping, starting, stopping etc.


#14: Post by JRising »

Woah, OK. Your machine isn't as old as I expected.
I was expecting first generation Giotto where the hoses came out of the machine and hung into the reservoir from above. Not a problem.

Your photo has captured the OPV. When the pressure in the brew circuit gets above a set limit, it should force past that valve and return to reservoir (Blue Arrow direction).

As a test... With the machine open, reservoir out, and that little white receiver (Cup under reservoir) full of water... Push and hold the button behind the brew lever while the lever is in the down position, for maybe 15 - 18 seconds. This will run the pump with no valves open. This should:

1: Make the pump stall if it reaches it's maximum backpressure and the OPV doesn't let any flow through.

2: Pump all the water over the OPV, which should sound like a quick ramp-up of pressure, then very steady flow as it just circulates back. You will probably see the current flowing in the receiver as it pours back in from that connection on the side.

Knowing the outcome of this test will rule out a lot of possibilities.


#15: Post by wlaughto »

Ok, so did as suggested and basically nothing happened other than the pump running smoothly with a constant noise and no stall for as long as I kept the button pushed in (60 or so seconds). Lever was in down position i.e. not open. The reservoir cup was full prior to testing. There was no discernable water flow back into the reservoir cup from the OPV. The water level in the cup remaimed constant.


#16: Post by JRising »

If the water isn't flowing over the OPV and back to the receiver, then either the OPV is seized or set too high, or the pump is too weak to move the water against a backpressure high enough to brew. Do you know anyone with a gauged portafilter you could borrow? I know you've replaced the pump, was it a pump from a reputable source and the date on the pump newer than 2018, or was it some old stock purchased on Amazon because the price was good? Without being able to test components, and with the possibility of more than one issue (Seized OPV allowing weak pump to stall/go quiet) diagnosing further gets tough.


#17: Post by wlaughto »

The pump was purchased from one of the main suppliers of spares here in Sydney and most reputable. I'm fairly convinced it is not the pump as the new one has behaved idendically to the old one before I replaced it.

Unfortunately I don't know anyone with a guaged portafiller, other than a repair shop. Do you think that the OPV is likely to be the problem if we ruled out the pump or could there still be another component causing the problem? If I were to pull the OPV out, is there any way to test it either visually or otherwise to see if this is the problem?

Given the machine was working at one stage, then the OPV must have been operating at the correct setting. Would this not rule out an incorrectly set OPV (pointing to a ceasure), or can the setting vary over time? How is the setting adjusted?

Also just for clarity, the Over Pressure Value (OPV) you are referring to here and have hilighted in the photo above is a different OPV to the one on top of the boiler? When I Google Over Pressure Valve posts point to the one on top of the boiler.


#18: Post by kitt »

What part of Sydney are you in? i have a pressure portafilter you could borrow, or happy to look at your machine if you can get it to me on the North Shore


#19: Post by wlaughto »

Are - wonderful. I'm in Mona Vale. Where abouts on the North Shore are you?


#20: Post by kitt »

Will send you a PM