# lacimbali m31 pump



## supersparks (Jun 20, 2012)

hi, all i have recently purchased a m31 dosatron and the pump doesnt run. my question is when should the pump run and what controls it.i have found a pressure switch in the machine could this be the culprit . i am an electrician by trade so please be as technical as you like. thanks, mick.


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## CoffeeJohnny (Feb 28, 2011)

not an electrician, pump should run when you turn machine on, try removing exit hose from pump, disconnect spade connectors to element turn on machine if pump squirts then pump is fine dependent on age it could be a 24v pump and the pump is no longer in production but is available.


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## supersparks (Jun 20, 2012)

geordie-barista said:


> not an electrician, pump should run when you turn machine on, try removing exit hose from pump, disconnect spade connectors to element turn on machine if pump squirts then pump is fine dependent on age it could be a 24v pump and the pump is no longer in production but is available.


as you can proboably tell i am a complete novice to the coffee retail scene .somebody please correct me if i am wrong but as i suspect the machine to work on power up the pump should spin to fill the boiler and pressurise the system, so the pump is either controlled by the boiler level switch or the pressure switch. when an espresso shot is caled for the pressure would drop calling the pump to run again to maintain pressure in the system. so the pump failling to start must be either a pressure stat fault or worse a mother board fault or am i talking utter rubbish


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## MelonCoffee (Jun 21, 2012)

Afraid you could be talking rubbish! The pump runs to supply water to the group at pressure. It may also run to assist filling the boiler when it is below the correct level. The pressure stat is purely for STEAM pressure and not water pressure so that is sidetracking you a bit!

OK there now follows a very simple fault finding guide that I hope will help:

1, connect water and mains check water level in tank (should be 50% - 70%) (if it is low disconnect element to prevent overheat damage to element) or if your machine has an on position without heating you can use that - switch position 1 maybe?) & switch on

2, The pump will not run at this stage if there is sufficient water in the boiler so... Press the button for a coffee - pump should now run. If it does not then is power being supplied to the pump motor? if yes most likely fault is that the pump head is seized - solution = replace pump head. If no power to motor then likely problem on the mother board (check for fuses on board)

Finally, if there is power to the motor you can disconnect the pump-head from the motor, both motor and pump head should be able to be turned by hand. Motor very easily and pump-head should have a little resistance. (will be very tight if seized) If they both turn freely and there is power to motor then try the motor capacitor rather than changing the complete motor.

The following may be helpful too:

How a standard traditional machine works: (in simple terms)

Two independent hydraulic circuits

1) fills boiler to set level (50-70%)

2) supplies water to coffee group - this water is heated by passing it through heat exchanger devices that are within the main tank.

Two independent electrical circuits

1) applies power to heating element until pressure is achieved and switches pressure stat off.

2) supplies all the clever electronics for control of level in boiler valve switching and dose reading (if auto dose type machine)


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## CoffeeJohnny (Feb 28, 2011)

not sure if you're aware but the M31 pump is vibratory, don't know if that makes any difference, I'm having problems with mine, the pump runs but nothing comes out.

I've been told there could be a blockage before the pump or perhaps a solenoid issue?

I will let you know once my friend has been round to have a look.

Because as I get answers to mine hopefully this can further assist here.


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## MelonCoffee (Jun 21, 2012)

If pump is a vibratory then perhaps you'll have to ignore much of my previous post, however, the advice given applies to most commercial espresso machines. I do believe the machine in question is a M31 Dosatron which is a full size commercial machine and will therefore have a standard rotary vane pump and drive motor. The M31 Bistro is a small machine evloved from the Cimbali Junior.

SuperSparks - If you could let us know it would be great, and once again - good luck


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## CoffeeJohnny (Feb 28, 2011)

ah ok mines the bistro single group, was given it for free as it wasn't working so it's my project at the moment


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## supersparks (Jun 20, 2012)

Hi, my machine is the M31 dosatron 4 group machine with the pump mated directly to a single phase 240v motor so i would imagine it being a vane pump

as i understand it on initial start up if the boiler is empty the boiler level switch will give the cpu a run signal to start the pump and knock off at a preset level . then when an espresso shot is called for the pump should run for a preset time and the pressure is then controlled by the overpressure valve.

if i force the pump to run by applying 240v directly to it i get water coming out of the drain and nothing going into the boiler ,this i expect is not right.


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## MelonCoffee (Jun 21, 2012)

If you apply voltage to the pump it runs - therefore, I would suggest you are not getting power from main board. I think you still might have some problems understanding the workings of the machine though. You are likely to get water from the drain without tank filling due to solenoid valve not being open (either on group or on tank fill) Pressure (for the espresso) is NOT conrolled by the over pressure valve. Pressure is set on the pump bypass (should be set at 9 bar) Boiler level switch has a delay start (usually 4 seconds) to prevent constant on off of pump. As for pump running for pre-set time on espresso shot being called for, this again is incorrect. The pump will run for as long as the espresso shot runs for, it is the volume of the shot that is monitored by CPU by use of flow-meters (one for each group). As suggested in one of my previous posts on this thread check the main board for fused output to pump motor. The only other thing that might cause this might be if the level probe is shorted to earth (chassis) - this will cause the CPU to assume that the boiler is full. Thus, pump wil not 'kick' in.

Keep in touch with your findings, will always try to help further & hope i have been of help so far!


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## CoffeeJohnny (Feb 28, 2011)

Hope u can help me, my vibe pump runs but no water coming out have removed exit hose. Any ideas? Blockage before perhaps? Any help would be appreciated.


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## MelonCoffee (Jun 21, 2012)

Certainly could be a blockage before, unfortunately, not being familiar with your particular model I am not too sure if water is plumbed direct to the pump or if it is supplied from an internal tank. These pumps are a bit temperamental - once they are a little worn out they can give trouble. They even give trouble if they are not left free to move a little - so the rubber mounts are not only there to attempt to soften the noise, the pump needs to move but not too much so finding the right balance can be critical.

Ryan @ espresso solutions should be able to sort you out with a replacement http://www.espressoparts.co.uk even if it is a 24v one


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## CoffeeJohnny (Feb 28, 2011)

Cheers have a friend popping round on Saturday to take a look, looks plenty clean inside, pump kicks in but nothing, hopefully it's an easy fix, I got the machine for free so can't complain


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