Post By Chris
Bes920 pump prime
My 920 is about 4 yrs old, typical 1 cup per day average. Lately it's started not priming during the pre infusion- sounds a little buzzy when attempting to pre infuse and no pressure, but them when main pressure kicks in its fine. Once 1 shot is poured pre infusion works fine also.
So it's obviously losing water to low pressure pump for pre infusion and needs to be primed with a quick full pressure (usually hold single shot down). Regularly cleaned and escaped. Anything else I can do or 8s it needing a new pump?
Pre infusion works by modulating the voltage to the man pump to produce a lower output. It’s not an ideal way to do if as if you happen to get back siphoning there’s not enough lift to draw water into the pump, particularly in older machines. Why you get this siphoning I’m not sure. Probably air being draw in. Seems to happen to a lot of 920’s over time. I turned my preinfusion off in the end.