I have the same question. I received mine secondhand as well, and I have no experience with a new one to compare to. It seems to work, but I wonder if it's working well or just limping along. I think mine is ok just going by youtube videos: https://youtu.be/aBYmRHK9BJg and https://youtu.be/ju2GEvlE0hg
Try removing the filter and pushing water into the line with a turkey baster or similar. Or remove the back, hold the line towards the ceiling higher than the pump to allow air to escape and gravity to help. Tap the line and pump to make sure all air is out of the line. There still might be some inside the pump. The pump does not like to be dry.
Quando isso acontecer, você poderá ver um gráfico da reputação que ele adquiriu ao longo do tempo.
Aqui está uma prévia de como será o gráfico:
Nenhuma reputação adquirida ainda.