Windscreen washer pump

[mauro12]

Hi guys , I’ve always wanted to fix my windscreen washer and I believe is a great weekend work to do . Today I removed the fresh air scoop and I blew some air in the tube and seems to be ok and not blocked . The problem is that there is no suction  of water . The pump is running normally , is not the original pump but is another one from Mercedes , probably from a different model .
My question is , how is possible that the pump motor is running but doesn’t suck water ?
Thank you

[Lorsar]

I found the answer in the forum but I can't seem to find the original thread.  I was able to get it to work by pulling the tube out of the bottle and  pour some fluid (or water) into the tube while holding it up so gravity led it to the pump and then it worked fine after that

[mauro12]

I can visually see the impeller running but I don’t feel any water suction . I will follow your advice and pour some water inside the pump by gravity and check if it works .
This is the pump I have right now .

https://classicmercedesparts.co.uk/products/32046-mercedes-benz-w123-230e-windscreen-washer-pump-1238690021