Shurflo pro blaster not sucking very much any more

[GHA]

One of these.
http://www.asap-supplies.com/marine/washdown-pumps/shurflo-boat-washdown-pump-509524
Should self prime up to 2m and used to get going no problem, but now will hardly suck at all.

Cleaned the valves and they look OK, any ideas what might have happened?

Tia


PS. Once it does prime it seems fine, plenty pressure it seems.

 

[TradewindSailor]

The problem is that it takes a lot to suck air --- compressibility and small volumes. Most likely problems:

Dirt in the diaphragm valves .... doesn't take much.
The seal between the body halves is damaged .... try immersing the casing in fresh water and then operate it .... but don't get the pump motor or electrical connection in the water
Air being sucked in before the pump
partially blocked feed .... filter / hose / connections

Good luck ... they are good pumps ....