No water coming into the head

[eldiente]

I have a curious problem with my manual head on my sailboat. I have a Wilcox head that is about a 2 years old now. Over the course of the summer cruise it stopped sucking in clean water when pumped with the "flush" lever selected. It will suck waste out of the head but no new water will come in.

I though maybe there was a clog somewhere at the thru-hull or in the hose that brings sea water to the head but everything is OK there. I took the sea-water hose off the head and water came rushing into the boat so no clog there. I also took apart he pump and everything looks in good order there. I thought maybe the seals were worn out but they look fine. Any ideas?

I'm ok with servicing the head but I'm afraid that after servicing it, it still won't work right? The other part of this mystery is that if you fill the head with a bucket of water and pump rapidly the head will begin to draw in sea-water like it is supposed to . This is fine until the bowl is pumped dry and than it stops taking in sea-water. Any help would be great.

Thanks!

-Nate