I had a bad filter this spring. Turns out that the rubber seal area was bent slightly (probably in shipping)It was sucking air and would not prime. I Bypassed the filter to get by for the weekend. When I got home , I placed the filter on the table and noticed when
I picked it up, the wet ring from the oiled seal area only left a ring on ~ 3/4 of the ring. (Took back to where I bought it and they replaced it) 