There's a part of your pump that holds air. I couldn't find a pic of a wilcox, so let's use the basic diagram at this link...
ram wiki The diagram is on the right side, down a ways. The part I'm referring to is called the pressure vessel.
It sounds like the pump isn't able to open the valve that is marked 5 in the diagram. We know that water is getting in, because you talk about water leaking out the top.
1) Make sure the pressure vessel has air in it. The pump won't work right if it's full of water.
2) Undo the outlet hose (3 in the diagram). Try sending water from the other end and see if it comes out. As mentioned earlier, frogs, etc can clog things up.
3) If the pressure vessel has air and the outlet hose isn't blocked, hook everything back up. If you can put a short piece of hose on the outlet so you can see if the pump starts pumping. Prop the short hose up, pointing in the air. Try running the pump manually. There's a piece that moves up and down or side to side. It's hooked to the waste valve. You probably bump it to get the pump going. Hold it in the up position for 5 seconds, then push it in the down position and hold it there for 5 seconds. Do this over and over and over. Does water come out of the hose? If not, tip the hose over and see if it was even partly full. If this works, you probably need to adjust the weight that pushes the waste valve down, or something was stuck in the waste valve and it needts to be cleaned.
4) If all of the above was unsuccessful, I'm guessing that the check valve is stuck shut or open. or
5) Your ram pump has a leak somewhere past the check valve.
I would expect #1 to be the cause except that it has run fine for 18 months. Usually the air gets absorbed faster than this.
I wish I was close. I like to fiddle with those things.
