What kind of valve, care to take a picture?
There's only one kind of solenoid where you push the wires in to make the connection.. It's a horrible valve and solenoid
Sounds like you should just replace the solenoid to the valve and re-wire up the connections.
I don't know the exact brand of the valve but it's quite similar to this one..
http://www.youtube.com/watch?v=zCDKA5zD1Uw&feature=related
There are 2 wires that i think is not tough enough,i am very sure that the wires are the ones causing the problem because it runs when i push the wires,so this one cannot be soldered?