Using ue4.7.6 and i do not know how to set up the blueprints for this.
You would probably use an “event hit.” Try out this blueprint: Also create a variable called “Jump Button Down” and make sure its a boolean(red). I don’t know if it applies to you but it worked for me still.
Are you doing a thing where he hits a big step and jumps or like when he falls and jumps? Or other?
Oh I forgot you may choose to enter different values in the jump ZVelocity.