[Nebe]

Salty, you say the foot pedal makes the solenoid click, so we know the pedal works..then you say that after you click open the solenoid, air rushes out, so we know the solenoid works.
The air that is exhausting is supposed to be going through your piston. The problem is that the air thats rushing out through that fitting is not being pushed down the piston....check to see if that fitting that the air is leaking from is ajustable... if it is , close it up and your piston will move.
if the fitting isnt ajustable, the fittings that screw into the housing might be missing, You will have to find a nut to close it up(preferably the right fitting from the MFG). The deal is that the bleed fitting is supposed to bleed just enough air so your piston moves at the correct speed and pressure.... If the hissing air has a nut and its open a bit, a thing to try is to crank up the PSI before you even mess with that bleed fitting and see what happens... you might have your compressor's PSI set too low and its only venting through the bled fitting..

I know its confusing but I'll anser more questiosn for you as you have them