Sorry to revive this thread, but i finally found the solution to this mystery. That silver screw on the back of the solenoid IS AN ADJUSTMENT!!! Don't mess with it unless you want to spend an extra half hour resetting it. What it adjusts is the internal positioning of a tiny metal plunger (for the lack of a better technical name). Since the solenoid is a tiny electromagnet that moves that plunger, that screw determines the force with which the plunger moves the solenoid poppet. In my case the screw was not adjusted correctly, which was causing the plunger to be on the edge of the electormagnetic force the solenoid produced.
What this means in turn is that with each trigger press, the plunger moves very little, with almost no force. By adjusting the screw to the correct positioning you can almost shoot that little plunger out of the solenoid.
This is how i did it:
Take apart the solenoid from the long screw side. You should be left with the plastic side with the wires, the "plunger" , and a little spring. I connected that back to the board, put the grip back, and flipped the solenoid to the side, so i could press the trigger and actully hold and adjust the solenoid screw.
The little plunger should be loosely set inside the plastic part with the wires (electromagnet).
Now if you press the trigger, the little plunger should jump, almost coming out of the electromagnet. Thats the correct setup. If you start turning the screw on the back, it moves that plunger in and out of the electromagnet, and therefore lets you set the force which pushes that plunger out. After adjusting it correctly and putting it back together, presto, my solenoid works again.
