Mine also has the gauge mounted on the machine and the red pointer does show it sends a shot every once and awhile. What I assume to be the plunger is mounted on the right side of the tank. I'm used to the old oilers with the metal plunger that you could pull straight up to send a shot, this one will not allow me to pull up and all the knob on top of the plunger does is move a little...

How does yours move?