Lionel 180w Brick.

Are you saying you have two and both do the same thing?  If so, they're either dead or you are having a meter issue.  Are you "sure" you're meter is actually able to measure AC voltages?  If so, and you are connecting to the only to contacts in that plug and getting 4V, the brick likely has an issue, most likely the circuit breaker circuitry.

I figured it out. If you look at my photo, the port on the right is a NC SWITCH. I frigging switch. It needs to be pushed in. I used a tooth pick to  push it in and I get 18 volts now. I am a frigging idiot!!

Not sure what you did, but as long as it works.

Gun. Take a look at my photo of the Molded plug. There are 3 Ports. Notice the port on the right seems blank. When I test the two to the left, I get 4 volts. BUT, when I stick something into the blank port, it turns on a switch. And I get voltage. 

OK, this is the new brick with the interlock.  A stupid idea if you ask me, but that explains it.  I have a bunch of the older 180W bricks, I don't have no stinkin' switch to screw me up.   FWIW, that also means you have to have a dummy pin on the mating connector to activate the switch.

Gun. My next move is to cut the molded plug right out.