Lionel 6-11208 LM Big Boy

Its sounds like the cherry switch is either bad or out of adjustment. Some folks have had good luck bending the metal actuator arm down so it makes better contact with the cam on the axle.

I believe the cherry switch on this model is mounted in the top of the front set of drivers. You'll need to remove the front set of drivers to get at it.

Heres the parts listing for that loco: Lionmaster bigboy 

The cherry switch is only $1.50 ,but keep in mind lionel charges flat rate shipping so if theres anything else you need/could use, i.e. smoke wicking etc. You might want to grab that too.

What he said.   Most of these are indeed the cherry switch, and possibly a wire has broken off somewhere as well. 

Awesome, thanks! I completely forgot that I had seen that on some engines. I was starting to think it had some crazy electronic system in place. This makes much more since. Honestly I’m leaning towards a broken wire but worse case I get a new switch. Thanks again!

Try adjusting the switch first.  In many cases, just bending the arm slightly is all that's needed.

Working now thanks for the help. I did bend the arm but also the wire looked kinda chewed up and I accidentally pulled out a splice the factory had in the wire so I replaced the wire also. 

The important question, did it work?

yup and best part I didn't screw anything else up while I was in there.