Checking to see if the air hole in the smoke chamber is clogged is a great idea, but you need to know where that is. It’s located underneath the chamber. Use a a toothpick to clean out the airway. The piston that goes up and down is what pushes air through that little hole which in turn pushes the smoke out of the smokecstack. Also, do not put in too many pills. This will not allow the heating element to heat up correctly to the proper temperature to get it hot enough to generate the smoke needed. I recommend putting the locomotive on the track, turn the power on the track enough to cycle the E-unit into neutral, then turn the E-unit off to stop the humming noise, and then turn the power all the way up to the maximum. This will then make the heating element get to a good heating temperature to start producing smoke and burn off any excess smoke pellets you may have in the smoke chamber. If you start seeing and smelling smoke, manually move the locomotive back and forth on the track making sure the wheels are turning in order for it to move the smoke unit lever, and then to see if there’s any smoke puffing out. This will be a good test to see if your smoke piston is working properly to push the smoke out before you start taking anything apart to clean. If it starts to puff out smoke, you’re good to go then. If not, then you will have to take the boiler off and do a little preventative maintenance on the smoke unit and check to see if everything is in motion with the smoke unit lever, the piston moving freely up and down, and check to see if the air hole is clogged underneath the smoke chamber. Try the simple way first, then go from there. I usually found that excess smoke pellets usually needs to be burned off. Lionel built a quality smoke unit back in the day that’s pretty fool proof, but you never know. Let us know how you make out.