Need help with smoke unit of Lionel 243 locomotive

I have Lionel #243 locomotive which I purchased on Ebay. The light and motor work well, but the smoking mechanism does not. (It worked for a little while after I received it, but then stopped functioning. I have been using lionel smoke fluid.) I took the locomotive cover off the frame and all the wiring seemed fine. I am wondering if there is anything that I can do to bring smoke back to life again or will it need a new unit? According to what I’ve read, the 243 was only available in 1960 and is identical to the 244. I’ve got the Repair and Operating Guide of Lionel Trains, but the model is not described in the book and I’m not which smoke mechanism could be used to replace it. The bellows mechanism appears to work well when the wheels are turned.