Lionel Post War Steam Engine (1656) Cast

When you put it back on the gear you may have gotten it out of sync with the connecting rod so the wheels will jam up.

pull the rods off, and eye up the wheels. sounds like the loose wheel is out of sync. try adjusting the wheel until it looks the same as the other wheel. then try putting just the side rod (the one that connects the two wheels on one side) and moving the wheels. If there is resistance, see when it happens, and adjust the wheel a tooth on the gear. I've used super glue to hold loose wheels, and others use Loc Tite.

As Steamer has replied, you definitely have it out of sync.  Where the screw hole for the connecting rod is located on the good wheel, the loose one has to be lined up in the same plane.  You didn't specify which wheel came off, whether it was a geared wheel, or the plain wheel, and whether it is the front or rear wheel.  Try to get the screw hole for the connecting rod in a certain location (imagine the face of a clock, with 12, 3, 6, & 9 o'clock postions), and set the good wheel at that location.  Line up the loose wheel to the same location, and put it back on.  Add the linkage, and rotate the wheels by hand, and see if it goes the full rotation, without binding.  If it doesn't bind up, press the wheel back tightly, and put a dab of "Loctite Super Glue" at the axle to keep it on.  You may have to play around a little bit with setting the wheel in line with the existing wheel, but when it is place correctly, everything will work.  Good luck.

Besides what has been already mentioned, the eccentric crank is out of position. It should be pointing slightly off center of the axle. Fix that first. It might be all that is wrong with it. The wheel cannot turn any further counterclockwise in your picture being held in place by the eccentric rod.

Pete

Thanks Everyone.  I will give your idea's a try!!!