Williams Powered Diesel Locomotive

Those look like Weaver not Williams!

The drives tend to have the gear split at the top of the tower where the drive shaft goes in or the axle gears split.

You can get replacement gears from P&D hobby Shop

I just went through my 2 Rail Weaver drives like those and replaced some gears. I have some several Weaver FA engines and have taken all my FA-B units and wired a plug into each end that I run through the end window and plug the B units together for better power pickup from the rails. I leave the bodies loose not screwed to the frame and take extra drives when I go run all day at our garden railway. If one of the chassis binds and a gear splits while I am running all day I can just unplug the unit and swap the body onto a different chassis to continue running. Then I can take the offending unit home and spend a few hours working on replacing the gears. It is handy to have a gear puller to get the split gears off the shaft and mount the new ones they go on very tight. My A units I pull the powered unit out for parts and just ran a plug to run out the end unit to the B unit for the headlight power. Gives me spares. A couple of powered B units pull a very long heavy train no problem.

These are good running engines with care and a few spare gears on hand.

Thanks much for the insight. None of them move more than a few inches now. I'll check gears and P&D.

Your locos are missing the center rail pickup rollers.  So even if you get your gear problems sorted out, they won't run on 3-rail track unless you tether them to another piece of rolling stock like a lighted caboose or dummy unit that has pickup rollers and can get power from the center rail.

Perhaps you can purchase the pickup rollers from P&D Hobby as well.  Definitely early Weaver and not Williams.  My $.02.

You have 3 rail engines. Ignore the previous post,  the center rail pickup rollers are at the extreme ends of the trucks.  They're there due to the drive shaft and universals.  Normally the rollers would be in the center of the truck. They look fairly worn from your pictures,  might have to replace them.

So noted. Haven't had time to explore further but hope to do so in the next couple of weeks. Each car does have pickup rollers and a motor.  Thanks for the insightful input and direction. Will keep you posted.

As I mentioned these run good if the gears do not split. With the wheels off the track/ground rotate the drive shaft with your fingers where it comes off the motor and see if there is any binding or high spots on the chain as it rolls over the gear on the top and bottom this should show you if a gear split or a problem and if the wheels turn.

You can check the motors if the gears are OK by using a DC power pack and touch the DC power to each of the 2 terminals coming off the motor. The motors draw just under an amp under load when running.

Again I have had good success with jumper cables between engines for more reliable power pickup. Yes your center rail pickups look worn as noted but may work if you clean them and add the jumper wires between engines. This is a photo of the small male -female plugs I use through the end window on my Weaver FA engines.  I get them at a local hobby shop ? (no # or name), any plug you can find would work they have these at hobby shops and electrical parts stores. Wired to the power pickups from the rails on each engine I am sure if you wire all your engines together they should run well and if one splits a gear can easily unplug it from the train set till repaired.

If an engine does not run then a reverse board might be gone.