Couplers sparking??.

Turn off power to be safe before removing cars.

yes thankyou will do, why would i get sparks, both out side rails should have no voltage right?. somethings wrong ,some where. i would like make it right. just ground( simple ovals of track ). nothing shorting across that i can see.  should  not be any voltage going thru couplers right???. cant be good for electronics in my engine right?.

The outer rails do indeed have voltage on them.  If the loco has poor contact with the outer rails (traction tires, dirt, etc.), there may be a flow of electricity from the trucks of the cars, through the coupler to the locomotive chassis.

Adding to GRAMPSTRAINS' reply, when you pick up a car, the front / coupler end of that truck may move down enough for a part to touch the center rail. As long as there are no sparks when running, the car should be OK.

Somehow one or more of the couplers is connected to the center rail.  I would suspect the locomotive since, I believe, the Menards cars have no center rail pickup.

If you have a volt-ohm meter set it to continuity or resistance; touch one lead to the center rail and the other to the coupler.  If you get a beep, the meter moves or the display is something other than one - you found the problem.  I would suspect a frayed or damaged wire from the roller pickup.

thanks for reply, i ohm the engine coupler to center rail 0 ohm . i ohm both flat cars couplers to center rail i get reading on both very low .130 to .235 on both cars , im thinking ohms should  be 0?. 

also correct no center rail pickup on flat cars, also can not see anything touching center rail.

The resistance from the center rail to the coupler should be very high or infinite.  If there is only .1 ohms between the center rail and the coupler, some conductive part of the coupler has to be touching or connected to the center rail. 

maybe i've got this all backwards , but i believe there should be no reading (0) between center rail and coupler unless there' s  some connection between them. if i ohm positive and neg to center rail close together i get 0 ohms. when i ohm center rail to coupler i get reading of .120 to .230  very low, but any reading no matter how low would indicate there's a connection there. is this not correct?. 

The transformer may be creating a low-resistance path between the center and outer rails if a brick is directly connected to the track.  Otherwise, you need to remove anything with a roller - loco, lighted cars, etc.

You are correct in that there should be no reading between the center rail and the coupler.  You have a reading so something is wrong.  Check the couplers on both ends of the loco.  To Dale's point, do you have this problem with any other loco?

yes DANR last time i've seen sparking was with different engine on different loop with no connection to to this loop ,using only one transformer per loop, again no inter connection between transformers. only similarities that i can think of its happening  when i have these two flat cars. i guess like dale is suggesting i should take off engine and rail cars one at time as i ohm,to rule out other cars?. but im thinking it not other cars or engine being that im getting reading on these flat cars, they have to be the problem?.