g-scale engines run shakey at times

[tiger88mm]

I have several Bachmann g-scale engines ( 0-4-0,4-6-0, a two truck shay and a heisler ),they start out fine then will start to jerk/sputter for a few feet  then run fine and then starts all over again,track is clean and polished ,connections are tight ,drive wheels and trucks are clean,my other engines run fine with no problems,where do I need to look  or do to make this engines   run  again,thanks-=

[Joe Zullo]

Look to the electrical pickups from the wheels to the motor. They could be dirty or not making proper contact.

[Tom Lapointe]

If all the engines run the same way, you could also have a problem with your power pack or feed lines to the track.  Is this an indoor or outdoor layout, & what type of track?  In addition to dirty electrical pickups, jerky operation can be caused by poor electrical joints between rail sections.  Watch if the problem occurs over specific sections of track; often the resistance of a poor joint will change as the weight of the locomotive passes over it.  How old are the locomotives? - The Shay in particular?  Early production Bachmann Shays had problems with the electrical pickups overheating & causing the plastic supports to deteriorate.  Best cure is to replace the original equipment trucks with the upgraded die-cast trucks (which come "standard" on the later production "38-ton" (steel-cab version) of the Shay; the later ones are excellent runners.    Tom

[Joe Zullo]

If all the engines run the same way, you could also have a problem with your power pack or feed lines to the track.  Is this an indoor or outdoor layout, & what type of track?  In addition to dirty electrical pickups, jerky operation can be caused by poor electrical joints between rail sections.  Watch if the problem occurs over specific sections of track; often the resistance of a poor joint will change as the weight of the locomotive passes over it.  How old are the locomotives? - The Shay in particular?  Early production Bachmann Shays had problems with the electrical pickups overheating & causing the plastic supports to deteriorate.  Best cure is to replace the original equipment trucks with the upgraded die-cast trucks (which come "standard" on the later production "38-ton" (steel-cab version) of the Shay; the later ones are excellent runners.    Tom

I guess you missed this part of the OP.....

"...my other engines run fine with no problems..."

[Dave]

You need to tell us, What power supply you are using, What are the other Locomotives and if you are using Linear or PWM.

                Dave

[Loco Bill Canelos]

Tiger, I am sure we can help if we can isolate the many possible problems.  How long has it been since these engines were last run before the problems began,  Did it happen suddenly? Did they all work fine the last time you used them? Also let us know the grades you are operating on and better yet a video of each engine showing the problem.  It is highly unusual for all four of your Bachmann engines to display the same result when they have different pickup systems, especially the shay.

From your description it might be that something is tripping or trying to trip the thermal breaker on you power supply.  Many are thermal and reset themselves.  I have seen this as a cause before so it might be worth checking out.  Another possibility could be a loose wire or connection, but it isn't likely on four seperate engines at the same time.

Bill