I acquired a z scale collection(small) and two of the locos do-nothing when put on powered track. The third loco runs on track so that part of diagnosis is eliminated. Are there any steps I can do to get these locos going or is it something left to a service place if there are any you recommend?

For HOS I usually remove the plastic body and blast the gearing with CRC contact cleaner until it gets running then give it a drop of train oil on the gearing points of contact.
If the nonworking engines have pantographs then its possible that the selector switch is in the wrong position.
See the respective marklin instruction sheets for oiling & switch location.
-George

Do not use any contact cleaner on any plastic shells. Remove painted metal shells as well.

This is what I use- http://www.homedepot.com...leaner-02130-6/202262505
You should read the specs for whatever product your using.
Lights not working could be a bad bulb or an open circuit. Do you have the model numbers or a photograph of your locomotives?
If you have the body shells off, then photos of the frames might point to something amiss.
George

Edited by user 24 February 2016 02:56:00(UTC)  | Reason: Not specified

It might be quicker to post a photo as a lot of members here are very good at identifying marklin items.
www.zscale.de has lots of marklin photos and catalogs, as well as www.marklin.de