my 8305 4-4-2 postwar MPC is not moving need help

Chris, your loco isn't Postwar, it came from a set made in 1973.  I started a thread about MPC era 4-4-2's a few weeks ago.  You can find it by searching my posts.  My locos sometimes get into a condition where they take a LOT of voltage to get moving (and then take off rapidly with a jackrabbit start.)  Also, when the motor gets warm the e-unit gets balky and won't change direction.  These conditions often occur when the track isn't perfectly level.  

 

Someone on this forum must know what causes this condition, and how to make these locos run better.  It's a shame too, because they are detailed, affordable, and have good features.

 

In your case I would:

-Make sure the wheels turn freely by hand

-Make sure the brushes, brush wells, and commutator surface are clean

-Make sure the brush springs have the proper tension

-Try locking the E-unit in either Forward or Reverse to see if the motor will run

 

Is the smoke coming from the smoke unit, or the motor?  Please let us know what you find out.  -Ted

Other than what has already been posted, brush spring tension is critical to this type of motor, check downward pressure. Also another known problem is the motor frame staking. The staking on these early MPC steam engine motor tends to come loose. Try moving the motor assembly back and forth by hand (out of the loco body). If it is loose, this will cause the armature to bind when running. A couple of light taps with a small hammer on the side frame studs to tighten them up and will solve the problem.

I'm thinkin brushes and the face of the armature need cleaning.  Replace the brushes if they look short and check the brush springs as well.

I had it all apart and its clean.  took the motor out and cleaned the shafts and cleaned the gears.  it all moves free, I wonder if the tension on the brushes is a problem.  I did not see if the holders that keep the armature in are loose.  I bet that would bind it good.  ill check that. 

 

when I put full power, it budges, but nothing Forward , a tiny budge in reverse, that's it.  the smoke unit because I had full power with no movement produced a ton of smoke!  so I shut er off!  no smoke from motor. 

 

Chris

As has been stated, make sure the copper commutator face of the armature is clean and free of oil and grease, and that the brushes are clean and have sufficient spring tension on them to make good contact on the commutator. Does the motor turn freely when you push the locomotive by hand?

Does the reverse unit cycle properly? To isolate and test the motor, disconnect the 2 male plug leads from the reverse unit and connect one of the leads to one wire from your transformer. The one wire from the brushplate that goes to track power should be connected to the other transformer lead. Turn on the transformer and the motor should run. Switch the transformer wire from one male plug lead to the other and apply power, and the motor should run in the opposite direction. Make sure this works before continuing your diagnosis.

 

Larry

thanks larry!  ill try that.  im going to take her apart tonight and see what the issue is.  maybe I goofed some things up when I had it apart to clean it up. 

 

 

If I am reading the Lionel service manual correctly, the 8305 should have a 2-position reversing unit and a double wound field. It sounds to me like there is a good possibility that both field coils are being energized at once. The result of this would be humming, with the motor not turning. I'd say the leads are probably shorted to eachother. Or both are shorted to ground. If only one was shorted to ground, then it would run in one direction.

I have an 8304 that exhibits this same behavior. Takes a lot of voltage to run, gets warm, and slows to a crawl/stop. It will go if I push-start it, but runs sluggishly. I've had it apart and cleaned the commutator, lubed everything, etc. It rolls very freely so nothing is binding. In my case, I bought it new-in-box just a couple years ago, and it hasn't been run excessively. Is it possible that one of the brushes isn't getting power when the motor gets warm? Bad connection?

 

 

quote:

so the wound coil on the reversing unit needs looked at closely for crossing out. 

Not the reversing unit coil.

The motor's field coil is actually two seperate coils, with four wires coming out of the coils.

There should be two field coil wires going to a single brush holder, These two are sometimes twisted together. Each of the two remaining field coil wires should be going to a seperate terminal on the side of the reversing unit. The wires going to the reversing unit should not touch each other, and must be insulated from the frame.

well all the wires are in tact. there is one wire with a shield coming off the reverse unit and that is frayed on the ends and sloppy. I wonder if that wire may touch the chassis.  im going to test before putting shell back on. then I can tape it up if I need to.