MTH K4 shuts down in same spot

Are you sure both pick up rollers are working properly? One of pick up rollers had a loose wire so it was "dead". It came loose at the wire nut. 

To easily test rollers start engine and idle on a straight trac section. Gently lift front of loco just enough that roller is not touching track.  Then lift the back and test. If one of the rollers are ar not working the engine will shut down fairly quickly.

I've had similar problems with certain MTH engines. The roller size and spacing is different from engine to engine as we all know. I've been finding that some rollers make contact with an outer rail on a frog section of the turnout. Stops them cold. I've been putting a piece of electrical tape on those spots and the problem generally solves itself. The trick is finding which roller is making the contact.

When the engine stops, is it also causing a short?

If so, see Roger's post above mine.

If not, either both pickup rollers are landing on insulated center rails or all of the non-traction tired wheels are on outside rails that lack Common. If the tender has wipers on the trucks to pick up Common, the problem is more likely due to pickup roller spacing.

This is a #6 Atlas right hand turnout.  As installed the turnout opens to my right.  The common rail is away from me (to the outside).  With a voltmeter I found the following:

1. The points are electrically active common to powered center rail.

2. On the next section of rail (locomotive is in the turnout) the fixed outside rail that guides the locomotive through the turnout provides no ground.  

3. At the next section, where the outside (dead common) rail abuts the right-hand guide rail for the straight thru track, the ground is again present.

I assume that the fixed outer rail described in #2 above is supposed to provide a common (it's a long piece of rail on this turnout).  The K4 has two pick-up under the locomotive and wipers on the tender.  All 4 of my other diesel locomotives pass thru this same turnout no problem.

Rick,

One more time...

As previously described, the K4 shuts down as though I had pulled the plug on the power supply.  No short circuit.

Rick,

the K4 shuts down as though I had pulled the plug on the power supply

Are you saying that power shuts down, or that there's still power in the tracks but the engine shuts down?

Power to the track remains.  The K4 shuts down.

Rick,  Start by checking for continuity between the 2 center rail pickups of the engine.  It should read 0 ohms.  Then check for continuity between outside wheels left to right.  Again, you should have good continuity.

If not, then a wire may be broken for center rail pick up, or the 2R-3R switch is not wired right if this engine is 2R-3R and there is no continuity between outside wheels when in 3R position.

Next, back the engine through the switch until it stops and mark where the center rail pickups are, and where the outside wheels are.  Check those areas of the track for continuity and cleanliness.

Most likely you have a dead spot on the turnout preventing power getting to the engine.  You need to determine if this is center rail or outer rail loss.

I believe folks with Atlas tend to add jumpers to ensure power across the switch.  G

Atlas turnouts are notorious for this.

As Jeff suggested I checked the pick-up rollers by lifting them off the track one at a time.  The locomotive kept working.  Is it possible that the spacing is too short between the pick-up rollers for this turnout?  They are only 3" apart where they contact the track, and their isn't a pick-up roller on the tender (just wipers on the axles).  

As the locomotive backs up it appears that the rear roller is momentarily sitting on a neutral rail at the same time the front roller comes into contact with an insulated frog (hope my terminology is right).

Rick

Rick,

As the locomotive backs up it appears that the rear roller is momentarily sitting on a neutral rail at the same time the front roller comes into contact with an insulated frog (hope my terminology is right).

That would cause a stall for sure.

I have the earlier PS2 RK Imperial version of this engine and had stalling issues when traversing multiple back-to-back Ross switch tracks. I added a pickup roller to the tender and that solved the problem completely.

Hi Barry

How would I go about adding a pick-up roller to the tender?

Rick,

How would I go about adding a pick-up roller to the tender?

You would first have to find a suitable pickup roller assembly. I used one from a K-Line caboose that worked extremely well.

Next, you would have to mount it on a tender truck. I was able to remove a screw that holds a side frame on the truck, line up a hole in  the pickup roller assembly and put the  screw back in to secure the assembly.

Lastly, you would have to remove the tender shell, insert a wire from the pickup assembly through the tender chassis and splice it into the wire from the tether that connects to the engine's pickup rollers.

Replace the tender shell and you're done.

Thanks Barry.  I will see if I can locate a suitable roller.  This set has the wireless drawbar, so I'll need to see if I can determine where power is fed back through to the Locomotive.

From what I read here specially "2." you do not have continuity of BOTH outside rails to "common" through the switch. So if I am in fact reading correctly jumper these outside rails together and try running engine the switch.