Morbark Model 200 Help

P

Patrizio

Location
Maine
Hey guys, so I have an old Morbark Model 200 that I bought two years ago and has been running like a champ until the past couple of weeks. Seems to be an electrical issue but could be wrong.

It will run for about 5-10 minutes and then randomly idle down and eventually stall out. It started happening last week. I would get it started, let it idle and then come back in 5 minutes and it would be off. Started it back up again thinking it was just a hiccup and the same thing happened - come back 5 minutes later and would be shut down. Tried to start it again but could not.

I thought it was a lose connection on the back of the switch pictured below so I replaced the wiring on that switch and let her run for 5 minutes and it stayed running so I figured it was good to go. (Obviously should have let it run longer)

Took it out this morning and after 5-10 minutes of it running the same thing is happening. I started it back up again and same thing. Started it again after getting home and even disconnected the wire to the switch to see if it would shut down at that momemt and it did not - it kept running until eventually it did shut down after about 10 minutes. I am dumbfounded as to what the issue is here. Checked oil level, not overheating etc.

Now the interesting part is that if I hold the switch to the right and start it up it will continue to run until I let go of the switch .. So theoretically I could hold the switch for 8 hours and the chipper will continue to run so obviously the switch is overriding something. Does anyone know what this switch is correctly termed or what it's function is? Thanks!
 

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That switch looks to me like a Murphy Switch, which shuts down the engine of the oil pressure gets too low. Make sure your oil pressure is not dropping when the engine warms up, if the pressure is correct you might TEMPORARILY bypass that switch to see if that fixes the problem. If so, replace the switch.
 
Reach said:
That switch looks to me like a Murphy Switch, which shuts down the engine of the oil pressure gets too low. Make sure your oil pressure is not dropping when the engine warms up, if the pressure is correct you might TEMPORARILY bypass that switch to see if that fixes the problem. If so, replace the switch.
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Any idea where oil pressure should be? It is a Cummins 4B. I have gotten different answers all over the board even from Cummins themselves. It sits around 50 psi. Thanks so much!!!
 
Reach said:
That switch looks to me like a Murphy Switch, which shuts down the engine of the oil pressure gets too low. Make sure your oil pressure is not dropping when the engine warms up, if the pressure is correct you might TEMPORARILY bypass that switch to see if that fixes the problem. If so, replace the switch.
Click to expand...
I also just checked the oil and added some as it was a bit on the low side but obviously didn't fix the problem.
 
Thanks for all the replies! Is a murphy switch something I can get at like a Lowe's or Home Depot? NAPA? Or is it something straight from Morbark (I doubt they sell this exact switch as the chipper is 1988)
 
Patrizio said:
Thanks for all the replies! Is a murphy switch something I can get at like a Lowe's or Home Depot? NAPA? Or is it something straight from Morbark (I doubt they sell this exact switch as the chipper is 1988)
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Napa should have it
Or Cummins but I would take the old one to match it up
 
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Patrizio said:
Any idea where oil pressure should be? It is a Cummins 4B. I have gotten different answers all over the board even from Cummins themselves. It sits around 50 psi. Thanks so much!!!
Click to expand...
Not sure exactly, but 50 psi is plenty. If you said 15 I would worry, but 50 is good by any standards, at last as far as the Murphy Switch is concerned. And no Home Depot won’t have one, but Napa or a decent independent parts supply may. Also check out local equipment suppliers or tractor dealers.
 
You can likely find a part number on your Murphy switch, a Google search should find you a few options to buy from. I found one searching my part number a while back for about $150 if I remember correctly
 
So an update: I just started it up again and sat there the whole time paying attention to the gauges. It seems that if I let it sit and cool down it will start back up just fine and then give it 5-10 minutes and the gauges all start going wonky / vibrating until I hold down that murphy switch.

It almost seems as if the switch is working because if it were not why would everything be fine when when I press it? Maybe I don't understand how a murphy switch works. Anyways, the gauges start going wonky / vibrating and then it starts to shut down when the gauges vibrate enough to hit the shut off point but it is due to them vibrating in the first place. It is almost as if nothing is actually wrong with the machine but something is making the pins on the gauges start to vibrate after 5-10 minutes. I've attached a video to make more sense.

In one of the videos the gauges just start go wonky / vibrate after 5 minutes or so of it running.

In the second video, you can see how the machine has now begun to shut down and I can hold the murphy switch in and it will continue to run fine.

Just figured I'd give some more details. Thanks!


 
So it almost seems like it is something other than the murphy switch causing the gauges to start vibrating after 5-10 minutes. I am dumbfounded.
 
Patrizio said:
So it almost seems like it is something other than the murphy switch causing the gauges to start vibrating after 5-10 minutes. I am dumbfounded.
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Just a guess here, but very few wires will go to every gauge. I'd check your power coming in and your ground for good clean connections.
 
I have used the same machine for about 8 years at my old job. The wiring panel can vibrate like hell, there might be a break in one of the sensor wires grounding it to the engine. If the gauge goes bad and the needle bounces it can read like a overheat or low/high oil pressure.
 
Ya the thing I don’t understand though is why after 5-10 minutes? And it’s like clockwork every time. Same exact thing every time I start it. I’ve started it about 15 times now. Runs good for 5 minutes and then gauges start vibrating. Thanks for the replies!
 
It sounds like your engine temp may be higher than it should be causing the Murphy switch to shut the engine down.

I had this happen on my old bandit chipper (John Deere diesel).

The gauges showed the temp to be ok but the machine would shut down after 5-10 minutes unless we held the button on the switch down.

Turned out to be the thermostat on the radiator. Found out after replacing the Murphy switch
 
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