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We bought a somewhat unloved 8970 last year to give us some extra tractor for harrowing and such. anyhow it got put on the grain cart last fall and proved itself as a very suitable unit for that purpose. It didn't take long before it developed a rpm surging habit, it also would just quit with no warning but would always start right up. its hard to unload on the go with that going on:D. With a lot of luck we found that by putting pressure with your thumb on the side of the ecm the problems went away. you will see in the pictures that a hockey puck with two quarters taped on the back and held on with a hose clamp solved our immediate problem. we have ran over two hundred hours this way. my question is has any one ever sliced the cover off one of these things? Im speculating that its a lose or broken connection in there and maybe....just maybe it can be carefully fixed. the way it is right now it works. any ideas would be appreciated.
 

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It's a box full of silicone type rubber protecting the circuitry. You'll need a set of special screw drivers to get that far. There is a potentiometer in there that could be your problem.(as soon as i find that info again I'll post a link. I guess i didn't bookmark it). I started to take mine apart but decided against it. I ended up unplugging the harness that goes to the fuel rail sensor and it runs like a top since. I've run with that sensor unplugged for about 4000 of the 5000hrs on the machine.

A new rpm sensor on the cummins side of the wiring, fixed it when it wouldn't idle down. The problem began with the throttle behaving normally when it was cold out or the motor hadn't warmed up fully. When the machine was warmed up, usually after working for a couple hours it wouldn't idle down. After a while it would only run full open, even on start up it would fire up and then hit WOT. scary. What a cluster f those things are.

Post back if you need more info and pictures. The more discussion about that setup in the public the better, finding someone to fix one is a nightmare.

Have you priced out an ECM? Just curious to know what they are worth.

Offroadnt will hopefully check in, he has lots of experience with this fine setup also.

Edit5:

See of you can find a model/part number on your ECM. The number hand scratched in mine took me to www.ambacdiesel.com (formerly American Bosch). That is where I found the potentiometer adjusting info. I've spent weeks searching for answers on this motor!
 

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thanks for the reply! I find it odd that you can unplug the fuel rail sensor and it continues to operate properly! I will keep that in mind. the ecm was priced at approx. $3000.00 last fall in regina. have to chek in minot though. from what your saying trying to take this thing apart at this time isn't a good idea. I will wait to see if some one else puts a post up.
 

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You can also remove JD modified PT pump and put a normal one on. I think there's a few guys on here that have done that.
 

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thanks for the reply! I find it odd that you can unplug the fuel rail sensor and it continues to operate properly! I will keep that in mind. the ecm was priced at approx. $3000.00 last fall in regina. have to chek in minot though. from what your saying trying to take this thing apart at this time isn't a good idea. I will wait to see if some one else puts a post up.
I would wait until you are not busy to tear it apart. That is the biggest reason mine didn't get the treatment, I was using it everyday.

I've also been told that this motor is setup more like a marine/genset motor than a truck motor. The speed sensor on mine had to come from the west coast, it was the only one in Canada at the time.

I've got the electronics testing part of the Cummins manual here somewhere. Let me know if you need it.
 

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The wiring harness's on these..plus the connectors take a beating and cause problems for the Cummin's equipped Deere's

John Deere's 'Century' system allowed these tractors to have stuff like 'field cruise' and such...better regulate the electronic Cummin's engine to dirt-turning rather than over the road use.

The Century controllers can and do go bad..however often it's shot wiring harnesses the crap-out and cause problems
 

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I m just new to the Forum. I found it because I have a similar issue on an 8970. I m looking for a wiring diagram related to the Cummins part of 8970.
A good wiring diagram is always helpful to follow and measure components values. I will follow with my finds and results.
Thanks for any help.
 

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Offroadnt will hopefully check in, he has lots of experience with this fine setup also.
LOL, sounds like you know quite a bit more then me :sFun_whistle:

What I wound up doing was Googling the part number, going on here and other forums just like you're doing and eventually a very fine fellow on Agtalk said he had a used one that he would sell me, I bought it, installed it and it's been working fine ever since.

That being said we did have some issues again this summer, the engine was cutting out, turned out it was a bad connection in the harness plug over the hydraulic pump. I've also had issues with the main harness plug that passes through the floor in the front of the cab left side (It's bugger to get to).

Komatsu65, how on earth did you figure to push your thumb against the side of the ECM like that :44: That was simply genius :54:
 

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I m just new to the Forum. I found it because I have a similar issue on an 8970. I m looking for a wiring diagram related to the Cummins part of 8970.
A good wiring diagram is always helpful to follow and measure components values. I will follow with my finds and results.
Thanks for any help.
What specifically is it doing? They do some weird stuff all caused by different things.
 

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LOL, sounds like you know quite a bit more then me :sFun_whistle:

What I wound up doing was Googling the part number, going on here and other forums just like you're doing and eventually a very fine fellow on Agtalk said he had a used one that he would sell me, I bought it, installed it and it's been working fine ever since.

That being said we did have some issues again this summer, the engine was cutting out, turned out it was a bad connection in the harness plug over the hydraulic pump. I've also had issues with the main harness plug that passes through the floor in the front of the cab left side (It's bugger to get to).

Komatsu65, how on earth did you figure to push your thumb against the side of the ECM like that :44: That was simply genius :54:
I had one of the two rpm sensors on the Cummins side come unplugged the other day while I was washing it. It ran fine for about 5 minutes then revved up to about 2400rpm and died. Wouldn't restart. The connection was hooked back up and away she went..... Man these things do weird ****.

Like a red headed step child, the **** things, piss'yaoff, but'yagotta luv'em.
 

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Here's the thread I started and the successful conclusion. There are are part numbers and discussion you may find useful. Viewing a thread - Where can I find a John Deere/Cummins ECM
Mine was doing exactly what 9670guy's was doing. It would rev and there was no way to bring it down. After several hours of diagnostics it was determined to be the rpm sensor on the Cummins side. There are two in the same fitting and both had failed.

Is that ECM still working for you offroadnt?

These things have just enough electronics on them to make me positive I don't want a more "advanced" machine.
 

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I had one of the two rpm sensors on the Cummins side come unplugged the other day while I was washing it. It ran fine for about 5 minutes then revved up to about 2400rpm and died. Wouldn't restart. The connection was hooked back up and away she went..... Man these things do weird ****.

Like a red headed step child, the **** things, piss'yaoff, but'yagotta luv'em.
LOL, it's a beast :D

It is a good tractor, so far it's been cheap power but you need to grease the axle ends, keep the diff yokes tight, keep an eye on that coupler on the back of the engine and be patient with the electrical system.
 

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It did quit when running warm. Then cooling off it would restart. Then the guy told me it don't restart at all.
I am making a few connectors and will use a slant six distributor to create some impulse and hear if my fuel shut off click or see if 12 volts apear. I have not dig hard into it yet.
 

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It did quit when running warm. Then cooling off it would restart. Then the guy told me it don't restart at all.
I am making a few connectors and will use a slant six distributor to create some impulse and hear if my fuel shut off click or see if 12 volts apear. I have not dig hard into it yet.
That happened to some other guys I know, tractor would just quit, usually it would restart, one time it didn't. A new brain box (ECM) fixed it.

If I get in early enough tonight, I'll see if I can find the test stuff I got form Cummins.

Im not sure if this is helpful to you but here goes anyway


If I recall, you should be able to hear the fuel control actuator humming with the key on and all else off.
 

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I had one of the two rpm sensors on the Cummins side come unplugged the other day while I was washing it. It ran fine for about 5 minutes then revved up to about 2400rpm and died. Wouldn't restart. The connection was hooked back up and away she went..... Man these things do weird ****.

Like a red headed step child, the **** things, piss'yaoff, but'yagotta luv'em.
The 2 sensor . Do you mean on top of flywheel shield ?. My thought , one is John Deere tach siognal ( intrument cluster)
And other would be engine speed to ECU. I have not prove that to me .
Once I use my electronic distributor to test I will find if one is for dash and other for ECU
 

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That happened to some other guys I know, tractor would just quit, usually it would restart, one time it didn't. A new brain box (ECM) fixed it.

If I get in early enough tonight, I'll see if I can find the test stuff I got form Cummins.

Im not sure if this is helpful to you but here goes anyway


If I recall, you should be able to hear the fuel control actuator humming with the key on and all else off.
Thanks
 

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The 2 sensor . Do you mean on top of flywheel shield ?. My thought , one is John Deere tach siognal ( intrument cluster)
And other would be engine speed to ECU. I have not prove that to me .
Once I use my electronic distributor to test I will find if one is for dash and other for ECU
Yes there are 2 speed sensors on the flywheel, one for the Deere side and one for the Cummins side. The Cummins sensor has two sensors in one fitting( two sets of wires with weather pak connectors to the main harness) How is that for keeping it simple.:eek:

I have the test procedures for the sensors at home, it's a simple pass/fail resistance test.
 

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Hi Guys !! Done some homework today, On the 8970 I m working on.
- Relay K4 is ignition relay and sends power to fuse #14
-Fuse #14 that is Engine control. It also feed the field circuit of the alternator.
-After replacing the fuse , I had power with key on one of the pin at one of the two round 9 pin connector
-I finally had starter working acceptable to test my speed sensor at flywheel.
-The one speed sensor to the left ( driver's side) has 2 pair of connectors. Both are engine speed signal to the electronic ECM
- Both were is the 1000 ohm range and made around 1.3 ac volt engine cranking
-The one speed sensor to the right is the John Deere tach. sensor.
-The JD sensor was 600 ohm and gave me a 1.9 ac volt cranking
-Then I lost my starter again.
 

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Found the way to get codes from Cummins ECM
Turn Key on , engine off
press button on field cruise module ( mounted under right side console)
Count the flash of the "Engine Electronic " light left lower corner of right side telltale light group.
Image is of field cruise module. On that tractor it was lose , but it might be normally mounted on a bracket .
Might be able to reach with a long screw driver through range shifter.
 
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