Hello all, does anyone know about the swing and dig sensor layout on a John Deere 120C? Got two now that run rough (difference customers) ever now and then like the ecm is telling the pump to advance timing to keep up with the load of the machine working but it will just be running not moving. You can load the machine by swinging or digging and it will run perfect until you stop moving. You can kill them and start right back up and they’ll run normal sometimes. Usually takes a few key cycles. 120cx034408 is the serial number for one of them.
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John Deere 120C timing advance
- Thread starter kmorris
- Start date
mg2361
Senior Member
Welcome to HEF kmorris
!
Do you mean the engine is intermittently running rough? Run rough all the time or does it run rough at a specific rpm?
If it is intermittent I would be looking real hard at the wiring that goes from the DE10 injection pump back to the ECU for bad connections or wiring. Don't check voltages at the pump solenoid, it is PWM solenoid so it would not be an accurate way to diagnose.
Otherwise you would need Deere' Service Advisor to watch some particular readings to diagnose.
The dig and swing sensors will not affect engine timing. Engine timing is controlled by the ECU and is dependent on rpm's, load, engine coolant temp, ambient air temp, fuel temp, just to name a few.
!Do you mean the engine is intermittently running rough? Run rough all the time or does it run rough at a specific rpm?
If it is intermittent I would be looking real hard at the wiring that goes from the DE10 injection pump back to the ECU for bad connections or wiring. Don't check voltages at the pump solenoid, it is PWM solenoid so it would not be an accurate way to diagnose.
Otherwise you would need Deere' Service Advisor to watch some particular readings to diagnose.
The dig and swing sensors will not affect engine timing. Engine timing is controlled by the ECU and is dependent on rpm's, load, engine coolant temp, ambient air temp, fuel temp, just to name a few.
One of them has a new wiring harness installed by a deer tech. I checked it when I first started working on it. It was also having fuel derate codes due to excessive return pressure. The lift pump had failed and low fuel pressure killed the injection pump. I replaced the worn fuel system Components, all rubber lines gaskets and seals popped the injectors and replaced the injection pump. It ran perfect other than it doing its usual every now and then running rough issue according to the operator. The couple times I’ve seen it, you can start it up at idle and it will sound slightly different and as you raise the rpms it gets worse. Reminds me of a common rail system that is running at max rail pressure at idle but this isn’t a common rail. Just a real high pitched almost popping rough sound. You can kill it and it will usually run normal. I have the Texa diesel laptop and have monitored parameters with nothing out of the ordinary. The reason I bring up swing sensors is once you start to move or load up the machine it runs smooth but as soon as you stop it starts running rough. Also note that it has never went from running normal to running rough while being operated or the other way around. Only after you have cycled the key hot cold doesn’t matter.
mg2361
Senior Member
Let's just deal with one machine. Let's start with the one with all the new parts (injection pump/injectors, lift pump, wiring harness, etc).
What active and stored codes do you currently have for both the engine and the machine?
Has the ground near the ECU been thoroughly checked/cleaned (a known issue with 120's with rough running issues)? Was the short harness between the ECU and the engine harness also replaced? If not I would be checking that harness real close as well.
While at the ECU, remove the cover over the ECU and press with your finger or a hammer handle on the side of the ECU while the engine is running to see if the sound of the engine changes. Also what part number is on the ECU?
When you monitored readings, did you compare the following while running well vs. running rough? Were they the same or different?
Closure Error
Decay Time
Rise Time
Shutoff Adjustment
Valve Closing Time 0-3 for 4 cylinder
Engine Load
Fuel Mode
What active and stored codes do you currently have for both the engine and the machine?
Has the ground near the ECU been thoroughly checked/cleaned (a known issue with 120's with rough running issues)? Was the short harness between the ECU and the engine harness also replaced? If not I would be checking that harness real close as well.
While at the ECU, remove the cover over the ECU and press with your finger or a hammer handle on the side of the ECU while the engine is running to see if the sound of the engine changes. Also what part number is on the ECU?
When you monitored readings, did you compare the following while running well vs. running rough? Were they the same or different?
Closure Error
Decay Time
Rise Time
Shutoff Adjustment
Valve Closing Time 0-3 for 4 cylinder
Engine Load
Fuel Mode
Substratum Ex
New Member
Was just wondering if this ever got solved? My 120C does the same thing, jiggled some wires and plugs in the door behind the cab and hasn't messed up since