JCB JZ140 excavator seems possessed! Help

[guisep3]

Need help.
I start up the machine and it seems like the computer is controlling the throttle of the machine uncontrollably. All filters are new and this problem doesn't have any regularity. Some days it will run full throttle and suddenly it throttle itself down to idle for no reason. Some days it doesn't seem to happen.
Anyone have any clue? I'm in Pittsburgh PA and there's isn't great support locally for these machines. I attached a pic of the serial number of the machine.

Thx

 

[excavator]

Does this machine have any on board diagnostics? Can you monitor voltages and sensors ect. while it is acting up? Years ago i had a Komatsu doing the same thing and it was the alternator regulator was bad. Once it hit 36-37 volts that poor computer didn't know what to do, the throttle would bounce all over the place.

 

[guisep3]

I don't believe there is an on-board diagnostic on the monitor. It's a very basic screen. I will however check the voltage coming off the alternator. I appreciate your input. I have the shop manual and I know there's a diagnostic port but I don't have the software to communicate with the computer.

Does this machine have any on board diagnostics? Can you monitor voltages and sensors ect. while it is acting up? Years ago i had a Komatsu doing the same thing and it was the alternator regulator was bad. Once it hit 36-37 volts that poor computer didn't know what to do, the throttle would bounce all over the place.

 

[guisep3]

Does this machine have any on board diagnostics? Can you monitor voltages and sensors ect. while it is acting up? Years ago i had a Komatsu doing the same thing and it was the alternator regulator was bad. Once it hit 36-37 volts that poor computer didn't know what to do, the throttle would bounce all over the place.

Measure the voltage coming off the alternator, it was about 28.4 volts. Wondering if this alternator has a built in regulator.
I would think if the ecu was bad the machine wouldn't run fine most of the time.
Do you think it could be the throttle regulator solenoid. In the past I had the fuel shut off solenoid go bad and replaced.
Is there a way to test the solenoids? Is there a resistance they should show?

 

[skata]

On other jcb machines, you press and hold the i or info button for 30 seconds to get codes and service resets.
Does this have auto idle?

 

[guisep3]

On other jcb machines, you press and hold the i or info button for 30 seconds to get codes and service resets.
Does this have auto idle?

Yes the machine does have an auto idle button. I will try to press and hold the auto ideal button to view a code.

 

[anuradha]

Hi,

If you have the shop manual then find out the controller voltage in put & out put section.

There you can find the voltage in puts of speed dial switch to the controller and voltage out puts to throttle control motor from the controller.

If you can, Check these values whether correct voltage levels are there. Some times you might have to pierce few wires to measure the voltages. If you can use an oscilloscope for this, then you can see voltage signals wave form also & it will be very useful.

This kind of problem has happen to me as well. My issue was the bad controller. From above informations it seems this case also might be a controller issue but to determine that correctly you should check the relevent wiring lines as well, before checking the voltage signals at the controller.