John Deere 4720 running rough

Dci · Jan 2, 2019

Happy New year to all.

Update.

I have replaced the complete priming pump system,new lift pump,New air filters,tried running the tractor with fuel cap off,and removed the fuel tank completely and flushed it out with gas. Reinstalled the tank new fuel and started it up and the problem still exist. &#55357;&#56865;

The one thing I forgot about right before this all started was I was boxblading and the engine just shut off and the oil light was flashing. I checked all liquid levels and everything was correct. It repeated this 2 more times within 30-45 min then the rough running started when under a load.

When I shut the tractor off it thru a error code of 74. (Display mode switch stuck on). The code or the shut down of the engine has not happened again.

I’m not sure of the next step.

Thanks for all the post..

thepumpguysc · Jan 2, 2019

Yes they ARE DIFFERENT.. A shop manual IS REQUIRED..
I dove into my 1st one w/o it.. bent 1/2 the push rods..lol
Theres really only 2-3 things an "owner" can do w/o a manual.. check for air, replace the supply pump & check/replace the shut-off solenoid..
& maybe the fuel regulator..?? EVERYTHING ELSE is done under the v. cover..

radios1 · Jan 2, 2019

I was thinking, since it has a turbocharger, maybe THAT is the problem. the engine can't run properly without that working correctly, especially at the higher RPMs and loads..

ruffdog · Jan 2, 2019

radios1 said:
I was thinking, since it has a turbocharger, maybe THAT is the problem. the engine can't run properly without that working correctly, especially at the higher RPMs and loads..

....or, if the waste gate isn't operating right by always changing pressure from the turbo.....hmmm?

Dci · Jan 4, 2019

ruffdog said:
....or, if the waste gate isn't operating right by always changing pressure from the turbo.....hmmm?

Is there a way to check the turbo?

ruffdog · Jan 4, 2019

I would assume that there would be a gauge port for checking boost pressure.

arlen4720 · Jan 6, 2019

There would probably be signs of over fueling if the turbo was not supplying enough air

radios1 · Jan 6, 2019

arlen4720 said:
There would probably be signs of over fueling if the turbo was not supplying enough air

not in a computerized fuel injection system that should compensate for the fuel mixture if it has the correct and accurate inputs.. if those inputs are off, anything goes!.. not enough air could mean not enough fuel to compensate!..

arlen4720 · Jan 7, 2019

radios1 said:
not in a computerized fuel injection system that should compensate for the fuel mixture if it has the correct and accurate inputs.. if those inputs are off, anything goes!.. not enough air could mean not enough fuel to compensate!..

I don’t think it works like that. It just dumps in fuel and the turbo takes care of itself. There are no “inputs” that look at mixture

radios1 · Jan 7, 2019

arlen4720 said:
I don’t think it works like that. It just dumps in fuel and the turbo takes care of itself. There are no “inputs” that look at mixture

but it does.. not the turbo, but the fuel injection system works that way, I already posted the link here that shows this.. ok, here it is.. Common Rail Injection System Pressure Control