John Deere 4720 running rough

thepumpguysc · Dec 30, 2018

OOOHHH.. u have the integrated system.. U BETTER get the book for that thing if u plan on wrenching on it yourself..
Theres some very special instructions..
& the pump & inj. are not cheap.. 1 set{ 1pump & 1inj.} REMAN is OVER 400.00.. it better be something u just cant live with..

Crankygranke · Dec 30, 2018

thepumpguysc said:
OOOHHH.. u have the integrated system.. U BETTER get the book for that thing if u plan on wrenching on it yourself..
Theres some very special instructions..
& the pump & inj. are not cheap.. 1 set{ 1pump & 1inj.} REMAN is OVER 400.00.. it better be something u just cant live with..

I replaced the check valve in the return line and still have the problem. surges about 200 rpm, even if i use the bucket on the loader. I've been running half throttle and low gear to get by. I really don't understand why they used an internal pump system. crazy expensive. does this sound like a pump issue to you? Maybe i could just replace the injectors. It doesn't miss though.

ruffdog · Dec 30, 2018

Maybe not fuel at all.....governor?

thepumpguysc · Dec 31, 2018

Correct Ruffdog.. could be the gov.. I hesitate to offer any advise.. those engines are NOT user friendly without a shop manual..
The owner has done all he can do.. return connector & supply pump..thats it..
Could be a gov problem, could be a stuck/sticking rack on a pump..
Under what conditions did this problem start.. just all of a sudden it started surging.??
Was it low on fuel?? did u immediately change the filters & top off the fuel tank?? Does it settle down w/ a full tank??

Crankygranke · Dec 31, 2018

thepumpguysc said:
Correct Ruffdog.. could be the gov.. I hesitate to offer any advise.. those engines are NOT user friendly without a shop manual..
The owner has done all he can do.. return connector & supply pump..thats it..
Could be a gov problem, could be a stuck/sticking rack on a pump..
Under what conditions did this problem start.. just all of a sudden it started surging.??
Was it low on fuel?? did u immediately change the filters & top off the fuel tank?? Does it settle down w/ a full tank??

It became noticeable during a road run to bush hog. High gear, high rpm. felt just like i was running out of fuel. I had a full tank. I worked that day replaced fuel filter next day. not expecting any more problems. full tank of fuel made no difference. Little to no debris is tank and on fuel screen. When i start it it idles fine, when i increase throttle to say to half it surges a couple hundred rpm for approx. a minute then smooths out. I put it in gear and it surges unless i leave rpm high and low gear. when i take off 1st gear high range accelerate it gets to speed then drops off then back and forth constantly. thanks for the help by the way

ruffdog · Dec 31, 2018

Cranky, Do you know your fuel is good and pure? There have been cases around here that had diesel put in gas tanks, gas put in diesel tanks, all at fuel stations. I would at least swap the fuel before major engine work unless you know it is good fuel.

radios1 · Dec 31, 2018

it could be the pressure control valve or the control unit too.. Common Rail Injection System Pressure Control I'd suggest unplugging the electrical connectors and looking for corrosion on the terminals first..

Crankygranke · Dec 31, 2018

ruffdog said:
Cranky, Do you know your fuel is good and pure? There have been cases around here that had diesel put in gas tanks, gas put in diesel tanks, all at fuel stations. I would at least swap the fuel before major engine work unless you know it is good fuel.

yes i changed fuel when i cleaned the tank and replaced the fuel lines. I also use the same fuel in my other 2 tractors with no problems

Crankygranke · Dec 31, 2018

radios1 said:
it could be the pressure control valve or the control unit too.. Common Rail Injection System Pressure Control I'd suggest unplugging the electrical connectors and looking for corrosion on the terminals first..

I haven't removed the valve cover yet to look there yet. the set up for new pumps and injectors looks pretty tough to do. this set up is way different than anything i've seen. I spent 30 years in general motors dealerships working on cars and trucks.

Crankygranke · Jan 1, 2019

just took off return line to tank to check flow and for air bubbles. good flow and no air in it. any ideas are appreciated

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