John Deere 4720 running rough

[thepumpguysc]

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]

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]

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

 

[thepumpguysc]

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]

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]

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]

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]

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]

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]

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