John Deere 4720 running rough

[Dci]

Hello all,

I have a JD 4720 that has approx. 1100hrs. It has just started running rough when the engine gets a load on it. It acts like it is getting air in the fuel to me. My best description.

I have drained the fuel tank,replaced the fuel filter, and replaced the fuel filter housing/priming pump.

The tractor does not smoke at all during any of the running conditions. You can drive the tractor and it will mostly run fine then lower the box blade and as soon as The governor kicks in it starts running rough. Then you can let off the hydrostatic direction pedal and it will immediately straighten out...

Any ideas on my next step?

Thanks in advance for your time.

Dewayne

 

[thepumpguysc]

Lift/supply pump, not supplying enough fuel to power the load.

 

[Zebrafive]

My first thought was bad fuel, second fuel filter, but looks like you covered those things. Dirty air filter? Final thought is dirty injectors?

 

[kthompson]

Reading the "thepumpguysc" suggestion and what he does would suggest you check that. Hard to beat a pro at his job.

My thoughts you have already covered except the air filter and you are checking it. Had such issue on my JD once and was not getting solid seal with fuel filter gasket.

 

[Dci]

Lift/supply pump, not supplying enough fuel to power the load.

First thank you for your time. Second I知 not 100% sure what pump you are talking about? Would this be the pump right after the tank just before the fuel filter?

 

[ruffdog]

Do you use any Biodiesel that you know of? Is it cold there?

 

[Dci]

Do you use any Biodiesel that you know of? Is it cold there?

Not that I am aware off. The air filter is New as well. I知 in Florida. Thanks

 

[radios1]

Not that I am aware off. The air filter is New as well. I知 in Florida. Thanks

you live in Florida, but, it can still drop to 20F. in the winter there, I personally experienced that, so, how cold was it when this happens?..

 

[thepumpguysc]

Yes, small pump after the tank & before filter

 

[Dci]

Yes, small pump after the tank & before filter

I replaced the small pump and unfortunately no fix..It was 78* today...so fuel is not ice Ing

 

[K5lwq]

Not familiar with the 4720 but I think it is starving for fuel.

A couple of thoughts.

1. Is the filling cap vented? Try running it with the cap loose to see if it improves.

2. Is there a screen inside the tank on the fuel line that could be clogged?

3. Could there be trash in the tank that is restricting the suction line?

 

[radios1]

replace any rubber fuel lines, they can get cracks or pinholes that you can't notice. lastly, your injection pump may need to be serviced..

 

[Crankygranke]

I have the same problem with my 4520 compact tractor. 2004. 1800 hours. I've done filters, air and fuel, cleaned tank and screen, fresh fuel, replaced fuel lines also the transfer or lift pump. I located a check valve in the return line and just got it. I will post if it fixes the problem.

 

[arlen4720]

I replaced the small pump and unfortunately no fix..It was 78* today...so fuel is not ice Ing

You mentioned the hand priming pump before, but did you replace the small lift pump that is mechanically driven from the side of the motor? It sounds like it is most definitely a fuel issue. Does the turbo seem to spool up normally under load?

 

[Crankygranke]

You mentioned the hand priming pump before, but did you replace the small lift pump that is mechanically driven from the side of the motor? It sounds like it is most definitely a fuel issue. Does the turbo seem to spool up normally under load?

Yes i did. It made no difference at all. Nothing I've done has made any difference. Hopefully i will be able to change the fuel check valve. I've been to 2 dealers and they haven't been able to help without me taking it to them.

 

[thepumpguysc]

Cranky>> the return check valve, was it on the top cover of the inj. pump.??
The problem "I'm" having helping is>> JD put several diff. inj. systems on the 4720 AND the 4520.!!
1 was a Stanadyne/RoosaMaster pump & the other is a PFR system where the pump sits in its own hole & is driven by a separate camshaft..
& they get diagnosed differently..
SO.. if the poster can ID the pumps on their machines.. I can probably answer the questions..

 

[kevin37b]

This man knows what he is talking about . Give him correct info . Do not rely on guesses , go with a man that knows his stuff .

 

[radios1]

did you pull the line off after the petcock and check for a good flow of fuel?.

 

[Crankygranke]

yes, it was fine

 

[Crankygranke]

I replaced the transfer pump on the side of the block, it runs off the camshaft. each injector has it's own pump that also runs off the cam it's under the valve cover