4720 PTO issue??? Help!!!

[bill boyce]

I recently bought a 2008 4720 cab with 900 hours. I am having a recurring problem with the pto. It came with a mid mount mower. Every time I mow with either the mid mount 6' mower or my 7' brush hog, after about 20 mins of mowing and I disengage the mower (pushing the yellow switch), the pto will not turn on again. The lights on the dash will light up either with the 540 or 2000(mid mount) but neither pto will not engage. Once the hydraulic fluid cools down(usually overnight) the pto will work fine until I turn off pto then I have to let it sit for a long time then it works again. I replaced the pto switch even though it wasn't bad and I just replaced the pto solenoid and armature. I have looked all online and talked to the head shop manager at my local dealer and a couple of other dealer mechanics, they haven't heard of this happening and they don't know what it could be. I am so frustrated with this. I can't afford to take it to the dealer. Any help or ideas would be great, if anyone has heard of this on other tractors please let me know. :banghead:

 

[joecdeere]

I have a PDF of the technical manual you're welcome to. Shoot me your email if wanted

Joe

 

[Silvic]

Never heard of this.
Since you state that the failure condition changes as the fluid cools down, it sounds as if it might be hydraulic fluid related from your description.
When was the last time the fluid was replaced, the filters changed, etc?
There is if I remember correctly one inline filter (two if you have power beyond) and the one big main filter.
When it happens have you checked the hydraulic fluid level. If contaminated you could have foaming.
What is the condition of the fluid, hopeful not milky?
Have you ever had the pto shut off after an extended use like an hour or two of use or does this only happen after disengagement and the reengage attempt?
With it being a 4720 it is e-hydro. How is the steering and drive-ability after it happens any jerkiness or slipping in any high low medium position.

 

[bill boyce]

When I bought tractor I was told all filters had just been replaced. I may do that next and see (just taking the word of the owner). Yes manual calls for cleaning the suction tube, inline filter and replacing the large filter.
Fluid is clean, the first time the pto stopped working I checked fluid level and it was low, I added fluid but still didn't engage pto. Yes I have had pto shut off after about 1.5 hour of use that is the longest I have been able to mow at one time. Yes it is e-hydro, everything else on tractor works great and has plenty of power. It has a loader and it works great too.

 

[bill boyce]

I sent it in a PM.

 

[Silvic]

Just went to the manual and looked up some stuff.

Do you have a service manual?

Page 621 states under trouble shooting:
Problem
3. PTO does not operate ..................................... a. PTO valve faulty

Have you done a test on the valve? Page 624 PTO valve pressure test

If you don't have a manual PM me your email and I can send the applicable pages. The whole document is way to big but it will show you how to do the test.

Oh I see you have another offer for the manual It is large. 127 MB

 

[bill boyce]

I have not done a valve test. I'll pm you.

 

[bill boyce]

I just looked up pick of valve. I replaced the solenoid and armature on the valve. Yes please send me info on how to do valve test. I just mowed with tractor using the belly mower mowed great for about 30 min, turned it off to back up, would not work again. Guess I'll finish mowing in the morning.

 

[joecdeere]

Bill, manual download link should be in your email

 

[waycoolmarine]

the ptos engage with electric coils ,my guess would be theres metal floating around in oil and attaches to magnets , when you turn off the are still holding metal and will not grab pto try checking the screen in hydro oil , if you have a bunch of shavings don't freak out it will be ok , ive seen more than a couple tractors with lots of shavings , that's why theres a screen

 

[Brown Dog]

Did you check your seat switch ?
I bypassed mine on all 3 tractor lol

 

[Brown Dog]

Does tractor have E-PTO option ?

If so, does this happen in either setting ?

 

[bill boyce]

Update: I talked with previous owner and he suggested that I replace hydraulic fluid and filter. I thought he did this before I bought it in Dec. So I just replaced fluid and filter. I cleaned both transmission screens neither were dirty. Fluid was dark almost black in color. Put new filter and fluid in. Still did the same thing after mowing for about 10 min. This is so frustrating!!!!! I think I will bypass the seat switch. If that doesn't work only thing left to do is to tackle pto pump. I don't think it has the e-pto option.

 

[bill boyce]

There were a few metal shavings in the transmission screen but none in the inline screen. Overall both screens were very clean to me. Any ideas on fix with metal floating around? Only thing I see is to take off the pto pump and see whats in it.

 

[Spanner]

I believe Joe has supplied you a copy of the manual. Have you read it yet?

Why bypass the seat switch? What diagnostic procedure has led you to this decision?

The dark fluid is perhaps a clue.

Minor shavings in the screen are not abnormal.

 

[bill boyce]

Yes I have read both the owners manual and the tech manual. There is nothing in there that specifically states my problem. I am just trying to narrow down why it is doing this. The dark fluid tells me it was time for new fluid.

 

[Spanner]

So you need to diagnose the problem when it is faulting. That is, when your tractor has been working and the PTO won't re-engage.

Under those conditions you need to verify power to the PTO solenoid. A simple procedure with a circuit tester probe/lamp.

When the fault occurs place someone in the seat to operate the PTO switch on-command for you.

Disconnect the PTO Solenoid at the weather-pak connector. Insert probes into both terminals of the power cable connector and operate the PTO switch. (Soldier B's job). Your tester should light-up. Or your VOM should show voltage present.

Work forwards or backwards from there.

Read the test for the PTO switch which requires accessing the rear of the switch etc.

I agree - Dark oil is ominous.

:wrench:

 

[Spanner]

You will be testing the connector to the two wires coming off the solenoid (Item 16) shown:


Just asking: How comfortable are you with Electrical & Hydraulic work?

The dark oil could indicate 'overheated' hydraulics or just very old oil. You did say the oil was supposedly changed prior to purchase?

Refilling with JD Hygard is recommended.

On the overheating concept - I wonder if components in the PTO valve are 'dirty' now, or sticking when heated, thus preventing the valve from operating correctly?

 

[bill boyce]

I will try to do the test. I have already replaced both the solenoid and armature with new ones. I tested old components and they had proper ohms. I am pretty sure looking at that oil it was not changed anytime soon nor the filter. I agree with the possibility of the PTO valve dirty or sticking when heated.

 

[Spanner]

Replacing the Solenoid and the Coil (Armature) may not have been necessary. That's why you need to prove the power supply to the connector first.

Edit to add: If the power is present at the connector when the machine is at the hot operating temperature needed for previous fails, and you have a new coil and solenoid then you go forward into the valve block I think.

Keen to hear your progress Bill.

:wrench: