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Kevin, Technician
Category: Agriculture and Farm Equipment
Satisfied Customers: 722
Experience:  Over ten years of expirence in Ag Electronics and Hydraulics
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This Question is . I'm having some problems with a 4710

Customer Question

This Question is for KEVIN. I'm having some problems with a 4710 John Deere Sprayer.
Submitted: 4 months ago.
Category: Agriculture and Farm Equipment
Expert:  Kevin replied 4 months ago.
Hello, and thank you for the request.What kind of problems are you having with the sprayer?Let me know when you have time.Thanks,
Customer: replied 4 months ago.
Hey. If the sprayer is in Park the psi are good but once i drive the psi drops and it does'nt spray the correct rate per acre, but sometimes it does spray the correct rate. All of a sudden it works fine for a while and then again the psi drops while driving but once i stop they go up again. I've checked the filters and their clean.
Expert:  Kevin replied 4 months ago.
When the problem occurs does it come and go instantly or come on slowly? Also how many gallons per acre are you spraying and what is the approximate PSI when everything is working correctly?Thanks,
Customer: replied 4 months ago.
17 gallons per acre, 60 psi, 8mph Thats when it works correctly, the problem occurs instantly the PSI just go's down. If i then turn the pump off an on or recalibrate the pump then sometimes it'll pressure up again. But the pump cannot make more than 60 psi now and before it could go up to 120PSI
Expert:  Kevin replied 4 months ago.
Ok so the problem is most likely a hydraulic issue. The sprayer has a load sensing closed center hydraulic system. It is possible that the hydraulic pump isn't getting enough signal to go into stroke. To test for this problem set your spray off pressure at 150 psi and raise the boom to full up and hold the button. The boom function will command full stall pressure from the hydraulic pump. If The solution pressure goes up to 120 and then drops off when the boom raise button is released then it is load sensing issue. Also note if any other hydraulic functions seem weak or sluggish when the fault is active.Keep me posted,
Customer: replied 4 months ago.
I now did the test as you recommended and the pressure only go's up to 100 PSI and if raise the Boom to full up and hold the boom up button and then release it the PSI doesn't go higher then 100 PSI or lower if i release the button. The PSI just stay at 100 what's the next step or what would you recommend?
Expert:  Kevin replied 4 months ago.
The pressure is a bit low but that can be due to normal wear in the solution pump.We have actually started adding a manual pressure gauge from the pump outlet that is visible outside the rear window. The added gauge helps diagnose solution issues. If the pump pressure is high and the boom pressure low we know there is a restriction between the pump and the boom. I have seen the hose going to the boom develop an internal blister that can slowly restrict flow to the boom.Just to confirm, have you pulled that goofy inlet strainer in the pipe at the pump inlet?Unless the fault wasn't active during our hydraulic test we can rule out a hydraulic load sense issue. This leaves us with a solution flow problem.Are you using water as your carrier?Thanks,
Customer: replied 4 months ago.
I now checked the hoses for flow restrictions and they look fine, the restrainer at the pump inlet is also fine.
I'm using water as the carrier. As far as i could see the fault was not active during the test.
What would you recommend to do next?
Customer: replied 3 months ago.
Hey is there something else we should check out or what do you recommend?
Expert:  Kevin replied 3 months ago.

Sorry about that I missed your first reply. You are my only open question this month as I've been working too many hours to work with Just Answer as of late.

So if we know the suction circuit is clean and the pressure hose is in decent shape we are left with only a handful of possible causes. I have seen small leaks in the suction circuit allow the pump to pull air but it would only occur when the tank is under 200 gallons. In addition you should notice a small external leak. I'm doubtful that a suction leak is the cause of your issue.

The next possible cause is the hydraulic fault I mentioned previously. In order to narrow down this fault you would need to wait till the fault was occurring and then stall a hydraulic boom function and see if the pressure came back up. This is a still a likely cause for the fault and would be easy to rule out by performing the test when the fault is occurring.

If the pump won't reach stall pressure when the fault is active we can rule out the flow meter, pressure sensor, and radar. This leaves us with the solution pump control circuit. If the solenoid control valve that is responsible for controlling the solution pump speed sticks it would prevent the pressure from being acquired. Often you can hear the solution pump when it is wound all the way up at stall pressure. If you can't hear it when the fault is occurring then that means the valve isn't opening full up allowing the pump to spool up. If you do hear it then we need to go back to the solution system. My guess is that the pump isn't spooling up which would suggest that either the load sense circuit isn't working or the control solenoid spool is sticking.

Let me know what you are seeing and I will try to keep an eye out for your response.



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