Question on JD490E PVC code reading

[Knivens894]

The JD 1504 technical manual says without a jumper in the computer code reader connector there should be a steady one second on and one second off PVC LED output. It also says if no fault code exists or trouble is beyond the scope of the self diagnostic function, with the jumper installed, there will be no flashing of the LED. My PVC flashes a steady one second code with or without the jumper installed. Does this mean the PVC has failed? The input of someone with knowledgeable experience in such a situation would be appreciated

 

[Knivens894]

Had a tech with 30 years experience come out to diagnose my machine's problem of low speeds in all motions. He first found a spring broken in one of the relatively new pump control solenoid valves. Electrically it was good and in spec, but it had failed mechanically internally. Correcting that allowed 3,800 PSI out put from the main hydraulic pump versus 2,000 PSI before, but was still well below specs.

Further investigations and testing showed the output of the engine injector pump was inadequate to develop full power. He says he has seen that one a number of times and in his opinion it is caused by dirty fuel causing excessive wear internally to the pump. I had been looking for issues in the hydraulic system and the PVC system for some time. I ask him how he knew to open the solenoids to inspect them internally. He said "experience" based upon all functions slow and low pump pressure output. When the defective solenoid was replaced, the PVC computer system tested as having no faults. The machine would not develop specified main hydraulic pump pressure, and again, based upon experience, he pressure tested the injector pump output to determine it was producing only 1/6 the specified pressure for proper operation and full power delivery from the engine. It was cranking easily, running smoothly and spooling up on command. I had never suspected the problem was engine related.

My fuel supplier has a filter in the piping that fills my tank. I have a filter on the fuel tank used to refuel the machine complete with water separator. I regularly change the engine mounted fuel filters with those supplied by JD. The machine has 6,500 hours, so perhaps the injector pump just wore out internally due to use, but I defer to the Tech's opinion because he obviously knows more about this machine than I do.

This was an expensive experience. I had replaced the computer's sensors, replaced the PVC computer, removed the main hydraulic pump and took it to a pump shop to be be torn down and inspected. We spent many hours looking for electrical faults I could never find. All relief valves and control valves were removed and inspected (except the pump control solenoids which I knew to be recently new). It took 6 weeks to get the Tech here from the time of my request. I spent many hours looking for phantom faults, defective wiring or defective connections. Meanwhile the machine was parked and unusable now approaching the third month.

 

[joeblow]

It could be a main relief problem.There is the main relief valve on top that gets contaminated and does not seat properly.There is a surge relief on the under side of the valve body that is set at a higher pressure and will act as a main relief .Try bottoming out the main relief on the top of the valve and see if your situation improves.

 

[Knivens894]

Joe;

We have removed and inspected those regulating valves and have them currently set to full in. The result of all the work to date has been a max system pressure of 3,800, well below the full power requirement. The overhaul of the injector pump increased the speed at which the machine will move, but it does not have normal power. The Tech reported last time the PVC and its sensors are all normal.

I have requested the tech return for further evaluation, and again their shop put me on their waiting list. Last call took 6 weeks to get a response. Indications are they next intend to do a pump flow test upon their return. The main pump was recently removed and taken to an overhaul shop for tear down inspection. They found nothing of concern internal to the pump. The shop's opinion is the system has a bypass relieving the pressure even at full output somewhere. I ask them to do a pump flow test while it was there for inspection, but they refused fearing it could contaminate their test system. Their shop policy is to only flow test newly overhauled units. Finding the bypass source is beyond my capabilities and renders the machine unusable which is a real bummer.

 

[joeblow]

does the hydraulic oil get hotter than normal? That will tell you if it is bypassing.There are unfortunately a lot of possible causes for your problem.Did the hydraulic shop reset your pump angle sensor? Did the tech that came out check the voltage at the differential pressure sensor?When you removed the main relief did you inspect it for contamination?That machine series (dash 3) was hitachi s first stab at computerization and made for a steep learning curve for us techs.Have the dealer check John Deere s Detac system for more possible causes.That is what you pay the big money for! They can be a money pit for the poor customer who relies on a tech that does not have a complete understanding of that system.

 

[tool_king]

The JD 1504 technical manual says without a jumper in the computer code reader connector there should be a steady one second on and one second off PVC LED output. It also says if no fault code exists or trouble is beyond the scope of the self diagnostic function, with the jumper installed, there will be no flashing of the LED. My PVC flashes a steady one second code with or without the jumper installed. Does this mean the PVC has failed? The input of someone with knowledgeable experience in such a situation would be appreciated

Knivens
shoot me a email at tool_king@hotmail.com .Thave some inifo on the 490e that might be helpful

 

[Knivens894]

Joe;

Thanks for the interest and the reply. The hydraulic oil is running hotter than normal. Temperature rises very quickly to near red line and stays there. The new angle sensor was set by the Tech and was checked by us at 4.40V. The DP sensor was replaced with a new one. It was found set at 1.14V, was replaced with a new sensor set at 0.5 V per manual. The PVC was replaced with a new one and no change, so it was removed. The new DP was removed and replaced with the old as originally set, again no change. The Tech's computer check says no problem exists in the control system or its sensors. That is when he moved on to checking the engine and determined the fuel injection pump needed overhaul. We sent the injector pump out for overhaul and reinstalled it with little resulting benefit.

Talked back with Hydraulic shop on the main hydraulic pump. They say there was no sign of any problem with the pump internally. Upon checking again, my in house mechanic says he did not remove and inspect the lower by pass valve, just the upper one, so that is on his list for first thing tomorrow when he returns. The hydraulic shop's opinion is the system has an internal by-pass, preventing proper op pressure development.

I believe we have an internal by-pass going on somewhere in the system, but the problem is how do we find it? Any suggestions as to how to find it would be appreciated.

 

[Knivens894]

To Joe and Tool King;

Your advice was spot on. The relief valves were the problem. I overhauled them and replaced the surge valve which fell apart upon removal. The o-rings did not look bad but were rather square. No cracks or debris. The new o-rings fixed the problem. I readjusted the pressures per the manual and all is well with performance now. Apparently with age these o-rings go south. Anyone with a low hydraulic pressure problem should just overhaul the surge and relief valves before going into anything else. I spent 4 months chasing this issue and more than 10 K in money. They valve overhauls were less than $40. Had I only known where to look. Joe and Tool King know what they are talking about. Thanks to them and this forum!

 

[tool_king]

Kirk
You are very welcome. Glad I could help to get you back up and running .

 

[Knivens894]

In the continuing saga of my 490E, resealing the main pressure regulating valve and replacing the surge relief allowed me the return to specified operating pressures in the main hydraulic system, but I am now having problems with machine over heating during operations. Temperature goes up to near red line and I know the hydraulic system is hot because steam comes off the bucket cylinder while digging in water. I have read other posts suggesting the o rings in all the control solenoids go south over time. This machine is approaching 8,000 hours. How should I find the pressure bypass and fix it? Would the heat source be identifiable with a temperature gun? Any experiences and guidance in going after this problem would be appreciated.