JD 490E Hydraulic System Problem

[Knivens894]

A 490E approaching 7,000 hrs in service was working, but running toward the hot side, when it suddenly lost power and will not spool up under load. Pressure relief valves were removed checked and replaced without any issues being found. The hydraulic tank filters were removed and inspected with no issues being found. Pilot filter was removed and replaced, again with no issues being found. The pilot pump was pressure tested and found to meet specifications. Pressure testing the main pump revealed 3,850 PSI (out of specifications). The angle sensor setting was checked and is out of specification, unable to meet the voltage using the slots provided for the bolts. A new angle sensor was installed, but again, was not adjustable to specifications using the bolt slots in the angle sensor. Does this mean it has had a main pump internal failure, or could there be some other issue(s) that need to be checked first?

 

[wilko]

Do a search on Hitachi 120 problem, same machine and prone to electronics problems. Sorry, but it's a tough problem and answers are elusive.

 

[Knivens894]

Thanks Wilco! I have been talking to the hydraulics shop and we have narrowed it down to no signals to the pump control solenoids. They advised of a similar problem on a Hitachi 120 which had slipped into a pond. I believe they are correct because my operator put this machine into a pond two days earlier and it had to be towed out. Apparently the harness solenoid signal legs break continuity when it is put under water. I have opened the harness at the pump end, and while the wires were dirty and greasy, there is no sign of wire insulation breakdown. I plan to ring out the solenoid wires from the CPU, and if any are found open or shorted, replace them. The CPU is still throwing error code, so I believe it is still operational.

 

[wilko]

Electrical gremlins on these machines are so common it's mind boggling. Lots of problems, few solutions. One fellow on here (Spitzair) cured his with a new wiring harness, pretty sure that's what mine needs too. A dip in the pond would bring out the worst in a sketchy harness. A leaky exhaust is another driver of bad harnesses.

Hope you figure it out without having to throw parts at it. Please keep us apprised on what you figure out.

I see there's another new thread just started about 120-2 gremlins. His is too fast and kills the engine. Mine alternates between too fast and too slow, with just enough just right to keep me from setting it on fire.

 

[Knivens894]

Wilco, I checked into buying a new harness and none are available from the dealer. A used harness is available, but for all that work, there is no assurance it will be any better. After opening the pump harness to reveal the wires, all my wire insulation is in good condition.

There is a main connector for the hydraulic system wiring just behind the back of the seat. It is shown on the wiring diagram for the machine in the service manual. Taking the clue that water caused it, I took the plate out supporting the front of the computers to uncover it. It is covered with mud and has obviously been under water. The attaching cover for the connector was also askew. Before I mess with it, I sharpened the probes on my multi meter and plan to check conductivity of the conductors per wire color code to the solenoids to see if that connector is the problem. I highly suspect that connector is the cause of my problems, and since your problems are intermittent, I would suspect yours too. I have no signal to the solenoids and can not get the angle sensor set using the mounting bolt slots. Both signals go through that common connector, and it is the only break point in the wiring harness.

I would recommend you open yours too. I plan to clean it thoroughly with electronics cleaner and carefully inspect the connectors there to eliminate moisture and any corrosion. I will let you know what I find.

 

[Delmer]

... I plan to clean it thoroughly with electronics cleaner and carefully inspect the connectors there to eliminate moisture and any corrosion...

If it's covered with mud, you're not going to hurt anything rinsing it off with a garden hose. That's what I'd do to anything that's been flooded in dirty water, cell phone, ECM, starter, whatever.

 

[Knivens894]

Thanks Delmer; I used three cans of electronics cleaner on it, it was full of dirt, and was not easy to clean. Those connectors make contact on a very small portion of the pins, and with low voltage signals, I.E. 4.40 on the angle sensor, any small amount of debris can be an interference. There were so many wires in and out, I gave up on checking it before cleaning the connector. Also for anyone else trying it, put the exterior plastic covers back on before reattaching the connectors and pay attention to the red torque indicator pins. I will see tomorrow if the cleaning resulted in success. I have to get the harness redressed in the pump area that I previously opened tomorrow before testing it. It is certainly true the whole area behind the seat needs to be cleaned with a hose. The connector in question is attached to the back lower support of the seat structure and there is much back there that needs to be cleaned out. When the operator put it in the pond, it put mud and water everywhere. Water and mud did not get up to the seat, but in trying to dig himself out, it covered the floor board and the subject connector behind the seat at the floor board level.

If it works correctly tomorrow, I will hit it with a hose to get the rest of the dirt and debris out. It is even on the inside of the rear window. Finding the connectivity problem to get the machine working again is my primary goal at present.

 

[Knivens894]

GREAT NEWS!!! After thoroughly cleaning the open connector mounted on the lower back seat rail and reconnecting everything, the machine is now back in normal operating order. I highly suspect many of the harness issues reported on this site in machines of this type are caused by this connector in the hydraulic's system wiring harness. Others have blamed failure within the harness, but in my case it was simply a dirty connector, and the connector was one I did not know existed until I researched the manuals.

As for Delmer's comment, as an electronics apprentice many years ago, I was taught to never use water in cleaning anything electronic. Water promotes corrosion and these pins have a very small contact area and some signals are very small in this system. We always used canned electronics cleaner or alcohol. Water is fine for open spaces, but not on sensitive electronics contacts where even the smallest amount of corrosion can and does cause major problems. Using the correct cleaner for the job is much cheaper than having to fix future problems caused by using alternatives.

 

[Delmer]

If it's covered with mud...

Don't be afraid of the dihydrogen peroxide. universal solvent and all. The mud caused your issues, get rid of it however you like, I'll stick to water.

 

[Knivens894]

My problem is back, much to my dismay. After a long search I find the ground circuit to the PVC has been lost. There is no ground source to the pins at the connector to the PVC, so therefor the PVC cannot signal the solenoids for control, leaving the swash at minimum. Does anyone know the location of the source for the grounds to the PVC on this unit? I have the pin numbers at the PVC connector, but no idea where to look for the connection to ground source without opening the harness and tracing back the wires.