I have a JD 490e. It was working fine. I stoped for lunch, came back all functions were slow. Checked oil and changed filters. When I work the functions the pump doesn't seem to kick in. If I close the bucket all the way and hold it against the thumb you can hear the pump kick in and functions work at correct speed. Two years ago the dealer put a new main pump and went through the load sense valve. When the machine sits over night it'll work for 5 or 10 mins then acts up with the slow function problem... Almost like when it gets warmed up it starts acting up.
That machine has a differential pressure sensor and a pump angle sensor and 2 solenoids to shift pump to high displacement. Sounds like one of them was having a problem.
Ok, I know where the angle sensor is and believe I can check it with a volt meter. Where is the differential pressure sensor and is there a way I can check out. And which solenoid should I check? Thank you
The DP sensor should be on the front side of the valve bank with a boot covering it strapped with a zip tie. If you back probe the connector the voltage drop with key on should be around 4 volts plus or minus 2 volts. Also the connectors for the pump solenoids become disconnected and I have seen the wires damaged.
How do I check the solenoids?
So I checked the dp switch and I'm getting a little over 5vdc in and about 4.7 out which is to high I believe.. I also checked the angle sensor and can't seem to adjust it to 4.4 without completely removing the screws and moving it way past where it should stop.. any ideas?
You first have to make sure the thing is at full swash.Disconnect the two pump solenoids and wait 5 minutes with machine at an idle.Put a pressure gauge on the pump and check the main relief.Those things have been a reoccurring problem because they pick up every piece of crap in the system.Best to screw it right in and use the surge relief on the bottom side of the valve bank.
Sorry, I've been working late days. I have a jumper harness I use for the dp and angle sensor. The dp sensor sounds ok if it was measured with key on engine off. I agree disconnect solenoids (mark them first) run at idle, then measure, you must have a service manual if you are aware of 4.4. You should be able to take a resistance reading on each solenoid. Some times I switch them to see if they are working. Also look at thread for 790e as it is similar system.
Actually it is 4.5 vdc.I will have to look through my notes but there was a few other things you could do to tune those things up.If you have access to deeres Dtac system then there are several files on the 490e and 790e system.I worked for a Deere dealership for 22 years and had my share of problems with those old machines.As they are now going on 30 years old the wiring is probably a little crispy. I would start there because when the temp increases so does the resistance.Check the harness and connections.It is tedious I know but it may help rule out more expensive problems.
So I had to open my big mouth, as soon as I answered this post one of my customers machines went down with this same malfunction. In my case the a sensor was out of range as you are talking. Buy a new a sensor and get it adjusted in range. The big question is deere/hitachi sensor or aftermarket? The hitachi manual lists voltage of 4.4v plus or minus .05, set with engine running pdsv sensors disconnected. Solenoids should be 18 ohms They got rid of the main relief on top after sn 024999, and just ran the bottom relief. My question is with no surge relief, and only a main relief, turned all the way in what would prevent system pressure from getting over 2500psi for entire system any function?
Try taking the relief valve out and blow it out.If there is any contamination you may have a bad cylinder packing.Also check the pilot pressure.
Thought the same, went to machine with new relief in hand, with new relief turned all in will only pull 2500psi, thought surge relief but doesn't have one in this -3 machine, pilot pressure at pump in spec, I can hear a relief kicking off, but can't locate. I should add this was first symptom, then super slow speed that a new a sensor cured.
Try the unloader valve on the bottom of the main valve.I my experience they have not been a problem but if that is stuck then it will dump enough pressure to give you 2500 psi.