I am helping a friend of mine work on his excavator. I will try to explain what is happening the best I can. When you boom up with out the rpm's up it will work fine but when you turn up the rpm's the boom will work really slow and you also can hear some kind of noise coming from the area of the control valve. The noise sounds like something is bypassing. We don't have any books to help out. So maybe somebody can help us. Thanks
Sound like you have relief valve stuck open, a spool valve hung upor a pilot problem.I will email some info to you.What is your email address? Thanks ED
[email protected] Thanks Ed
Check your email .I sent you over manuals .
Got them thanks. Will let you know what happens. Thanks again
Hey tool king would a bad pressure reducing valve or a pilot pressure regulating valve cause the boom up to be slow or if they were bad would all the functions be slow not just one Thanks Donnie
Donnie dumb question the hydrualic tank has the right amount of oil in right.I am just reading the out the the manual for a 120 - 160 machine. I know checked it but sometimes the simple things get over looked. You know your suction screen in the hydrualic tank and pilot filter could be clogged up .These would slow things down alot.If you are going the check suction screen in hydrualic tank it might be a good idea to swing machine so tank is between tracks and drain into open clean drum .Then you look into tank and see if debri is stuck to suction screen .Because if you pull screen with oil in tank the oil may wash off debri as you pull it upif it is light .You might the problem .I have found all kinds of things in tanks .Not just hydrualic tanks mostly fuel tanks.It would blow your mind.If you need help call me at 1-201-832-1606 .I will try and help you over the phone if I can. Thanks Ed
So it needs a hydraulic filter but we had a leak in the cover of the variable pressure compensator valves when I got the cover off it has a bad o ring but I also noticed that two middle valves where stuck in. So I took them out one by one and cleaned them when I put them back in they still seemed to stick the other two moved freely and when you push in on them they did not stick. So I am wondering if that could be a problem. Thanks Donnie
Does the auto idle function work on the boom? Did you check the pilot pressure switches?
I don't know on the first one and no on the second
dbags89 I if you have a sticking spool it mess things up for sure .Are the spools from the ones that move easy the same size as the stuck ones .Use the good ones to check the spool block.You could have a bent spool or warpped block sction .I had that on a jcb wheel loader.Call me at 1-201-832-1606 if you need help. I can help you on the phone may eplain it better.
The pilot pressure switch tells the pvc when you pull a lever,, it tells the solenoid bank what to do with the vpcv,the auto idle is just a quick way to check the switches
Toolking do you know where i can get an EPC (engine)controller for the JD490E for a good price? In the US
Try swapping the circuit reliefs on the boom section top to bottom and see if your problem changes
I have a 490e was traveling extremely slow (like barley moving) , finally found a stuck spool in a solenoid valve , you can test that with a gauge on the pilot line for the proper function that is not working correctly , mine had 800 lbs psi at idle and was supposed to have 398 at full travel.
I have 490E has a slow stick only. if you surge or bounce the boom it will take off and move. works intermittently some times. I can hear something bypassing in main valve until stick goes. seems a bit weak in and out. Everything else about the machine works fine. in need of some service manuals. thanks, Daniel
sounds like a bad connection to the arm pilot pressure switch which is in the flow regulator valve behind the cab and under the tin plate (tool box where you keep your grease, bucket teeth ,big rocks that you found) There are actually 4 pressure switches under there .The arm in pressure switch is on the other side of the valve you are facing. Swap that out for the pressure switch on the other side(boom raise ps) and see if your problem changes.
Welcome to HEF Dwallace ! Might I suggest the next time to start a new Post rather than piggy backing off an old one.
ok, I swapped the (ps) from first valve closest to door too the back valve. made no difference in how the machine functioned. unpluged all (ps)s. still no difference. seems the machine will function if there is pressure against the boom. run the stick out until weight of bucket is on it. then it takes off and goes on out every time. bring it back in gravity at speed too the bottom then wait for it very slow until pressure against boom. bam takes off power and speed.
could variable pressure compensator valves be the problem?
Anytime I have one function that works slow I always try to eliminate the cylinder first with a leakage test, then the circuit reliefs next (usually by swapping them with another). Then I would make sure pilot pressure to the arm caps on the control valve are up to spec. Those are the simplest things to check. After that the possibilities on those machine's get quite complicated.
yes, cylinder checks out good. fresh seals will hold a load overnite. circuit reliefs must work because it'll dig. pulls motor down but not to stall. my thought is how does it function with all 5 (ps) unpluged? must have computer bypass or something. I bought from farmer who had been running it like that for years. computers are flashing. auto idle works for every function. modes seem to make a little difference when switched. when I activate stick in or out I hear a wine from main valve. like staved for oil. until bounce or surge the stick. bam speed and power like it should. every once in a while it'll work without surge like main boom up stick out same time or bucket curl. seems odd it could function with all (ps) too both valves behind cab unplugged. made no difference in function of machine. I expected boom to stop as we unplugged switches. I have 24 volts to solenoids. maybe I'll pull cover plate were steel control line for stick goes into main valve. I very much appreciate anyone's thoughts on this issue. or service manual for this machine john deere 490E. thanks, Daniel
It still functions because it uses an angle sensor for pump position and a differential pressure sensor to know when a function is activated. The pressure switches for lack of a better explanation are for fine tuning of the operation. You will always have 24 V to the solenoids. The PVC controls the grounding of those solenoids. At this point if you want to perform your own repairs I highly suggest you have the owner buy you the TM1504 Tech Manual. You won't find any free manuals out there unless somebody out there has one to share. One other question, does this machine have a controlled lowering device on the boom (see below)?
no sir, hoses from stick cylinder attach too main valve. boom works as it should. did find a broke wire at tank switch but seems this wouldn't cause just one function to act up. I would like to see a diagram of the variable pressure compensator valves. looks like all the steel control lines have to be removed along with most of the lines feeding the boom. to access the cap bank just like to know I'm looking in the right place. I did drain tank had some water in it. cleaned filter wasn't bad .also pilot filter had some paper element material in it. pilot control has been rebuilt by JD. made no difference. if any pressure at all is applied to the stick it works. but if you let everything come to a stop with stick hanging down it'll barely move sometimes not at all. rpms make no difference.
What's your serial number? Sounds like you are having an issue with load sense pressure getting to the DP sensor. Maybe backprobe terminal #2 of the DP sensor and measure the voltage with the key on engine off, then with the engine running with the levers in neutral and then with the arm function activated with your issue happening. Then try it with the boom activated to compare. If there is no change in the voltage when the arm is activated then it would confirm the lack of load sense pressure getting to the DP sensor. With the levers in neutral and engine running you should see about 4.5 V. With a lever stroked it should drop.
FF490EX026327 Yes sir, that's what it seems like. I also noticed there is another pressure switch on the bottom of that spool( stick in and out ). should there be voltage there as well? I can hear a valve bypassing when function is activated. until pump is stroked (usually by another function)then arm takes off. when I drained tank found the screen and mounting rod laying in the bottom of tank. no telling how long it's be there. lots of snot on it. oil very milky. found paper material in the pilot filter. probly from someone washing out main tank filter. worried debris has got into main valve. I'll try the ps voltage test first. is there anyway to check or test spool under the control lines without removing them? if I were to hook a gauge to the steel line going in. activate function I should see a pressure spike? how much? thank you very much for helping me with this machine.
The only way I can think of and it's only a maybe is to tee into the pilot line on the cap and slowly activate the function. If the spool is sticking I would think it would rise gradually then drop when the spool moves from it's stuck position. A spool that is moving will never have a drop, just a gradual rise. Check the DP and post results.
finally ,got a chance to work on the old hoe. unpluged the dp sensor. 3 wires coming to connector. outside wire has 5.1 v center 0v other outside 0v. machine still operates the same with dp sensor unpluged. machine running made no difference. didn't see drop when activated. should i scrape the wire and test with it pluged in?
Please re-read post #25 and test DP voltage like I asked. You do not want to test with it unplugged. You will need to backprobe (carefully) the wires at the DP connection. Also, check your arm in pressure switch and your arm cylinder head end pressure sensor for proper operation.
yes, I back probed term 2. found 4.1 -4.4v when activated lever voltage drops. the more pressure against bucket the lower the volt too .6v except for stick in. volt s drop slightly 3.3v until boom comes to hard stop then volts drop to .6v I can tell pressure builds also. stick out volts drop a little more 3.1v boom moves a bit faster but both are weak until end of stroke then full pressure. this must mean poor volts from ps ?
there is also a ps on the bottom of that spool. should it send voltage too dp sensor?
At this point I think you need someone with MPDr to connect to the machine to check the readings of all the sensors and to see if there are any codes.
will the computer flash codes? got to be a way to self diagnose
I read somewhere there is a way to use a jumper wire. get the computer to flash codes?
The reason I recommend an MPDr hook up is because you might have an on/off switch that is not working or a sensor that is not correct but still within parameters, either of which will not trip a code. It is a quick way to eliminate electrical issues and is easier than diving into a hydraulic issue. If you are looking into the 4 pin diagnostic plug with the lock tab up you short the right side upper and lower terminals together, then turn the key on to get the blink codes. Make sure you are reading the blinks on the PVC and not the engine controller. Report any codes found. I highly recommend you get the Operation and Test manual TM1504.
what is the correct way too test pilot pressure? connect to steel line at cap? with tee or dead head into gauge. what pressure should I see at that point? with the back probe test. am I reading voltage coming from (DP) or going too (DP)? if I'm seeing voltage from sensor. does this indicate poor pilot pressure? any help is greatly appreciated..
Test the pilot pressure by "teeing" into the line that goes to the spool for your problem function. The pressure should rise and fall smoothly as you work the lever. Full stroke of the lever you should see 740 - 880 psi. The 5 V supply voltage comes from the PVC and goes to the DP sensor. The DP signal voltage (should be green/white wire) would be voltage coming from the DP sensor going to the PVC. You should see a varying voltage and the voltage should be approximately the same at various points of operation of any function. The movement and load of the function will most likely be different on different functions and therefore different voltages. A dead headed function going over relief, no matter which function, the DP should be reading approximately the same. If you are having trouble with only one function then the DP is not your problem. I was just trying to use the voltage to try and narrow down the issue. Lets ignore the DP for now. I mentioned this before, I highly recommend you get the Operation and Test manual TM1504.
490e and 790e will drive you nuts. I used to talk to a guy named Ken Hutters at DTAC and he was the smartest engineer they had.He saved my ass many, many times.Those machines were the first computerized machines on the market and were a steep learning curve for us guys that grew up with the old simpler stuff.By now I would assume that the wiring in that thing is toast so your advice to get the manual will save a ton of time and money.
ok, i,ve got poor pilot pressure to the spool 500-550. also checked other spools 900-950. must be a regulator in that system. were to check next? can i bypass the little block that the cap lines come from?
I swapped pilot lines at cap. problem stayed in same spool.(stick) are there o rings that can be replaced under that cap? or should I be looking at pressure compensation valve? I got my pressure reading with tee at cap. when I swapped lines, stick became boom. and pilot in question operated it perfectly. so I'm purdy sure it's in that main valve.
Hey Ed. Can I get my hands on those manuals you spoke of? Having a hydraulic issue with my 490e also.
What's your email ?
Dm’d you.
Thank you Ed!!
Hello Dwallace did you ever find the problem with your John Deere 490? I am having almost the exact issue with my Hitachi gray-market 200-3