Excavator hydraulics


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Golden Jubilee
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Post Fri Feb 03, 2017 1:16 pm

Excavator hydraulics

Do any of you know/have experience with excavators? Have 1992ish Deere 290D,the under carriage moves but the boom/bucket do nothing and neither does the swing. From the way I interpret the manual the issue seems to be in the pilot circuit(?).
Any insight will be appreciated.
Last edited by Scottso on Sat Feb 04, 2017 2:50 pm, edited 1 time in total.
12 yrs.exp. in IH dealer parts dept.
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Golden Jubilee
Golden Jubilee

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Location: Lyman, IA

Post Fri Feb 03, 2017 2:48 pm

Re: Excavator hydraukics

Let me 1st say I don''t have Deere experience on the model you have, but I'm guessing the controls are electronic proportional control type. With this type of control, the joystick is not connected to hyd valve directly, but sends a square wave signal to the solenoid coil on the valve in question. The greater the signal the more the spool was shifted by the pilot pressure. This is how the manlifts I worked on did it.
Therefor there are 2) 1/2's you have to rule out. In the hyd side, there is a pilot pressure used to shift the spool in proportion to the signal from the joystick, and the other 1/2 is the electric. There is also often a "dump" valve to act as an emergency stop of all functions if the operator leaves the seat.
The drive portion is often a hydro-static drive system, as it allows a lot more torque than a proportional valve would, and would be separate from the digging controls.
With the drive functioning, but the digging controls all in-op I would first look for a safety interlock problem, then a dump valve.
I really think you are going to need a manual as these systems are not simple.
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Golden Jubilee
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Post Sat Feb 04, 2017 3:07 pm

Re: Excavator hydraulics

I have the manual but,was hoping someone had hands on experience with excavators so some of the steps in diagnosing could be skipped.Plus explain things in layman's terms since it's quite evident the manual was written by engineers.

This thing has "wet" joysticks and travel controls which Deere calls pilot controllers/valves. Not much in the way electrical in the hydraulics at all,some sensors and a couple of solenoids it appears.
12 yrs.exp. in IH dealer parts dept.
Never argue with a fool...
If you don't have anything nice to say...say nothing.
If you don't learn something new everyday...you weren't paying attention.
THINK! Be sure brain is connected before mouth is in gear.

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Sat Feb 04, 2017 4:44 pm

Re: Excavator hydraulics

Ok, Sorry not to have exactly the experience you need. Only thing I can contribute is that a loss of all boom functions points to a safety/pilot problem. Otherwise it would tend to effect only one function.
Do you know if this has a gear pump or piston?
Hyd can get quite complex. On the manlifts, they had a gear pump with a sequence valve that would have a pilot pressure about 400 psi above the "system" pressure. With the valve in "neutral" the pressure with the dump closed was only 400 psi. as a function was selected, the pressure would begin to rise, but the pilot was always 400 psi above the system. The more load the higher the pressure would get until relief pressure was hit.
A stuck or inactive dump would leave no pilot pressure to shift the valve. In a wet stick system it may be different.
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Golden Jubilee
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Post Thu Feb 09, 2017 9:42 pm

Re: Excavator hydraulics

Since you asked CB,it has geared pumps,3 to be exact. Personally I have a hunch it's in the pilot pump,we'll see...
It's a friend doing the job but since he's not all that internet savvy I do things like finding info. I also work on stuff with him when needed.

Would you happen to know anything about 4cyl. Perkins diesels? It's a 4.203-2 in a fork lift.
Looking for timing gear info,he thinks it may have jumped but I don't think so.The owner decided to play mechanic and change out the injection pump,needless to say that didn't workout well and now it won't start. It's been bled,filters are new so I think it wasn't at TDC when they put the "new" pump on. (I found that much info on the net).
I figure with all the farmers etc. here someone might have what I'm looking for since the engine was used in MF ag equipment.

This is the manual #
601 TPD 0580 1158 workshop manual
12 yrs.exp. in IH dealer parts dept.
Never argue with a fool...
If you don't have anything nice to say...say nothing.
If you don't learn something new everyday...you weren't paying attention.
THINK! Be sure brain is connected before mouth is in gear.

Golden Jubilee
Golden Jubilee

Posts: 5170

Joined: Thu Nov 29, 2012 9:28 pm

Location: Lyman, IA

Post Thu Feb 09, 2017 10:01 pm

Re: Excavator hydraulics

The Perkins we had all had CAV DPA injection pumps. I doubt it jumped time also, it would need to strip gears to do that. I know on the Leyland 680's (different engine) it was possible to install the pump wrong in the coupling. Some had one spline filled in so it would only go together in one position, but others didn't have that feature any were easy to get out of time. I don't remember how the Perkins did it.
If you have an old injection line you can sacrifice, you can make a tool to get you close. Cut the line at a 45 deg angle and remove the delivery check in the outlet of #1 on the pump, attach the line and bend it so it ends facing up, crank over by hand slowly, and when a drop of fuel at the end of the pipe appears, check the timing marks. IIRC the delivery check is either in the banjo bolt or the pipe extension on the DPA distributor block.
If there are no timing marks or they aren't accessible, You'll need to pull #1 injector and "feel" for top dead center by pressure and than mark something and back it off a bit to fire before TDC. It will get you close enough to run.
You might try over on smokstak forums for more help with both problems.

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