3 Spool Hydraulic Valve Won't Do Anything

[r8f1k]

I have a Case DH4B, just got the thing up and running where all the features work except the backfill blade. There are 3 pumps, one runs the forward and reverse hydrostatic transmission, a small one runs the steering and the backfill blade and the third one runs the trencher chain. There are two outputs from the small pump, one goes to the steering wheel valve and the other goes to a 3 spool control valve which runs the backfill blade. I have taken the valve out and gave it a good cleaning, I pulled the caps off and run solvent through it in my solvent tank overnight. It was a little sticky, but seems to have freed up more than it was. My questions is, how is it that NOT ONE feature works on the blade? I would think at least something would happen. You would hear a whine or a chatter or see a little movement from the blade. Not a sound or even a quiver of movement. The pump clearly works because it runs the steering and that functions as it should. Is it possible that the spool is in such bad shape that nothing will happen? If I run the machine for a while and get the oil nice and hot, will maybe help? Any thoughts are appreciated.

 

[oldnslo]

Two outputs from the small pump? Can you explain this in more detail?

Example: pump is double pump with two individual flow sections or
pump feeds a flow control valve that supplies flow to steering and flow to 3 section valve.

 

[r8f1k]

 

[r8f1k]

Above is the picture of the pump, a line can be traced to the three way spool. I am pretty sure that there were 2 ports out and one input line. If that is NOT the case, is it possible to run the backfill blade by tapping into the line that feeds the trencher chain motor? Like a 'tee' at the pump with one going to the trencher motor spool and one to the 3 way spool?

 

[oldnslo]

R8
It does look like there is a valve assembly in the end of the steering pump. Possible it is a priority flow valve where a preset flow goes to steering and excess flow is directed to three section valve. Is there any description for the parts breakdown on that pump?

Can you remove the tank line from the 3 section valve to see if there is any flow? If yes then shift a valve and see if flow stops.

 

[r8f1k]

R8
It does look like there is a valve assembly in the end of the steering pump. Possible it is a priority flow valve where a preset flow goes to steering and excess flow is directed to three section valve. Is there any description for the parts breakdown on that pump?

Can you remove the tank line from the 3 section valve to see if there is any flow? If yes then shift a valve and see if flow stops.

The tank line is shared with the trencher motor return. I think that would give a false positive...... Am I understanding you correctly?

 

[oldnslo]

Since tank is a shared line could you disconnect the pressure line feeding the valve to see if you get flow or an idea of how much flow. Then reconnect pressure line and look at tank line so you have an idea on how compares to pressure line. Operate a function and see if it changes. If yes this would point towards an alternate flow path before the valve. If no it would point towards an alternate flow path in the valve connecting pressure to tank. First place I would look in this instance would be system relief if in the directional valve.

 

[r8f1k]

Update: Took the machine outside and gave it a run through the paces. A couple other issues, but some success.
1) I made the mistake of moving all the hoses from the excavator control spool, to the new JOYSTICK spool, one for one, in the same ports, left to right. This gives a very random pattern, not ISO or Standard. I need to swap them around to make it right. Stupid error....

2) The pace of the trencher is a little too fast for the trencher to dig. There is a crawl feature, I don't really know how to use it.

3) Finally, the backfill plow now KINDA works. After really getting the machine hot and running a higher RPM, the blade will move left to right and tilt. It won't go up and down. When running the blade, she blew a 1/4" hose. It sprayed a bunch of white hydraulic fluid. I'm good with getting the old fluid out, but I have to repair the hose to see if anything else will work.

I am happy that the machine, which was dead for 10 years, is now 90% working. I have a couple long trenches for drain tile, service lines for power to a new building and some future intended projects.

 

[LouNY]

You will need your crawl speed to use the trencher. It's been many years since I ran a trencher
but as I recall I'd place the transmission in neutral and engage the creep drive which was hydraulic
driven, the activation was a fork that slid a coupling into engagement and transmitted the hydraulic
drive into the wheel drive shafts.

 

[r8f1k]

True. I don't really know how to adjust it. I have to take apart the entire steering column to replace a hose, rebuild the steering valve, getting the Forward/Neutral/Reverse lever unstuck.

The machine has a lever on the upper right dash panel that can be shifted into 3 positions.
Middle = Neutral, Up = Travel, Down = Work

Then, there is a shifter on the left side of the steering column for Forward/Neutral/Reverse

Does the machine simply get put into Neutral via the lever on the dash and then Forward on the column, lock the crawl?

Below is a diagram of the crawl mechanism.

(DH4B) - CASE TRENCHER W/2.1L ENGINE (1/79-12/91) (1-38) - STEERING WHEEL CREEP CONTROL INSTALLATION Case Constructuion

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