3 position, 4 way valve, cylinder in one direction only

I have a single spool valve that came cobbled onto my MH tractor, run off a pto-mounted pump. It was in line to run a double acting cylinder, but I'm just assuming that cylinder went up AND down. I've plumbed this valve to run my homemade 3 point da cylinder. But the cylinder only goes up, in one position on the valve, and not down using the other position. If I switch hoses to opposite positions on the cylinder, the same position on the valve makes the cylinder go down, and not up, so the valve is only pressurizing one of the work ports. What's going on with this valve? It doesn't seem to send fluid pressure to the cylinder in one of the two positions. I'm assuming its an open center valve because the center position is returning fluid to the reservoir. Also, only one position on the valve is spring return to center. The other is just "put it anywhere, and it stays" - no detent or spring return. I can't find any numbers on the valve.

Are the ports labeled? Something like P, T, A, B? Pump, tank return, cylinder, cylinder.

Is that the way it is plumbed?

If they are not marked, it may not be plumbed correctly.

The failure to return could be a clue, possibly the return springs is broken and jamming the spool.

The valve can be taken out of circuit, the flow checked with compressed air, taken apart, the springs checked. Once the function and flow are
determined, you can decide if it can be made to work.

Can you find a name and/or number on the valve. If you can google it. You may find schematics and instructions.

The ports are all marked and plumbed the way they are marked. I did find a name and casting number: Greshen 9 25 B (or 8). I'm about to look it up. I did pull the spool apart before I hooked it up and nothing appeared broken or bad. I'm new to hydraulics so I'm sure there will be some easy way to fix this, once I find out the what-for! It might be in the bypass, which I did not disassemble, yet. I am confused that one position does not spring-return to center.

I have several valves that look almost like that. The hex head between
the lever and the hose on the pic came with 2 versions, one for one way
operation and the other for two way operation. You very likely have the
one way plug installed. Google the name on the valve and yo will likely
find the solution. These plugs control the internal oi flow.

HTH

Thank you Areo. I'm having trouble finding anything on Gresen valves. Anyone have a link that will help me find a schematic on this old valve?

Here's what I found behind that plug. Can't find any of the missing pieces, but the A cylinder port is right next to this valve inside. I'm going to look downstream. Luckily its pot metal and not steel. However, I have no idea how, or where to find a replacement part, and don't even know what it's called, other than a plunger valve holder??!! The Gresen valve has a J 8 stamped on it that I missed the first couple of looks.

I pulled the spool out again, and discovered one mistake I made on reassembly last time. At the end of the bore that houses the return spring, there are TWO snap ring grooves. No telling what the outside one is for, except it is not the right one! Once I moved the snap ring to the inner groove, both positions spring return to center. I also built a new holder for the valve thingy opposite the pressure relief assembly, but that did not cure my "up but no down" problem. Still scratching my head but I think Areo has it right - the valve that I fixed probably makes it a power-up, gravity-down single spool valve. The cylinder will gravity down with a little weight when I use what should be the "power down" position on the valve. Any help would be appreciated on making this valve work both directions.

Just a few thoughts.

Parker acquired Gresen in 1999, so you should be able to get info from a Parker Hydraulics dealer. Hard to say what kind of luck you will have finding the parts you need, or the cost if you do find them. I like to reuse things like this myself, but sometimes just getting a new or used valve may be easier and more cost effective.

The 3 point hitch on most tractors doesn't have down pressure, they are single acting (up only). As you are plumbed would be correct operation for a common 3 point. Removing the return hose and plugging the port on the valve and putting a breather vent in that port of the cylinder might let it lower quicker. Right now it has to pull oil back into the cylinder to lower.

Does the pto mounted pump prevent using any pto driven equipment while the pump is in place? Does this current hook up have its own reservoir or is it using the oil in the transmission case? The pump and valve arrangement you have may have been installed to run drawbar pull equipment with a remote cylinder on the equipment, many such remote cylinders were single acting.

Thanks, Jim. The pump was mounted on a PTO coupler, with its own tank hanging off the back of the 1946 MH 101 Jr. It was hooked up to run a homemade front plow blade on a 2 way cylinder, but the first thing I did when I got the tractor was pull all that cobbled up mess off the front and back. Once I rebuilt the tranny, and got it running well, I found a NOS pump that directly mounted to the qovernor gear, so I'd have live hydraulics. I'm building a hydraulic 3 point for it, hopefully with down pressure to grade my road with a back blade. I'm building it stout enough to take the down pressure on the components.

I will call Parker, they have a store nearby, and I was aware they took over the Gresen brand, but didn't know when.

I was able to make a new holder out of brass (stronger than aluminum) for that poppet kinda valve, so replacing that part is no longer an issue. However, if the spool itself is only designed with one of the two work ports to be pressure, I will need a new valve to do what I want with the cylinder. I'd really like to find a schematic for this J-8 valve to know whether it can be converted to two way or not.