Crown 20MT Walkie forklift (lift-lower valve problem)

[js5020]

Sodo,
Not exactly sure how the Parker solenoid valve is made but it has at least one sealing surface and possibly two. Since you say the valve is working perfect does that mean it lowers electrically? Parker DS091C D012HP valves are 3/4-16 threads and have .623 diameter nose for sealing in a .625 diameter hole. This is an odd ball cavity so finding a replacement valve may be difficult.

A concern I have with this electrical valve is what is controlling the lower speed when using the electrical. Is there a metering orifice in solenoid valve or some restriction below the valve. The DS09 is rated @ 5 GPM with @ 70 PSI pressure drop so this would allow the mast to free fall which is not good.

If you want to experiment: Remove the solenoid valve and look at the drill diameter below the valve cavity. Is the hole around 3/8 to 7 /16 in Diameter? Is the nose of the cavity reasonably smooth? If yes get a 1/2" diameter steel ball and a #8 SAE fitting. Put the ball in the hole install the fitting and operate the lift. The ball should seal on the nose of the cavity similar to how the check valve ball seals. You may need a soft spring to hold the ball in place.

This would help identify what is leaking.

Ditto what oldnslo said or plumb in a shut off valve on each the lines. Just dont "deadhead" the pump, I dont think that pump has an internal relief.

 

[Sodo]

Sodo,
Not exactly sure how the Parker solenoid valve is made but it has at least one sealing surface and possibly two. Since you say the valve is working perfect does that mean it lowers electrically?

Regarding the walkie's operation, every button, valve, function works perfect, so I am assuming the solenoid valve is working.
The ONLY problem** with the entire forklift is (with a load) it creeps down an inch every 5 seconds.

A concern I have with this electrical valve is what is controlling the lower speed when using the electrical. Is there a metering orifice in solenoid valve or some restriction below the valve......allow the mast to free fall......

Noted-good call thx for mentioning that. Will look @ circuit & valve for a down flow control before considering a substitute to OEM solenoid valve.

If you want to experiment: Remove the solenoid valve ..........try .... 1/2" diameter steel ball and a #8 SAE fitting ......& spring.......

Great suggestion to isolate the 2 valves, will have a look at that option. Thanks!!

 

[oldnslo]

SoDo,
For reference this is my best guess on the hydraulic schematic in the manifold. I don't recall ever seeing a relief valve in any of the pictures and I also am not sure where the lower speed/flow control is located. For safety I would expect it to be at the cylinder but not positive on this location.

 

[Sodo]

Yes Oldnslo that schematic looks correct. The only thing I see different (and it is outside of the manifold) is from the top of the lift cylinder there is a small return line to the tank. Also where is the flow control, and wouldn't there be one control (for the case where both valves are open at the same time)?

You have drawn the 2 valves with a check in them. The manual lower valve has a seat that would function as a spring-and pressure-activated check. The seat appears to be perfect. I suspect the manual lower valve is rarely used. On the Solenoid valve, I can't see the 'seat', iand it doesn't look like this valve can be disassembled. I will take it apart again and look at these carefully. Are there any pics that I should take? Closeups of the valves?

 

[aczlan]

On the Solenoid valve, I can't see the 'seat', iand it doesn't look like this valve can be disassembled. I will take it apart again and look at these carefully. Are there any pics that I should take? Closeups of the valves?

The solenoid valve probbaly doesn't have a "seat" as it blocks/unblocks holes in the side of the valve rather than pushing on a seat. Its "seat" is the side of the hole that it goes into.

Aaron Z

 

[Sodo]

The solenoid valve probbaly doesn't have a "seat" as it blocks/unblocks holes in the side of the valve rather than pushing on a seat. Its "seat" is the side of the hole that it goes into.

Aaron Z

I see…. thanks Aaron. I will look at that. Like a shuttle valve that pressure does not energize? Makes sense then that it could wear out and leak since it's not pressure-energized.

 

[oldnslo]

On the Solenoid valve, I can't see the 'seat', iand it doesn't look like this valve can be disassembled. I will take it apart again and look at these carefully. Are there any pics that I should take? Closeups of the valves?

SoDo,
Usually the solenoid can be dismantled IF you have access to collet to grip the nose or cage. Look closely at the connection between the cage and retainer threaded area. Does it look like these are two seperate pieces? The cage in most cases unscrews from the tube assembly. This joint may be loctited. See the attached data sheet on the Delta Power valve. This valve has TWO sealing points. One is the pilot pin to the main poppet and the other is the main poppet to the cage. Both of these are metal to metal seats.

NOTE: A couple of companies may have the tube assembly unscrewing from the retainer or mechanically staked this joint so they cannot be dismantled

If this was a spool valve like azclan described it would always leak some.

The flow control in the schematic is in a location unknown to me. I suspect it is in the cylinder or the cylinder line since this would be the best place for safety reasons.

 

[Sodo]

If you want to experiment: Remove the solenoid valve and look at the drill diameter below the valve cavity. Is the hole around 3/8 to 7 /16 in Diameter? Is the nose of the cavity reasonably smooth? If yes get a 1/2" diameter steel ball and a #8 SAE fitting. Put the ball in the hole install the fitting and operate the lift. The ball should seal on the nose of the cavity similar to how the check valve ball seals. You may need a soft spring to hold the ball in place.

This would help identify what is leaking.

OK I eliminated the solenoid valve. I put a fairly tight-fitting bolt, with an o-ring around it, into the hole. The spring for the manual valve on the other side, pushes against my 'plug bolt' which is also energized by hydraulic pressure. See this in the pictures attached below.

The walkie still creeps down!

So I guess the Solenoid valve is not the problem. The manual valve is a 45deg seat, is pressure energized, and appears to be 'perfect'. I'm pretty sure the hold valve (ball-check) is perfect too. And the return tube from ABOVE the cylinder packing, is DRY. There has been no fluid passing thru it in a long time so I conclude the cyl. packing is 100%.

As if I wasn't stumped before now I'm really stumped. Its like the manifold has a crack or void or something.

 

[J_J]

Sodo

Maybe you have already done the cyl check, but

You seem confident that the cyl is not bypassing and the problem is the valve..

Have you put a needle valve in the base end cyl port and raise the cyl with a load and close off the needle valve and see if the cyl will hold. If it does hold, that will tell you that the cyl piston seal is good, and it is indeed that the lowering valve is faulty. .

 

[Sodo]

JJ, I have not done a cylinder check, and my reasoning may be faulty. I tried to explain it in page1 but let me try again.

Pressure comes into the bottom of the cylinder, and is released from the same port at the bottom of the cylinder. At the top of the cylinder there are some return ports to return any fluid that gets past the cylinder packing. The packing is new, replaced a few months ago.

If the cyl piston seal was leaking then the fluid would be above the piston, and when you extend the cyl to the top, this fluid would be forced thru these tubes, and return to the reservoir.

But when I remove any fitting and look, its dry inside. If I tip the hoses down, not one drop comes out. If there is any fluid getting past the piston, it's not enough to wet the hoses, and that is not possible because it will creep down from top to bottom, and in that case there would be the entire ram's volume passing thru these return hoses.

That's why I say the packing is 100%. What do you think, does this observation eliminate the packing as a possible cause of the creep?

I really appreciate you guys helping me on this. I have not done much with hydraulics but I'm enjoying the learning part. The losing part it isn't as much fun.