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Curtis B.
Curtis B., Technician
Category: Construction and Road Equipment
Satisfied Customers: 26530
Experience:  Technican turned service manager with multiple lines of equipment and rental units.
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I have an old Marklift J20NEP scissorlift. It was working

Customer Question

I have an old Marklift J20NEP scissorlift. It was working fine. Then one day I went up and then came down. Fluid just poured out of the fill pipe! Then, no longer would the lift go in forward or reverse. It wants to, just no poop to get it going!
Submitted: 9 months ago.
Category: Construction and Road Equipment
Expert:  Curtis B. replied 9 months ago.

No hydraulic functions? Is the pump motor running ? If it is, and no function, remove the pump from the motor and check the coupler between the two.

Customer: replied 9 months ago.
The pump is running. The lift tries to move forward and reverse. It just doesn't have the poop to do so. It also goes up and down just fine!
Expert:  Curtis B. replied 9 months ago.

Dump valve in the hydraulic manifold is stuck open, not letting pressure build in the drive function. Broken spring or stuck valve.

Customer: replied 9 months ago.
OK, do you have prints of this unit as I do? There is a solenoid on the drive dump valve. One wire, so I assume the other side of the solenoid goes to ground. There is a large nut on the end. Do I remove the nut to pull the valve and solenoid? O rings there? Do I replace the whole thing or do I just read the solenoid (what should it read in ohms?) to see if it is open and replace it if it is?
Expert:  Curtis B. replied 9 months ago.

No , I don't have the diagram. But the large nut should only hold on the electric coil. The actual valve is under it, and will screw out of the manifold.

Customer: replied 9 months ago.
Well so far, you may have been expremely helpful, Curtis. I will go pull it now. I would expect the solenoid to pull the valve one direction and the spring to push it the other position, though I am still a little unclear. Or the valve is just stuck in the center position with the coil unable to pull it and the spring unable to p[ush it. Wish me luck!
Expert:  Curtis B. replied 9 months ago.

It think it is all in the solenoid valve assembly and is a small pin, type valve in the assembly!

Expert:  Curtis B. replied 9 months ago.

I assume you are getting voltage to the coil and it is making a magnet?

Customer: replied 9 months ago.
I have pulled the solenoid and the valve. The one thing that is apparent to me is that the two O rings together at the end of the valve are dry and flattened. And, they look flattened to the point where fluid could bypass them. Now, I have O rings. I have two thicknesses. The smaller ones are the same size as the old ones. The larger ones are about wice as think. Should I continue to use the double-up of the smaller ones or go to a single fatter one... or even two fater ones. My thinking is that the solenoid is Ok because the lift DID try to move in both forward and reverse. Do you agree?
Expert:  Curtis B. replied 9 months ago.

Does the pin in the valve rattle around if you shake it? I would go back with same size o'rings that it had.

Expert:  Curtis B. replied 9 months ago.

Did you find the problem?

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