Hydraulic Power Unit

[htiek126]

I bought a Barnes 12 VDC hydraulic power unit with power up and gravity down (I belive it is a GC8000) on Ebay. Unfortunately it did not come with directions.

I rotated the pump 90 degrees, and I adjusted the oil pick up line 90 degrees to match the new orientation. I installed the pump on my trailer and it runs fine, but it does not develop pressure or hold pressure. The cylinder will bleed down with the pump in the neutral position.

Am I having trouble because I rotated the unit and the pump or valving is gravity dependent? Does this pump have an adjustable relief valve that perhaps is set too low? Or perhaps it is just a stuck check valve?

 

[jrlichina]

Do you have the check valve solenoid wired properly? The switch should have two buttons, one for "Up" and one for "Down". The "Up" button just energizes the pump and the "Down" button energizes the check valve to return the fluid to the resivor. Pressing "Up" should extend your cylinder and the check valve holds it in position until energized. The check valve may be defective, disconnect it and check to see if the cylinder holds position.

 

[htiek126]

This unit came with the manual knob integral to the unit that is an electrical switch to the motor solenoid for up and I believe is the mechanical valve for the down position. I have not changed anything on the controls.

 

[Anonymous Poster]

Possibilitys
1) defective valve
2) mispositioned valve handle
If the valve will hold the load when you manually hold the handle slightly to the lift position, without engaging power, your handle is slightly mispositioned. That is the usual problem with these units.

 

[htiek126]

I found some information at http://www.hydraulic-supply.com/pdf/1019.pdf.

According to this information I can rotate the components and it should still work. A strict interpretation of the hydraulic schematic agrees with your assessment exactly. The manual valve would be the only single component failure that could cause it to not develop or hold pressure. I did notice that the handle assembly was slightly lose, and I will check that tonight.

The information also says the relief pressure is adjustable from 1500 to 2500 PSI. Does anyone know how to adjust this pressure? I know there is a tall hex shaped bolt head sticking out where the pressure relief assembly is located. Do you adjust the pressure by turning this bolt head, or do you remove this assembly and tweak something inside?

 

[jrlichina]

There should be an adjustment screw under the hex head cap. Turn clockwise to increase pressure, add a guage to check.

 

[htiek126]

I took the manual valve apart and the valve stem fell out. It looks like a bolt with a tapered head to seal the passage, and it was completely unthreaded. I added some thread locking compound, turned it one half turn past making the seal, and it works great. Thanks for the help.