Looking for hydraulic troubleshooting help.

[jmlcolorado]

Hey folks. I bought a stupid cheap scissor lift to help build out the interior of my 40x48 shop.
I got it for $900 as the guy was moving out of state and he needed it gone. He stated hat it won’t move under its own power up and incline. It will lift/lower and turn both left and right with no problems. The wheels do attempt to rotate with the forward/back buttons activated and will move on totally flat ground.

I bought a 3k psi pressure gauge and tested the oressure at the valve box as indicated in the manual. It reaches the required pressures at the valve body in all functions. My next assumption is that the wheel motors are going bad but I am Not familiar enough with hydraulics to have proper direction as to what to look at next.
Can anyone assist?

This is a MEC model Naro 20 lift.

 

[tom-ky]

Without seeing the schematic for that unit it is hard to say. Should be a relief valve in the propel circuit, it can be off, blown O-rings or motors. Does it have a single section pump or multiple? I have seen one section get wiped out. Also need to verify the brakes are releasing on it.

 

[jmlcolorado]

Without seeing the schematic for that unit it is hard to say. Should be a relief valve in the propel circuit, it can be off, blown O-rings or motors. Does it have a single section pump or multiple? I have seen one section get wiped out. Also need to verify the brakes are releasing on it.

And here’s where my ignorance comes in. I have no idea how to tell a single section pump vs others.
The brakes are currently disconnected and verified not hanging up. I presume the previous owner disconnected them during his attempt.
Here’s the only manual I could locate online about the machine.
https://www.mecawp.com/wp-content/uploads/2017/04/7053_Naro20-OP.pdf

FYI, I did buy new batteries and charged to full capacity before troubleshooting.
Hopefully the attached screenshots from the manual can answer your questions (obviously except relieve valve condition).

http://imgur.com/a/lTShKRu

 

[Farmall 1066]

I'd look for a tow valve that may be partially open.
Jack it up and see if wheels turn freely by hand. Should be some resistance.
If you stall it against something, or chock the wheels and try to drive, do wheel motors or pump get hot? Heat indicates internal leakage.
Bad part is, if one of these is bad the rest likely isn't far behind.

 

[jmlcolorado]

I'd look for a tow valve that may be partially open.
Jack it up and see if wheels turn freely by hand. Should be some resistance.
If you stall it against something, or chock the wheels and try to drive, do wheel motors or pump get hot? Heat indicates internal leakage.
Bad part is, if one of these is bad the rest likely isn't far behind.

Thanks for the pointers. I will try your methods tomorrow and see what I come up with. I havnt wanted to lay on the drive function for too long.
Think it would be worth removing the counter balance valve and seeing if a hydraulic shop might be able to match up a replacement?

 

[tom-ky]

There can be orings blown on any of the control valves in that circuit or anywhere that is seeing the pressure. Are all the controls working properly electrically in the propel circuit?

 

[jmlcolorado]

There can be orings blown on any of the control valves in that circuit or anywhere that is seeing the pressure. Are all the controls working properly electrically in the propel circuit?

Both forward and reverse are equally weak. Which brings up a good point. It appears from the diagram there is one valve for forward and a second for reverse. These both would share the same circuit. If I remove both valves, are the o rings you speak of on the end of those valves or internal to the the valves?
Basically I’m asking if I remove the valves, will I find the o rings you are talking about?

 

[tom-ky]

Both forward and reverse are equally weak. Which brings up a good point. It appears from the diagram there is one valve for forward and a second for reverse. These both would share the same circuit. If I remove both valves, are the o rings you speak of on the end of those valves or internal to the the valves?
Basically I’m asking if I remove the valves, will I find the o rings you are talking about?

At the end of each valve there should be a nut so that the electrical coil would come off and then the cartridge could be screwed out of the manifold. Orings on the forward/reverse valve, brake valve decal valve or counterbalance valve could allow for lose of flow and pressure.

 

[crazylunker]

some earlier models had a spring loaded cylinder that acted as a brake. if you have one and the the seals are blown/rolled then that could also affect the drive circuit

 

[jmlcolorado]

some earlier models had a spring loaded cylinder that acted as a brake. if you have one and the the seals are blown/rolled then that could also affect the drive circuit

This one does have a small cylinder that mechanically releases brake shoes on the rear wheels. The cylinder does actuate in/out but is not mechanically attached to the brake linkage anymore.

 

[Milton Shaw]

Make sure its not just low on fluid and running dry when it's not level. Also check the release valve that allows you to move the lift by pushing/towing. It could be just partially closed.. Those lifts are very handy wish I had one and the room to store it.

 

[BukitCase]

"This one does have a small cylinder that mechanically releases brake shoes on the rear wheels. The cylinder does actuate in/out but is not mechanically attached to the brake linkage anymore."

That might be your problem; most industrial equipment attempts to be idiot-proof/failsafe - a lot of stuff I saw in 35 years in heavy industry wouldn't work if something was disconnected - crane and other lift brakes for example - ENERGIZE to RELEASE the brake. So if a wire breaks, you STOP til it's FIXED -

Don't wanna get your hopes up too much, but you might try to either tie that brake actuator in the same direction as it would get pulled, or just hook it back up... Steve

 

[jmlcolorado]

At the end of each valve there should be a nut so that the electrical coil would come off and then the cartridge could be screwed out of the manifold. Orings on the forward/reverse valve, brake valve decal valve or counterbalance valve could allow for lose of flow and pressure.

Okay well I opened Pandora’s box now. I removed the nut on the top of the solidoid and took it off. Kinda surprised that’s its just an electromagnet. Unscrewed the valve cap and exposed the assembally. I could only find one o ring that seals the cap to the valve block itself. This is a shuttle valve for forward/reverse movement. The valve itself appeared in decent shape but couldn’t find any other o rings other than the cap rings.

Upon reassembly, a nail fell out from inside the cap. Yes. A nail. With a head and a point. Tiny silver nail you’d use to hang a picture. I’m positive it came out of the cap as it was covered in oil and was all pretty shiny. Not the machine will only attempt to move in reverse no matter which way the switch is activated which tells me the shuttle valve is stuck.

I’m tempted to call a hydraulic shop and see if they would take the whole dang valve box and rebuild it for me. I’d simply remove it from the machine after marking all the line locations and take the whole dang thing to them to rebuild. Clearly, with a suspicious nail hidden inside, something isn’t right.

"This one does have a small cylinder that mechanically releases brake shoes on the rear wheels. The cylinder does actuate in/out but is not mechanically attached to the brake linkage anymore."

That might be your problem; most industrial equipment attempts to be idiot-proof/failsafe - a lot of stuff I saw in 35 years in heavy industry wouldn't work if something was disconnected - crane and other lift brakes for example - ENERGIZE to RELEASE the brake. So if a wire breaks, you STOP til it's FIXED -

Don't wanna get your hopes up too much, but you might try to either tie that brake actuator in the same direction as it would get pulled, or just hook it back up... Steve

I’ll give this a shot. I can push the brake cylinder in by hand when not activated. It slowly presses out when activated until it tops out. It’s not connected to anything and most of the linkage is missing. The brakes are totally free, but I understand your theory. Perhaps that cylinder requires pressure to allow full pressure to go to the wheels. Worth a shot.




P.s. here’s a video of me screwing around with it with the drive wheels off the ground.

 

[tom-ky]

Did you ever figure it out?