Troubleshooting Rolling Bridge Jack

[olds70supreme]

I bought a lift w/ two rolling bridge jacks recently and one of the jacks (as disclosed by the seller) doesn't work. The seller thought the air motor/pump was the issue, as the other jack had been retrofitted with a new pump and it works fine. I raised it up manually and looked at it last night for the first time. When I put air on it and turn both handles to raise it, the air motor makes noise that sounds like it should be pumping (clicking noise) but nothing happens. The unit had fluid up to the cap fill cap/breather. I haven't dealt with anything like this before so I had some questions about troubleshooting...

There are no markings on the unit - is it possible to visually ID the OEM? I'd like a manual if available. A lot of the questions below would be solved by knowing who made it...

It looks like there are two main parts - a hydraulic pump and a jacking cylinder. I'd like to rule out the cylinder, is it ok to disconnect the hydraulic line from the pump and put, say, 30 psi air pressure on it unloaded to see if it moves? If it does it would indicate the pump was the issue.

Can I test the pump by putting a pressure gauge in the line between the pump and the jack? How high of a pressure is typical for these?

IF the pump or the jack, are these typical DIY repair jobs, or do these get sent in to specialty shops for rebuilding?

 

[cubfarm 1]

You can use full air line pressure on the cylinder with no harm, it it runs at over 3000 psi.I doubt it will lift at that pressure!!
It is possible that the pickup screen at the bottom of the pump unit is plugged with fine debris. It is also possible for these pumps to loose prime.. Light air pressure with a rubber tip air gun while running the pump can cure this. Doesn't take much air. Pump may have an ID on the side of the housing on top of the plate that bolts/screws to the fluid tank. If the air motor side is shuttling the fault is then in the pumps pressure side. Warning--- many tiny parts!

 

[cubfarm 1]

No name pumps are on ebay cheap. You can match up a pump by pictures.

 

[engineer2]

Some of these air hydraulic pumps are also installed in semis to lift the cab up for service
Truck repair place might still sell them.
Post up a pic of the pump if you get it out. I have an NOS one in the basement.