Where to place pressure gauge in simple open center system?

lhfarm · Apr 27, 2013

Back to working on my 1949 jeep 3pt lift that uses a power-up, gravity-down ram (the ram does have a "return hose" that dumps into the tank). Not many places to install pressure gauge, but assuming I should but in a tee just in front of the valve inlet. Assume I should take the high pressure measurement while extending ram.

I want to test both the pump operation as well as the valve operation. What should I observe at the pressure gauge that will tell me if the valve is operating correctly?

Any advice or instructions appreciated.

triptester · Apr 27, 2013

Place the gauge before the valve. Pressure readings will depend on the pumps rated capacity and the resistance to flow. With the control valve in neutral little to no pressure will show. Max pressure will read when cylinder is fully extended and relief in control valve is openning.

J_J · Apr 27, 2013

Install the gage in a tee in the IN port of the valve.

The gage will tell you the resistance to the pumps flow in PSI.

If the cyl and the valve is good and not leaking, the gage will reflect the force that the cyl is developing.

If you know the valves relief pressure, and can see it on the gage you can assume the pump is doing it's job.

lhfarm · Apr 29, 2013

J_J said:
Install the gage in a tee in the IN port of the valve.

The gage will tell you the resistance to the pumps flow in PSI.

If the cyl and the valve is good and not leaking, the gage will reflect the force that the cyl is developing.

If you know the valves relief pressure, and can see it on the gage you can assume the pump is doing it's job.

So I'm getting little or no movement on the gauge, at any time. But the lift does go up and down. I can lift my weight, but not two of us ~400 LB. It took a lot of cycles before it would lift anything. I removed the filler plug on the reservoir and it was pressurized - blow out a small amount of fluid. I think I finally have all the leaks stopped but not sure what to do next.

It did seem when it first started lifting me (after I had cycled it with no load several times), it worked well and the lift moved up quickly. Then it would only work some of the time, until I bleed it (see above). So I'm thinking the pump may be OK and the valve is just not working right all the time.

For now, I'm going to take the gauge out of the circuit and take it to the barn and try lifting a small 2-12 plow. If it does that, I'll declare victory.

Thanks for the help.

J_J · Apr 29, 2013

Are you sure you installed the gage in a tee in the IN port of the FEL valve?

Did you extend or retract any cyl to the max so the relief comes on.

If you have things connected correctly, you will show every psi the hyd system is developing.

If you did not see any pressure, then things are not connected correctly.

Rules are rules, and if the pump is good and the parts are good, then you will develop pressure.

Leave the gage installed, as it is a valuable tool for trouble shooting, and useful for monitoring the hyd system.

triptester · Apr 29, 2013

Normally the reservoir should be vented.

lhfarm · Apr 30, 2013

J_J said:
Are you sure you installed the gage in a tee in the IN port of the FEL valve?

Did you extend or retract any cyl to the max so the relief comes on.

If you have things connected correctly, you will show every psi the hyd system is developing.

If you did not see any pressure, then things are not connected correctly.

Rules are rules, and if the pump is good and the parts are good, then you will develop pressure.

Leave the gage installed, as it is a valuable tool for trouble shooting, and useful for monitoring the hyd system.

This is a very simple system and the value is under the jeep bed. So the Tee is between the high side of the pump and about a foot short of the inlet side of the control valve where it fits/can be seen. So I can't leave it in place. The gauge may not be working. I purchased it from Northtool and it was inexpensive.

I cycled the lift several times with no load and even when it was completely extended, I didn't hear any change in engine speed. So I'm not sure the valve is working correctly. It is a very simple affair but I don't know of a modern replacement. Since this is an antique, meant for show, I'd be happy if I can just lift the plow. After the show season, I might drop the lift and see if I can get the valve working.

triptester said:
Normally the reservoir should be vented.

The lift is installed according to these instructions from 1947 - Farm Jeep -Newgren Installation Instructions

There is no vent, but wonder if I can make vent by extending the fill tube (see here http://farmjeep.com/img/newgren_instructions/diagram4.jpg)?

Thanks for all the help.

medic0648 · Apr 30, 2013

If you can take the line from the pump to the valve loose and run it to the tank if possible and start the jeep. See if you even have flow from the pump.

lhfarm · Apr 30, 2013

medic0648 said:
If you can take the line from the pump to the valve loose and run it to the tank if possible and start the jeep. See if you even have flow from the pump.

I tested the pump for flow before I hooked it up to the lift tank. There is flow. Also, the lift does move up and down, but doesn't have a lift power. It will lift 200 lb, but not twice that.

Thanks,

medic0648 · Apr 30, 2013

Will it hold the load in the air? If it won't it may either be the seal in the cylinder or the valve leaking internally.

lhfarm · Apr 30, 2013

Yes, it will hold the load in the air, without a problem. This is a single action cylinder that does have a vent from the bottom of the cylinder to the tank.

medic0648 · Apr 30, 2013

Was asking to verify the cylinder and valve weren't leaking down. Sounds like either an internal bypass in the valve not allowing sufficient pressure or the pump is worn.

lhfarm · May 1, 2013

medic0648 said:
Was asking to verify the cylinder and valve weren't leaking down. Sounds like either an internal bypass in the valve not allowing sufficient pressure or the pump is worn.

The first pump I found was worn out and couldn't be rebuilt. The current pump is off an IH C that was being parted out, so it may well be worn too. This was the same pump used by Newgren. I don't know of a source for a new or rebuilt pump. The cylinder was completely rebuilt and is the only part I'm sure is working. The installation document on our Web site is the only document I've ever seen on the lift.

There is one clue in the installation document - "No adjustment on valve is necessary as this has been set at the factory." I'm going to dig up some photos of when I had the valve apart for cleaning to see if I can figure out what can/is being adjusted.

Thanks,

medic0648 · May 1, 2013

Do you have a hydraulic shop near you that could test it for flow and pressure? If not and you have a log splitter or tractor with oc hyd and a scv(or know someone that does) you could make a temporary adapter and try that. It would eliminate the valves being bad.

J_J · May 1, 2013

Was your vavle designed for your particular operation?

The relief valve could be set for a specific operation, but is it what you need. for the weight you want to lift?

Are you using your PS pump for the hyd, or is there another hyd pump just for the lift.

lhfarm · May 1, 2013

J_J said:
Was your vavle designed for your particular operation?

The relief valve could be set for a specific operation, but is it what you need. for the weight you want to lift?

Are you using your PS pump for the hyd, or is there another hyd pump just for the lift.

The crankshaft driven pump was what came with the original lift kit. The valve is original too. If you look at my avatar, that is the same lift installed on my 47 CJ2a. I was using a 12volt hydraulic pump at the time and it would lift implements with ease. When we (my son and I) decided to build a "show" jeep, we hunted and found (after about a 4 year search) an original bracket and pump (including the lovejoy). I immediately took the pump to a repair show and they determined that it was too worn to be used. So replaced it with an ebay IH C pump, which is the pump the manufacture used. Since I've had it working with an electric pump, I suspect the "new" pump may be worn to the point where it can't produce enough pressure. That would explain why I'm not getting much, if any reading on the gauge.

The only thing that makes me think there might be an issue with the valve was that it quit working 3 years ago, so I took it apart and cleaned it. But, most likely it is the pump.

I still have the electric pump and I could try to plumb it in and see what happens. Just not going to get that done before the show on Friday. At least I can show how the lift moves up an down and give small children a ride....

Thanks for all the help.

lhfarm · May 12, 2013

J_J said:
Are you sure you installed the gage in a tee in the IN port of the FEL valve?

Did you extend or retract any cyl to the max so the relief comes on.

If you have things connected correctly, you will show every psi the hyd system is developing.

If you did not see any pressure, then things are not connected correctly.

Rules are rules, and if the pump is good and the parts are good, then you will develop pressure.

Leave the gage installed, as it is a valuable tool for trouble shooting, and useful for monitoring the hyd system.

J J
I've been thinking about your note. While I'm sure the gauge is in front of the IN port of the FEL valve, I'm thinking the pump is running backwards. So things may not be connected correctly. The ports on the pump are the same size, only the manifold has different sized ports. That, in my mind, would explain the pressurized tank and NO reading on the gauge. I'm assuming the control valve could work, if not correctly, with things running backward.

Because of the mounting, it would be easier to reverse the manifold than try to rig up a way to test the flow direction. If I am wrong, and the pump is running correctly, could I do any damage by reversing they lines as a test?

Thanks for all the help.

J_J · May 12, 2013

Show us a picture of the valve.

The IN port is usually close to the relief valve.

The IN port is usually larger.

Some pumps can turn both CW, and CCW equally.

You can place the IN hose and OUT hose in two buckets with fluid , and see which port is the OUTPUT.

The pump should have an arrow or something to indicate direction.

If the ports are same size, the pump may be able to turn either direction.

This pump is reversible, and the ports are the same size.

http://www.surpluscenter.com/item.asp?item=9-10033&catname=hydraulic

lhfarm · May 12, 2013

Here is a string from when I rebuilt the valve a couple of years ago http://www.tractorbynet.com/forums/hydraulics/182148-need-help-rebuild-little-control.html

I actually did check the pump flow when I first mounted the pump and thought I had reversed the manifold. I may have to drain the system and try the buckets again.

Thanks,