Bad pressure gauge?

[ning]

I set up a 5000psi pressure gauge with M&F connectors, stuck it on my backhoe loop, and operated a valve (briefly deadheading).
The dial didn't budge.
Fluid is definitely flowing through the line.

Bad gauge, or is this not a good place to put a gauge?

 

[ptsg]

Could you have, accidentally, put it on the return side?

 

[ning]

Could you have, accidentally, put it on the return side?

I can't assume anything today lol
I'll put it on both sides next time I have the backhoe on!

Question - what parts of the hydraulic system have pressure all the time?
I assume that there's pressure everywhere after the hydraulic pump; a line then goes to the steering, one to the loader valve block, one to the remotes, one to the backhoe? Or is the backhoe line somehow not pressurized without the backhoe actually being connected?

 

[ptsg]

With an open center hydraulic system just like yours, there is no pressure as long as all the valves are all in Neutral. There is a free path for oil to go back to the tank. Once you pull one lever and the cylinders start seeing some resistance, the pressure will start rising.

In this case, you want the gauge before the backhoe valve to get a read on the pressure of the backhoe. Ideally, you could also put the gauge right after the pump so you could check pressure on the loader, remotes, 3 pt and backhoe.

 

[ning]

With an open center hydraulic system just like yours, there is no pressure as long as all the valves are all in Neutral. There is a free path for oil to go back to the tank. Once you pull one lever and the cylinders start seeing some resistance, the pressure will start rising.

In this case, you want the gauge before the backhoe valve to get a read on the pressure of the backhoe. Ideally, you could also put the gauge right after the pump so you could check pressure on the loader, remotes, 3 pt and backhoe.

Ok. So if I wanted to check my pressure right now - with no backhoe on it - I can't just put the pressure gauge on the backhoe loop (without valves after it) and just operate eg a loader or remote valve, because there's essentially zero pressure unless you have a valve after the gauge?

I'm pretty sure my loader and remotes are 3/8", and this gauge loop is 1/2", so I'll have to wait till I have the backhoe back on the beast to check the pressure.

 

[ptsg]

Ok. So if I wanted to check my pressure right now - with no backhoe on it - I can't just put the pressure gauge on the backhoe loop (without valves after it) and just operate eg a loader or remote valve, because there's essentially zero pressure unless you have a valve after the gauge?

I'm pretty sure my loader and remotes are 3/8", and this gauge loop is 1/2", so I'll have to wait till I have the backhoe back on the beast to check the pressure.

Technically yes, if there wasn't another valve (3pt) in the circuit. So without the backhoe in the system, you have to connect the loop back together to feed the 3 pt and complete the circuit.

If you put the gauge right there in the loop, you should be able to see the pressure for the 3 pt valve. The way the 3 pt position control valve works always puts full pressure, regardless of the weight that is on the 3 pt. EDIT: When the 3 pt is being actuated.

 

[ning]

Technically yes, if there wasn't another valve (3pt) in the circuit. So without the backhoe in the system, you have to connect the loop back together to feed the 3 pt and complete the circuit.

If you put the gauge right there in the loop, you should be able to see the pressure for the 3 pt valve. The way the 3 pt position control valve works always puts full pressure, regardless of the weight that is on the 3 pt.

I thought that with the 3 pt just sitting in one place there's nothing impeding the flow, and unless you're raising or lowering the hitch, there's actually no flow to the valve - or maybe it's just in neutral - and so there's effectively no pressure backup from that valve? (kinda like the steering circuit, where unless you're turning the wheel this way or that, there's no flow to/from the steering valve)

 

[ptsg]

I thought that with the 3 pt just sitting in one place there's nothing impeding the flow, and unless you're raising or lowering the hitch, there's actually no flow to the valve - or maybe it's just in neutral - and so there's effectively no pressure backup from that valve? (kinda like the steering circuit, where unless you're turning the wheel this way or that, there's no flow to/from the steering valve)

Sorry, I meant " The way the 3 pt position control valve works always puts full pressure, regardless of the weight that is on the 3 pt." When the 3 pt is being actuated. Left that part out. My bad.

When the 3 pt reaches the preset height by the control lever, the flow that flows past the valve back to the tank/transmission with 0 pressure.

 

[Harry in Ky]

Sorry, I meant " The way the 3 pt position control valve works always puts full pressure, regardless of the weight that is on the 3 pt." When the 3 pt is being actuated. Left that part out. My bad.

When the 3 pt reaches the preset height by the control lever, the flow that flows past the valve back to the tank/transmission with 0 pressure.

I'm sorry but I have to disagree with your terminology on this one. While a do agree with everything you stated in regards to the gauge mounted in his "backhoe loop", unless you're talking about a tractor the likes of which I've never seen before, the "full pressure" you mentioned is losing me. I agree that the lift system (when activated) may get full flow from the pump until demand is met. Pressure, however, will only build to what is required to lift the load. With bare lift arms the required pressure would hardly register on a gauge mounted where his is located. With a heavy load on the three point, his gauge will read whatever it takes to lift it. Without that, his gauge mounted back there will won't tell him much about his system overall unless there is another valve between the gauge and the lift system he can deadhead to generate pressure. Unless that's the case here, I don't think he should be expecting to see much on his gauge.

 

[ptsg]

I'm sorry but I have to disagree with your terminology on this one. While a do agree with everything you stated in regards to the gauge mounted in his "backhoe loop", unless you're talking about a tractor the likes of which I've never seen before, the "full pressure" you mentioned is losing me. I agree that the lift system (when activated) may get full flow from the pump until demand is met. Pressure, however, will only build to what is required to lift the load. With bare lift arms the required pressure would hardly register on a gauge mounted where his is located. With a heavy load on the three point, his gauge will read whatever it takes to lift it. Without that, his gauge mounted back there will won't tell him much about his system overall unless there is another valve between the gauge and the lift system he can deadhead to generate pressure. Unless that's the case here, I don't think he should be expecting to see much on his gauge.

I understand what you say and I was actually surprised as well when I discovered it, although I haven't spent much time analyzing the circuit on the position control valve at the time. Anyway, I ran a pressure gauge on my tractor for quite some time. Right after the pump. Keep in mind all the 3 pt components on the OP's tractor are exactly the same as mine.

What I experienced is that every time I moved the 3 pt lever to lift the 3 pt, the pressure would go straight up to max pressure (2600 PSI), regardless if there was any weight on the 3 pt or not. As long as the 3 pt was raising, it was at max pressure, even if was just raising 1". I guess that's just the way the position control valve on these tractors work.

It's basically a closed center valve with an unloading valve.