Testing Haydraulic pump question.

Bean Juice · Feb 6, 2020

I want to test the hydraulic pumps on my kubota. I borrowed a hydraulic gauge that reads to 5K psi and it is tee'd with a flow control valve and line that can dump to a bucket or return to the fluid tank. I was going disconnect the output of the pump, plug the gauge directly into the pump and after starting the engine, slowly close the flow valve to let the pump build pressure. This way I can see if the pump will reach the recommended operating pressure for the system (~2100psi). Once I have made sure the pump is strong, I plane to test the pressure bypass valve and make sure it's set properly. My questions is; The gauge and hardware I have are 1/4" hoses and fittings. The pump lines on the tractor are 1/2". Is the difference in line size going to cause too much restriction to give me an accurate reading or cause other problems?

BertZegers · Feb 6, 2020

Why not test at the quick connect behind the pressure relief valve? If you find close to 2100 psi your done testing. Am I thinking to simple?
And why do you need to know?

Bean Juice · Feb 6, 2020

BertZegers said:
Why not test at the quick connect behind the pressure relief valve? If you find close to 2100 psi your done testing. Am I thinking to simple?
And why do you need to know?

The 3 point isn't working. The service manual says to start by checking the pump. There is no quick connect after the relief valve (too old?). You take the line out of the relief valve to the valve bodies off and put your gauge there to adjust the relief valve.

BertZegers · Feb 6, 2020

Bean Juice said:
The 3 point isn't working. The service manual says to start by checking the pump. There is no quick connect after the relief valve (too old?). You take the line out of the relief valve to the valve bodies off and put your gauge there to adjust the relief valve.

OK, in your first post you said to plug the gauge directly into the pump. If you test behind the relief valve, it should be safe for the pump. Could the relief valve be stuck open?

rScotty · Feb 6, 2020

Bean Juice said:
I want to test the hydraulic pumps on my kubota. I borrowed a hydraulic gauge that reads to 5K psi and it is tee'd with a flow control valve and line that can dump to a bucket or return to the fluid tank. I was going disconnect the output of the pump, plug the gauge directly into the pump and after starting the engine, slowly close the flow valve to let the pump build pressure. This way I can see if the pump will reach the recommended operating pressure for the system (~2100psi). Once I have made sure the pump is strong, I plane to test the pressure bypass valve and make sure it's set properly. My questions is; The gauge and hardware I have are 1/4" hoses and fittings. The pump lines on the tractor are 1/2". Is the difference in line size going to cause too much restriction to give me an accurate reading or cause other problems?

I understand that you plan to test for pressure by restricting the flow. That will work fine. The pressure will be the same everywhere regardless of the diameter of the line.
However.... for safety sake, you should put the bypass valve betwen the pump and the valve that closes the flow. That is what BertZegers is saying in message #2 and I agree. In that case, the pressure you will read will be the bypass pressure rather than the full pump pressure. But you don't care. If the pump will reach the recommended bypass pressure that's all you should ever have in the system. Hitting bypass pressure means the pump is working fine.

Diagnosing why the 3pt. is not working takes a little more effort. So check that the pump is putting out pressure first.
rScotty

oldnslo · Feb 7, 2020

Since you are attempting to run full pump flow through the 1/4 inch lines the size does matter.
For example: trying to run 15 GPM through 1/4 inch hose would have excessive pressure loss and depending on gauge location could give very inaccurate pressure reading vs what the pump is truly seeing

Is the pump exposed where you can touch it? If yes try raising the 3 point and see if the pump housing gets warm quickly compared to the inlet line. A pump slipping or leaking flow will get warm to hot quickly like in a couple of minutes.