Randy,

The hydraulic pump has pressure relief valves inside the tank. They are adjustable. I lowered the settings of mine when I was testing my gear system for the first time (it just involves changing spring tension). You have to dissemble the pump at least a couple of times to get set them because you need to check the new setting each time.

My low-side relief setting is set to about 600 to 650 psi. I can raise the low-pressure-switch setting to above this value. The pump then runs continuously because the relief valve is open -- this is the check to verify the setting of the relief valve (you have to have gauges, of course).

Even with this low setting of the low-side relief valve, my low-side pressure still goes well above this sitting in the sun on a hot summer day. When the pressure increases slowly in this way, the valve just doesn't open at the same pressure as it does with the pump running.

I think it is best to set your relief valves as low as possible without having them open during normal operation.

Mike Reinath
LNC2 360 at 730 hrs TT
San Jose, CA (RHV)