I’ve been trying to set the relief pressure for my thumb on my Volvo 240b excavator. No matter how I adjust the two stage relief I can’t get the pressure over 1000psi and it will not hold any pressure after I let off the button. I don’t know if I have a broken part or am missing something.Anyhelp would be greatly appreciated! Thanks
Lets close the valves at the end of the stick. Check your pressure open and close. What fo you have?
On many of my older machines, the auxiliary plumbing has manual valve that when turned one way, allows oil from the control valve up one side, and allows oil down the other side into the tank. When the valve is turned the other way, oil can go up one line from the control valve and down the other side back to the control valve. Could you have said valve that needs turned, or, an electric controlled valve (if newer)? Typically, it's labeled as a one way/ two way valve.
I’ve been checking my pressures at the red arrow with the thumb completely disconnected so if I shut the valve off I would have no pressure at all correct?
This excavator has a two way toggle switch to go from hammer to shear mode and from what I’m told to operate a thumb you need it in shear mode which I think controls that two way valve
Yes, shear mode for hydraulic thumb. I wrongly assumed you had gauges on the pump. We need to know if its an attachment problem or a relief problem. Gauges should be on the pump test ports. Stick valves should be closed 100%. If you don't have the adapters to gauge the pump, stay where you are. Just cap the hoses going to the thumb, like you did. Open the valve all the way. The line should be the direction of flow. You're nearly closed right now.
Okay I don’t think I have the connections to go directly to the pump, I went to that connection I was previously at , opened the valve all the way and still had the same issue. Also the thumb was completely disconnected.
Same pressure in each direction?
I should’ve given you more information from the start sorry. I got the right side of the stick set too 2500psi by setting it with the backside valve.I ran into trouble after that when I started trying to set the left side. So currently the right side is at 2500 the left goes to 1000 and weeps pressure very quickly.
So the single stage relief is set at 2500 and the 2 stage is struggling to reach 1k? Is that correct? Lets back up. How are you controlling the thumb function? Pedal, joystick or both? Do you have a 3 way diverter at the foot of the R/S stick, or does the return oil go straight to the main control valve or does it go back to tank? Has this thumb worked on this machine before? If you could follow the return oil line down the R/S of the stick and boom and take a pic, that would be very helpful in figuring out what you have.
Yes that is correct. The thumb is brand new and this machine has never had one. I’m controlling the shear function with the joystick buttons. Also I do have the three way divider your talking about. I can get a picture of it in a couple minutes.
Do you have a foot pedal control or Is it strictly joystick?
It is strictly joystick I believe, the only pedals on the ground are for the forward and back
I’m not sure if this will be helpful or not but I’ll mention it anyway.This morning it’s rainy so I got curious and hooked the thumb up and actuated it. It opens snd closes fine it’s just a little slow on the close from the lack of pressure. Also the bucket can push it back effortlessly since the pressure bleeds off I figure. Not sure if that can rule anything out or not I just figured the more information the better. Thanks