cat 312b excavator

[duckslayingpro]

Im working on a cat 312b. A guy was working it shut it off for the day got back the next morning started it to go to work and has no hydraulic power of any kind for the boom or tracks. I checked to make sure the handle inside cab was making connection with multi-meter had good voltage so getting connection there. I think I think i have it narrowed  down to the hydraulic lock solenoid. But is there anyway to test this solenoid before I order a new one. Thanks for any help.

[giant splinter]

Duck,
When you say you checked the handle inside the cab .... are you referencing the "hydraulic lockout control lever" on the left side of the operators seat front of the console?. Also check the pattern changer to see that it is not in between system patterns rather than fully engaged in any one of the modes of operation, they can get bumped out of positive engagement by things like thermoses or grease guns by accident, is the operator using a modified ground disconnect key? (filed down so that it can be removed) leaving the ground circuits engaged w/o the key in place. Inspect the hydraulic pump area to see that nothing changed over the course of the evening such as a rat chewing on a tasty wire.You can call Caterpillar for help trouble shooting the problem also. I hope this helps.

[duckslayingpro]

Yes that is the handle im talking about. Im not sure on the other questions you asked. I will check those. Thanks for the reply.

[240b]

I owned a 311 had wire harness pinched under cab one day. crushed wire.    also pressure switch up on valve body for track over boom function were common on older models.

[duckslayingpro]

Well Ive found the issue to be wires chewed in two under the cab by a rat or rats. I could not beleive all the rat feces and huge nest on both skid plates under the cab. I was able to get some of the wires reconnected. I now will have to spin the cab to get to the others or jack it up? My question is will it hurt anything to spin the cab with a skidder since I have no hydralic power to turn the cab?

[giant splinter]

The swing cycle has a bypass valve, its not the best thing to force it through the bypass cycle but you could do it in a pinch ..... see if you can get current to the valve body electrical side first in your effort to rotate the cab if you have the service manuals it will show you how to engage the bypass without forcing it, you can also undo the hydraulic lines and couple them together with a fitting and rotate the cab on the undercarriage but you will lose some oil in the process and it must be totally cleaned up or you run the chance of a fire in the engine/hydraulic compartments ( risky method ).
I am not sure if the control bank is direct flow actuated or electronic power assist on the 312B excavator .... look that up and if its direct you can bungee the swing lever off in the direction of desired rotation and it will be better than forcing the swing motors (rotary actuators) in this case.
If you cannot get any of those things to work try prying on the valves them selves to get the oil to move for you making it easier on the hydraulic system. Last resort get the skidder and yard it to where you need it be positioned to get the wires fixed and hope a seal or one of the relief valves stays happy ... if the swing hydraulics are weak or leaking off internally you will need to deal with that later. I hope you get it going soon and back to work.