I live in the Bahamas and have a 416 Cat back hoe that I am having issues with the swing and the steering neither one will come up to there required pressures on the end of there stroke and there very slow! I rebuilt both swing cylinder's today and it made no difference. can't get over 500 psi to the left and 1000 to the right unless I slightly pull back on the boom up lever it swings fast and at the end of the stroke it goes in to relief of 2350. any one have any ideas on what to do from here?? its not like I can call the local Cat mechanic, been doing my own mechanical work for 40 years but was pretty much a Ford guy and this one has me stumped. every thing else works fine except the steering and swing any one know were I can go from here, been reading up a little bit about how the hydraulics work and kind of points to a resolver valve problem???
Yes it sounds like a resolver problem. The last working valve in the stack is usually the one causing the problem. Most likely a secondary resolver leaking
i would like to know how this goes for you keep us updated. my 426 swings right just fine but when I swing left it will go nowhere until I pull up just a little bit on the boom. I think the resolver sends the signal to the pump to put out pressure/flow so it would make sense that the spool is shifted but the pump is not making any flow until the resolver sends the signal. that guy I bought it from said at one point the machine wouldn't roll over to start. of course he replace the battery and the starter and it still wouldn't turn. he discovered a stuck resolver sending signal to the pump locking the pump. the starter was not strong enough to turn the engine with the pump engaged.
Gus, watch out for a stuck control holding a spool slightly out of the hold position. This will cause the pump to put out too much flow and build heat. I think your slow swing is from dirt under a resolver ball allowing signal to leak off. Later Bob
I think I posted a diagram of the backhoe resolver network once before. Let me see if I can find it.......try this The circuits are as follows: - A) RH Stabilizer circuit. B) LH Stabilizer circuit. C) Boom circuit. D) Swing circuit. E) Bucket circuit. F) Stick circuit. G) Lift circuit. H) Tilt circuit. J) Steering circuit. K) Feed to pump compensator.
thanks for the drawing that helps, can you tell me how the pump flows? I understand it is a variable flow pump and it zero's out when it is not being used which is supposed to save on fuel and build less heat but what makes the swash plate move and the pump start delivering? again thanks I appreciate all the help.
If you want the complete document that the above diagram came from which includes a full explanation of how the system works (including the pump) just drop me a PM with your email address and the Serial Number of your loader.
Gus, the signal that the resolver network captures from the circuit you want to use is sent to the pump control. This causes the pump to up stroke until the demand flow is met and the out put pressure is equal to the signal plus margin pressure. I think if you replace the seals on the resolver unit of the swing control you will have it fixed. Remove lower cap of control spool and take out plug with blade screwdriver. Later Bob