My father in law has a 315bl that has been in a local shop for several months now. He was working a job when the hydraulic system stopped working. CAT diagnosed that the pump went bad so they replaced with a salvage and it didn’t work so he purchased a new one. Now that the new pump is on the hydraulic system is working: walk sweep boom and bucket all work. Unfortunately the hydraulic system is very slow and and won’t engage high flow regardless of engine speed. They received the hydraulic system schematic from CAT and we’re hoping to diagnose the issue this weekend. I have not worked on it yet and I’m providing what information my father in law told me so I apologize for incorrect verbiage and lack of detail. I am hoping to get some ideas on where we should start and what some potential problems could be. I am sure there is a laundry list of potential issues based on what little information I provided. I appreciate your input and look forward to hearing opinions. Luke
Serial number is needed. Also, how is auxiliary activated? Foot pedal?
Serial 3AW02141 No auxiliary hook ups on this machine. Pedals operate tracks and joysticks operate sweep, boom and bucket.
I'm not comprehending your fault. Everything works, but works slowly?
Yes that is correct. Its as if the hydraulic system is in limp mode. Everything works but all motions controlled by the hydraulic system are slow, and the speed/power of the hydraulic system does not fluctuate regardless of engine idle speed. CAT said the hydraulic system will be low flow until any of the hydraulics are engaged. As soon as you start using anything that runs off the hydraulic system it will automatically switch to high flow and everything will operate as it should.
Does the machine performance improve when in "override"? On my B machines, there were 2 toggle switches behind the RH armrest. The momentary, center off, is for engine speed once the toggle next to it is ON. Turning the other toggle ON results in a fixed powershift of the pumps.
Just to add a little clarification on how the machine and the pumps work. Your machine doesn't have a high flow / low flow system like a skid steer. It does have one pump flow and two pump flow. Your hydraulic valve is basically split in half with one pump feeding one half while the other pump feeds the other half. As I recall there are two spools in the machine for the boom and stick functions. One spool in each half of the valve bank. So when you boom up or stick out both spools are stroked and both pumps come on line. The bucket and swing functions only run off one spool or just one pump. Each track runs off one pump. When you are traveling and operate another function at the same time, like booming up and traveling, both pump flows will be joined together so that the travel and the rest of the functions will slow down some but still work and the machine will keep traveling straight. My impression is that for some reason one of the pumps is not being signaled to stroke up or there is a problem in the pump. The hydraulic operating system of the machine is what is known as open center / negative control. The negative control is basically a hose coming from the bottom of the hydraulic valve back to the pump. When nothing is being used the pressure will be somewhere around 300 to 500 PSI. When something is operated the pressure will drop and the pump will increase its output. Since you mention that it has a new hydraulic pump there is the possibility that maybe the NC hoses got swapped to the wrong pumps. You can tee in a gauge to each NC on the pump and watch the pressures when you operate something and note what happens. I'm sure there will be others come up with more possibilities. Have you checked the diagnostics in the monitor panel? Good Luck!
I will check this weekend when we go look at it. I am having trouble understanding what you are saying but as I said this is not my machine I dont know of the switches you speak of. I will bring it up to my father in law and see what he says. Thank you.
Maybe this will help. This is looking down on the back side of the RH armrest. (1) Backup switch (2) Speed change switch The electronic controller for the engine/hydraulic pump has a backup system in order to prevent uncontrolled operation of the pump and/or engine. When the backup switch (1) is placed in the manual position, the following conditions result: The proportional reducing valve is disconnected from the drive circuit of the proportional reducing valve. Then, the reducing valve is driven by a constant current that is adjusted by the backup resistor. The power shift pressure is kept constant and pump output is in the standard mode. The monitor does not display any information. The controller and the monitor are not receiving power. The engine speed can be controlled by the speed change switch (2). The engine speed will be increased, if the speed change switch is placed in the RABBIT position. The engine speed will be decreased, if the switch is placed in the TORTOISE position. The switch returns to the neutral position when the switch is released. The swing parking brake is released. However, the parking brake is engaged when the primary pilot pressure is reduced to near zero by placing the hydraulic activation control lever to the lock position or by stopping the engine.
Thank you for your response. As I said this is not my machine and I have not worked on it yet, just relaying info from my Father in Law. We are suppose to be doing pressure tests on everything this weekend. With that said my father in law mentioned that CAT said to check the two hoses going into the bottom of the hydraulic pump. If I am following correctly, these are the hoses you are talking about and that they may be on the wrong fittings. If I am following correctly and the hoses are indeed backwards (on the wrong pumps), the function you are trying to achieve (boom/bucket or tracts) its actually spooling up the opposite pump than what you are trying to use. For example, if you operate the hand controls it would spool up the pump for the tracks but when you operate the foot petals it would spool up the pump for the boom/bucket. Ultimately if the hoses are switched to the appropriate pump it would spool up correctly for the function you are trying to achieve. Am I tracking correctly or am I way off? I do apologize for my stupidity; I am just the middleman here.
My father in law stated that the speed at which hydraulic system operates does not change with the rabbit/tortoise switch. The engine will idle will change but the hydraulic system and functions are still slow.
HMC was referring to the backup switch #1 in the photo above that (when it's in the ON position) bypasses the electronic engine/pump controller and sets the pump at a fixed output. Thing of it as something akin to "Limp Mode" for the hydraulic system.
With that said he mentioned that he controls the engine idle from a knob and not these switches behind the armrest; he didnt even know they were there (I just called him). Is it a possibility that the backup switch accidentally got engaged into manual mode (while cleaning out trash or something behind the seat) and the hydraulic pumps are staying at a constant slow/low pressure?
So the speed switch (2) controls the speed/pressure of the hydraulic system only and not the engine idle?
Clarification: When the backup switch (1) is in manual mode.
It is a possibility that needs to be eliminated as part of the diagnostic process. What will also need to be eliminated is the possibility that a fault in the wiring is causing the backup function to be permanently activated irrespective of the switch position.
I looked into this switch a little more. As it says above, it will power off the monitor and it will prevent the throttle dial from working as well. He went and looked at it and said switch is not in manual mode, the monitor and throttle control still work. In reference to your electrical/wiring issue statement. Is it a possibility that if you switch into manual mode and control the throttle with speed switch that it may override any electrical fault in the system preventing the pumps from spooling up. As far as my father in law knows, none of the hoses are hooked up incorrectly. They used colored zip ties to note where the lines should go and that they were all matching. Still a possibility that they are incorrect but its starting to sound like an electrical issue to me but its hard to believe that it showed no signs of this until the original pump broke. Also, I found out that the original pump did not fail, the case for it actually broke. The salvage pump they put on worked but the same as what its doing now with the new pump; slow operation.
I don't think it is possible but I am not sufficiently familiar with the system to confirm that. Based on what you said above regarding the fact the problem was there even before chaging the pump it certainly sounds as though it could be an electronic problem. I will try to get hold of a copy of the System Operation and Test/Adjust manuals for the pump controller system and send them to you. Keep an eye on your PMs.
The electrical control system allows the machine to work at maximum engine capacity. Anything going wrong with the electrical system and you get less capacity out of the machine so the pump doesn't overload the engine. The bypass switch basically just shuts off most of the controls and applies a steady current to the solenoid that controls pump output. From past experience, the electrical system is probably not the source of your problem.
John, FWIW I agree with you. Don't you think it might be a good idea to eliminate the possibility of a problem in the electronic side as regards the pump controller before pressing on with testing the hydraulics.?
I do agree on checking he electrical system first because it is easy to do. I also have some experience with these machines in the past that tell me the problem likely is something internal to the hydraulic system.
Put machine into "override". Toggle engine to full speed. Operate machine. Is performance better than when not in override? Have you checked fault codes? Can your share them? The override puts the output at a fixed value...for argument, let's say 60%. If it ain't no better, the problem is probably mechanical. But, the fault codes need interpreted first.
Thank y’all. I will try and get fault codes and test with the bypass and report back.
@John C. - do you have an instructional video for the B-Series Monitor Panel.? I looked on your channel but didn't see one.
If I read correctly there was a major pump failure just before this issue. Do you know if repair shop did any cleaning of the hydraulic system or did they just throw a pump on and run with it. I have never personally seen a piston pump break a housing other than when there were hit by something. I would check electrical systems but would put money on the hydraulic system being full of shrapnel causing valves, regulators, etc to be sticking
I do not have all these detail. It could of possibly been hit. I’d hope they were smart enough to drain the system before throwing a new pump on and contaminating everything. I will find out and report back.
With a major component failure you have to do more than just drain fluid and change filters. Every single component is now contaminated and needs to be thoroughly cleaned. Find out what you can this weekend and report back and we will help you as best we can.
Exact words from my father in law, "it was knocking like a bad valve lifter then bang". Something inside the pump was failing, gave out and blew apart the housing. When they replaced the pump they drained all the fluids and changed the filter but that is all.
You may be in for a fairly large project
Here is a link to a video showing how to access the service menu in the Cat B series monitor panel. I didn't do this video but this guy does a good job.