Hello. A few weeks ago I purchased a Cat 320CL which is my first piece of heavy equipment. I used it for the first time today and the hydraulics seems weak. I can scoop a full load of dirt but it’s very slow. Same with raising the boom and loading a dump truck - very slow. It’s like the engine is on level 8 speed and the hydraulics are on 4. The engine doesn’t stall and otherwise the machine seems to run great. I tried to do some reading on the job site and I don’t believe the hydraulic pressure adjustable. Any ideas on where to start? I’ve owned mini excavators for several years but nothing this size so I apologize for this basic question Serial number PAB03299 Thanks
I made a video today. It was a little hard to hold the phone at the same time but there is barely enough power to dig a full scoop of dirt. If I hit a boulder digging with my cat 305.5 it would drag the mini - the 320cl didn’t move. It picks up a full scoop of dirt very slowly. The machine only has about 3600hrs on it
could be a range of issues. main culprit would be the pressure switches. you can try this first, open the right side armrest and switch to manual mode (display switches off I believe) and see if the machine is operating quicker. if it doesn't help the power of the machine I think the issue is a faulty main relief valve. there's a few things you an do to diagnose further and even fix it by tweaking the main relief valve. But better take it step by step as I think you have a easy fix for the issue. PM me if you need any diagrams etc
Thank you for the response. Unfortunately I scheduled field service with the local Caterpillar dealer and they were out this morning at 8am. After 2 hours of diagnosis they are claiming that the machine is operating normal ♂️. I believe they said the pump pressure was holding at around 5000psi. They claimed the PRV valve could be intermittently sticking - but nothing was done since they weren’t able to find anything obvious. I will run the machine a little more next week and circle back
So I reckon the problem is that the pumps are developing pressure but not flow, hence the reason its so slow. Depending if the entire system is slow or just some functions you can eliminate certain problems. In your case I think its the whole system that's slow? Main relief valve: usually when this gives up the machine ends up being slow as the flow just goes straight to the tank from the control valve, you could try adjusting it but just mark where it was originally if you don't have a pressure test gauge Faulty pump pressure sensor: one of the 2 or both pump high pressure sensors could be faulty If the pressure develops and then dies after a second or less could be faulty regulators, we have seen that a lot with the C/D range of Cats You can go into diagnostics from the monitor and eliminate a lot of the issues, even read the pressure signals etc. So better do that methodically and you can trace it to the fault. Let me know if you need the manuals or any help just PM me. The code for getting into the SERVICE MODE is FFF1 or FFF2. Good luck!
I just wanted to post an update in case others are having the same problem. Digger hunter has been helping me diagnose this issue and I think we have made some progress towards identifying the issue. The machine seems to be generating proper pressure as displayed in the service menu. At least the pressure switch thinks so On engine speed 9+ the machine runs perfect, it’s only in lower speeds the machine has very low power. The decrease in power is not lineal. On the 330cl at work and I’m my 305.5 I can do everything I need on level 6 or 7. On the 320cl it will hardly dig dirt on the same setting. I did discover that in manual mode the machine has noticeably more power so it was suspected that there is the issue with the PRV valve. The settings of the PRV valve were adjusted in the monitor to see if there were changes in performance. At +30 low and + 30 high the machine would barely move (as expected). At -30 / -30 it was a huge improvement. I am however surprised that the machine is not stalling at the maximum setting so I suspect there could be another issue I purchased some gauges to do some testing and will update soon.
I was able to hook up the pressure gauge today and double check pressures. The PRV valve seems to be working. I can see a real time change in the PRV low and high pressures when adjusting the calibration. I have confirmed with the gauge that the machine is generating ~5200 PSI of pressure - even in level 6 - so I'm assuming it's a flow issue. What controls the hydraulic flow of the machine in slower speed settings and how can I validate it's working correctly?
I believe it is possible to tune the pumps but its been such a long time since I've done it I couldn't possibly trust myself to give you the proper info. I seem to recall it involves setting the margin pressures using gauges and a flowmeter.
That’s actually helpful. Most likely the Caterpillar dealer will be returning to attempt to figure out what the issue is. I could suggest they look into it that
On Cat C series mid size excavators the hydraulic output of the pumps have a programmed output based on engine speed up to level 9 on the throttle dial. In throttle level 10 the hydraulic system is load sensing where the output of the pumps is matched to the RPM levels of the engine as the machine is operating. As I recall there is a process in the diagnostics of the onboard computer to calibrate the engine throttle control to the throttle dial and then another procedure to calibrate the PRV. I don't have enough experience on these machines to tell you how that is done but if you bring out the Cat people again, I would make sure to bring it up with them and then to stand there and make sure they actually do it.
John. I was able to calibrate the PRV but I was not aware of the throttle dial calibration. There definitely seems to be a flow issue. I was convinced it was the PRV but now I'm not so sure as it appears to be working. Pump pressure is good at any engine speed. Maybe the pump flow can be increased or maybe you are correct and a calibration will resolve the issue. I really need to get a service manual for this machine. Here is level 7 loading loose dirt....raising and swinging was at full speed.
The dealer is sending the tech back out on next Tuesday to diagnose the machine further. Based on comments above, I am going to ask the mobile repair tech to check/test the following: 1. Faulty Main relief valve 2. Faulty pump pressure sensor. (I just went to order one in an attempt to "throw some parts at it" and discovered they are $919 each) 3. "Tune" the pumps using a flow meter. 4. Calibrate the engine throttle control to the throttle dial 5. Pump Controller? This was a suggestion by an in house repair tech at the CAT dealer. The machine easily generates full pressure at lower RPMS so it seems like a flow issue. The PRV seems to be functioning. If there are any other issues which would cause significantly reduced flow at lower RPMS please let me know.
One thing I would check is the engine speed sensor that is screwed into the bell housing under the muffler. It can pick up metal filings off the ring gear and foul up the signal the computer needs to tune the pump to the motor to keep the motor running at a constant rpm. It will basically default to a low flow condition. Unscrew it, clean it, run it in until it touches the ring gear then back it out 5/8ths of a turn and try that. I have seen that be the problem you describe before.
Thank you for the suggestion. That looks like something that would be easy to check - I’m on it.
After thinking about it that could only affect it when the throttle is at 10. I don't know if it affects it at lower throttle settings. Will be curious to hear.
To clarify, the speed sensor issue will be easily confirmed both in the diagnostic codes and a 0 form engine speed in the diagnostic screen in the monitor. If it is reading realistic RPM, it is probably fine. You need to run all your diagnostic codes. I suspect your "tech" is more or less a quack if he thinks that is 'normal'. Don't pay that bill! Your pumps are not up-stroking. If you are not familiar, the pumps are variable displacement and there is an electric servo that controls the swash plates thus the volume the pumps put out. You need to implore that your tech investigate servo positions and recalibrate if needed. What I suspect if they are not doing a damn thing so the only increase you might get is just the RPM bump. Basically running on idle flowrates, just with higher RPM.
Hey, Just make sure you check these out if the dealer is coming out. -Governor/stepper motor calibration (you can do this yourself pretty easy) from what you have already done this should be ok so just a check of the RPM from display monitor should suffice -Check Negative Control pressure from MCV to pump is ok, it should go to zero when you operate any implement fully. This is what increases pump stroke and there's one for each pump going from each half of the MCV. Would be interesting to see if the pressure is dropping but pumps flow is not increasing. We have seen SBS80 pumps with the regulator arm spinning back so could be that. However haven't see a SBS120 on a 320C do that yet! If its has gone back then the stroke angle would be reduced quite a lot and that could be a an issue. -Check current at PRV is within spec, should be between 0.1-1.0amps from idle to when pumps are being relieved Hopefully they sort you out this time!
From all your testing and the video I would doubt very much that it is a main relief problem. You say the pressure is good at all speeds so if it was a relief problem you should see a drop in pressure at low rpm. I would definitely be looking at negative flow control settings and also pump control head adjustments. I didn’t see any mention of pilot pressure testing at all rpms. That could also be an issue if it’s dropping off at lower rpm. I would also do a track speed test to see if both are equal to rule out one pump being weaker.
This is something I meant to mention and it should be checked! Weak pilot pressure will not allow main spools to move as they should even if you are applying full stick. What I would probably do is select one side of one spool on the main valve block, command that function with full stick, and verify full pilot pressure is there. Sort of checking the pump, relief, etc, all at the same time.
I was able to go into the diagnostic screen and I did see RPMS which looked realistic to me. There were no fault codes detected so maybe I'll suggest the speed sensor if the other items check out. Or maybe i'll just clean it myself while he's working on other things. Unfortunately the $1500 bill was paid. They took my credit card prior to coming. I basically paid $1500 for 3 hours of the tech checking pump pressures. He did fix the thumb at least I'm trying my best to keep up with you guys but I'm out of my comfort zone with heavy equipment repairs. I'm going to add your suggestion about the servo positions / calibrations and show this to the tech on Tuesday. I really appreciate the suggestion.
I'm not sure why the video was removed up top but here is a video of the machine at level 6 speed. It was hard to operate and film at the same time but hopefully you can see that the machine really struggled digging dirt. It's interesting you mention about the track test. I actually noticed when tracking the machine that it did have a slight pull to one side. I dismissed it as maybe uneven terrain but now I'm going to take a closer look at that. I'm going to revise the list based on your comments.
It's interesting you mention about the track test. I actually noticed when tracking the machine that it did have a slight pull to one side. I dismissed it as maybe uneven terrain but now I'm going to take a closer look at that. I'm not sure if it's related but the thumb does not hold pressure either. If I pick up a log or rock and try to walk with the machine it will drop it. If you think this is related please let me know - otherwise I'll save that issue for another day https://youtube.com/shorts/Z19EI7R1la0?feature=share https://www.youtube.com/shorts/Z19EI7R1la0
What does it do on level 10? What does it do in manual mode (under arm rest)? Does it ever track straight? Are all functions affected? You are going to need to document the when and what. I have ZERO faith in the dealers. I personally have a C because the owner was tired of wasting money with the dealer that could not fix the issue. In every single issue, they were minor and took me extremely little time to troubleshoot and repair. I think you will be MUCH better served with a REAL independent tech (like a few on here) that are better fixing than taking credit card numbers. The way this works is dealers hire people with little skill but they get some sort of "school certificate" that says they know stuff. They don't! The actual good ones eventually leave and do their own thing! Why? Because they can actually solve a problem and realize their worth! In the vid, you can clearly see a total lack of 'force' (maybe we can call it power, even thought that is a work rate over time, I digress), in which pump pressure would be largely suspect there and I would have it in diagnostic mode to see pump pressure during that test. The actual force in hydraulics cares zero about volume of flow, it cares about pressure. Your 'speed' is where the volume comes in. I highly doubt cleaning the speed sensor will do anything as it is being ignored I believe at lower engine levels anyway. The ECU would flag erratic behavior. ALSO-- you mentioned "he fixed the thumb at least". What did he 'fix'? That very well could be related.
On level 9+ the machine runs great. Tons of power. Its amazing how big of a jump it is from level 8 to 9. Level 8 is very underwhelming - even for a 50k machine. I'm not sure if I posted this before but I picked up a very large rock and timed how fast it would lift the rock from the ground to the top of the tree line. This was done on level 7 and it was very sluggish. If I put the machine on level 7 and then flip the manual throttle switch under the arm wrest the machine is noticeably faster at the exact same RPM. I don't know enough about what that switch does, but I did read somewhere that in manual mode there are some electronic functions that are overridden. I hooked up a pressure gauge and the machine has no trouble making full pressure at a lower speed. The thing that is throwing me off the most is the PRV calibration. I hooked up a gauge and adjusted the values in the monitor so the LOW pressure was 72 and the HIGH pressure was 362 per the service manual. The machine was a dog. After reading a post from a few years back that said lowering the PRV pressures would increase the pump flow, I lowered the values until I eventually hit the maximum adjustment which was -30 and -30 High. The LOW pressure was so low it would barely register on the gauge. The machine ran 10x better - but it didn't help me solve the root cause of the problem. The thumb toggle switch was backwards. Down on the toggle raised the thumb while up on the toggle lowered the thumb. It was backwards from my other machine (and probably all machines) so it drove me crazy. It was like that when I purchased it.
You posted a vid about the thumb bleeding off after you clamped. Is that still happening? Ultimately, if you are seeing full pump pressure at lower engine speeds, yet arm force is pathetic, it is nearly a guarantee that flow or pressure is being lost somewhere. I could hear the machine bog a bit so it's doing something. If you were to put a pressure gauge on the 'stick-in' function, it is not likely to be anything close to system pressure. If you have a pattern changer on machine, ensure that is locked into a position and not slightly screwed up. That can really cause function issue. Also indicate if you have seen any cylinder drift on anything? put stick all the way out, does it stay there? Boom down and lift machine, does machine stay in the air?
Thank you to everyone. I really appreciate it. I updated the possible causes per your suggestions. 1. Negative flow control settings 2. Pump control head adjustments 3. Pilot pressure testing at all RPMs. Select one side of one spool on the main valve block, command that function with full stick, and verify full pilot pressure is there. 4. Check Negative Control pressure from MCV to pump. It should go to zero when you operate any implement fully. This is what increases pump stroke and there's one for each pump going from each half of the MCV. 5. Investigate electronic servo that controls the swash plates. Check positions and re-calibrate if needed. 6. Check current at PRV is within spec, should be between 0.1-1.0amps from idle to when pumps are being relieved 7. Governor/stepper motor calibration 8. Faulty pump pressure sensor. (I just went to order one in an attempt to "throw some parts at it" and discovered they are $919 each) 9. "Tune" the pumps using a flow meter. 10. Calibrate the engine throttle control to the throttle dial 11. Pump Controller? This was a suggestion by an in house repair tech at the CAT dealer. 12. A track speed test to see if both are equal to rule out one pump being weaker. Other: Speed sensor (possible but not likely) Faulty Main relief valve (possible but not likely)
Yes. The thumb is bleeding off pressure. I purchased the machine used a few months ago and I wasn't able to dig with it because it was in a parking lot. I used it for the first time and realized that it had very little digging power so I parked it and waited two weeks for the dealer to arrive. At the time I didn't know the thumb was bleeding pressure after being clamped so I didn't have them investigate. I haven't noticed any cylinder drift. In fact, one day I was doing testing with the gauge and had to leave abruptly. I left the arm in the air with the bucket about 4' off the ground. I returned a few days later and it was still in the same position. I have also used the boom to raise the tracks in an attempt the lubricate them (Some of the links are frozen due to sitting) and the machine did not drop. I hope this helps
Try running the machine with the throttle on 10 and see how it acts. Bad Bob
Hi Bob, The machine runs great at level 10. Tons of power. Anything under level 9 and it’s very slow.
Why u work under level 9 ?
Good point, the only time I run on anything but 10 is when I want it to be slow and sluggish, it might be normal.
It isn't normal. I run one and half the time I run less than WFO because I am the owner and paying the fuel bill.
The tech came out this morning. His plan was to separate the pumps from the sensors and do flow test. This would narrow down if the issue was with the pumps or an electrical component/other. Unfortunately during the test of pump 1, the hose started to leak. The first 25% that he completed was flowing a little bit more than spec. The tech did notice that the static pressure on pump one was around 500psi and pump 2 was 174psi. He was going to look into whether that was normal. With regards to the list: 1. Negative flow control settings 2. Pump control head adjustments 3. Pilot pressure testing at all RPMs. Select one side of one spool on the main valve block, command that function with full stick, and verify full pilot pressure is there. He said the pilot pressure was tested and was 600psi. 4. Check Negative Control pressure from MCV to pump. It should go to zero when you operate any implement fully. This is what increases pump stroke and there's one for each pump going from each half of the MCV. 5. Investigate electronic servo that controls the swash plates. Check positions and re-calibrate if needed. He said this is on the D model machines 6. Check current at PRV is within spec, should be between 0.1-1.0amps from idle to when pumps are being relieved. Done - everything checked out 7. Governor/stepper motor calibration Done. It was a little off but not bad 8. Faulty pump pressure sensor. (I just went to order one in an attempt to "throw some parts at it" and discovered they are $919 each) He seemed to think the pressure sensors were good. He had the pressure gauge hooked up and it matched the sensor readings on the monitor within 40psi 9. "Tune" the pumps using a flow meter. This is what he's looking at now. He noticed that the nuts to adjust the pumps had some paint missing and was suspicious that somebody has messed with them previously. 10. Calibrate the engine throttle control to the throttle dial Done. Duplicate of #7 11. Pump Controller? This was a suggestion by an in house repair tech at the CAT dealer. 12. A track speed test to see if both are equal to rule out one pump being weaker. I tracked the machine for several hundred feet yesterday and didn't notice a huge difference . It might have a little pull but its not like it was pulling heavily to one side.
MANUAL FLOW ADJUST turn IN the screw in the middle QUARTER TURN or 90 degrees clockwise of the regulators do this with the machine idling at about engine speed 3/4/5 attach the pressure gauge to each pump and turn in until you read about 40-50bar from teh MAIN PRESSURE port for the pump after doing that hold arm and boom in and the engine should smoke at relief a bit for a second or so and the PRV should then kick in and relief the pump if the engine stalls etc you have to then calibrate the PRV this is the only thing i can think of given the findings so far the issue is a lot of the diagnosis we do depends on the engine and hydraulic noises (belive it or not!) and usually just by the way it sounds we can kinda of guess where the problem is. But with your case the data is a just not adding up. from your videos, theres no way the cycle times are ok on that 320C. The reason I think you should do the above is that the P2 idle pressure seems a bit off. So try with P2 first NOTE original position of the screw so you can return it to where it was.
as I said teh above is a dirty fix last resort........but at your own risk so to speak and you really have to be careful you don't overdo it. Listen to the engine and you can just about hear it loading up a teeny bit and that's where you stop adjusting
and the pressure from our experience is around 40-50bar depending on wear of engine and pump.
The issue was finally resolved! There were a few issues.....the PRV calibration, the throttle calibration and the main culprit was low pump flow from pump #2. The flow test indicated that pump #1 was flowing about 10% above spec but pump 2 was flowing below spec. The adjuster screw for pump #2 was frozen so we were not able to increase the pressure and set it with the flow meter during the service visit. The PRV was calibrated and the machine was noticeably faster but still seemed a little sluggish. Throttle calibration was completed. I was finally able to free up the adjusting screw with PB blaster and a little heat yesterday. To be safe I turned the screw in 1/2 turn and it made such a huge difference. Its a totally different machine now. I spent $3500.00 in service so I'm not going to get them out again, but next time they come i'll have them tune the pump using the meter. For now, it's great Thank you everyone for commenting on the post. If "tuning the pumps" wasn't suggested, I guarantee they would not have been checked. And a special thanks to digger_hunter who called me several times (from Sri Lanka no less!) to help me with the machine. Everything you said was correct and I really appreciate it. You are a good man.
Nice! Glad its up and working again!
Glad it’s sorted!
New here as I just bought a new to me cat 320cl 2004 year model has 3750 hours in very good shape minus so dents and lights small maintenance things. The main issue was the throttle actuator was broken would start the trackhoe and it'd go wide open immediately and couldn't kill it with key or main power switch had turn fuel off. I replaced the throttle actuator with oem cat part but it's idled high prolly 2-3 guessing but is wide open on 10 in auto mode. My problem is in backup throttle mode you can idle the machine and it has way more power cause the machine want load up in auto mode just weak never pulls on pumps or anything rpm never changes. You put in backup mode it'll drag the machine or hit the tracks if don't let off the sticks so everything is working correctly there. My question is from reading your comments can I calibrate the throttle and pvc myself without having get cat to come do it? I'm wanting it to work the same in auto mode and auto idle down when stop for lil bit like it's supposed to. Backup mode is a beast but auto just want load up the pumps or have any power. I've serviced the machine and it tracks evenly and way faster in backup mode also cause it actually pulls on the pumps and bogs engine/ burns lot more fuel to Thanks guys appreciate any help with it.
Also my tracks have a fresh scratch on them on one side about half the track I assume that's from side loading to much weight and shouldn't do that? Was on a creek bank and noticed it end of day and tried not do it any more and seemed to help or not do it anymore.
The marks on the track pin bosses have two usual causes. The first is wear from the rock guard when the pad doesn't sit square on the ground. The second is a worn roller allowing the outside flange to ride on the boss. It is common practice to run the undercarriage till the chains and sprocket teeth are worn out and then just replace those items and not replace that bottom rollers or idlers.
Thanks John that would make sense I was setting on a pretty good slop digging from the side. Id say I wasn't very square cause haven't noticed it doing it again yet .