CAT 330LN Monitor and Controller error

[Liviu Popescu]

Small update - it seems that the stick and swings are slower than usual. However, if you move the boom whilst travelling forward, both tracks work (albeit slower) and the left one doesn't get stuck. I've read somewhere that when you are travelling straight and use other commands it switches both tracks on the upper pump so that it travels straight. I'm thinking now it might be the lower pump but when a pump goes bad doesn't it just stop working? Maybe it's something that de-strokes the pump. I'm starting to hope that the final drive is indeed bad because if it's something in the valve control/hydraulic, I know for a fact we will struggle a lot with the diagnostic... unless I get some fantastic help from this forum as usual

 

[John C.]

Have you pulled the case drain filter and hydraulic return filters and checked them for shiny things?

 

[Liviu Popescu]

John - can you tell me what/where the case drain is? in terms of filters e have identified three filters: 1 is the 4I-3948, the other one is 094-4412 in the hydraulic oil tank and there is also a 3rd one 108-8713 (also in the tank rom memory - this was very hard to find/order as it's not usually listed in the filter lists). Which one should we be checking?

 

[John C.]

I don't know the numbers that you are giving. The case drain filter is in the pump compartment usually mounted next to the hydraulic tank. The filters in the hydraulic tank are the return filters. Follow the hoses from the filter cartridges to where they go to. The third filter you are describing is likely a fuel filter.

 

[Liviu Popescu]

Hi all,

Small update - we had somebody in to look at the machine but there wasn't a great deal of success. They measured the inlet pressure on the pilot oil manifold and it measured around 35 bar (around 500 psi) which they said is within spec. They suggested that we focus our attention on the hydraulic accumulator which is mounted to the manifold but they didn't have equipment to measure it so we're on a bit of trial and error. From what I have seen, even if the hydraulic accumulator would be shot, I cannot find a logic why the right track works fine and the left one doesn't. Even if you run it individually (so you are removing the need for the accumulator to provide makeup oil) it still gets stuck.

I have attached a picture with what I am referring to, you can see the line they used to measure. They tried adjusting the pressure on the relief valve to 40bar just to see if it makes a difference but the valve screw snapped so we let it alone.

We did however solve some conflicting information and I can confirm without doubt that if you lift the track in the air then it will not get stuck.

Today we cut open the 2 filters. The hydraulic tank return filter is clean, however the pilot filter do have metal shavings - we think it's not that bad as they are quite fine and cannot see any copper particles but then again we are no experts - you might say it is a disaster. We are thinking that the machine is 29 years old however the pilot filter has less than 300 hours if that makes a difference (we changed some of the hydraulic oil in the winter, when we replaced the filter) but we couldn't do a proper flush of the system. Maybe these fragments were caught up in the old oil and have just recently been displaced.

Please see pictures of the two filters. Any suggestions would be more than helpful.

 

[John C.]

Lots of small particles in that last photo. 300 hours is not a lot of hours for the amount of metal on the paper.

The accumulator only allows you to lower equipment to the ground if the engine dies with it in the air.

 

[Liviu Popescu]

Thanks John - what would be the next step?

 

[John C.]

I don't remember if that machine has a separate pilot pump or not. If so, I would probably remove it and tear it down for inspection.

 

[Liviu Popescu]

Yes it does have a seprate one, however my judgement is currently excluding pilot pump issues as the right track and all other commands work.
I’m not saying the pump isn’t bad or worn, but wouldn’t it be more likely that this is a control issue? From what I’ve thought so far I can only think this is a control valve issue or a lower pump issue (that drives the left track) however the return filters were clean so I’m tending to exclude the lower pump?

 

[John C.]

I would suggest you put a gauge back into the pilot pump circuit and check the pressure as you are using multiple controls at the same time. If the pressure drops at all below the set pressure when not using anything, you have that as a problem. The description of your original issue sounds like a spool not operating as it should. A failing pilot pump putting debris into that system can make the pistons in the pilot control valve or the main control valve get sticky.

 

[Liviu Popescu]

Hi John, I told a lie, it’s not seprated per se, it’s within the main housing where the upper and lower pump are. Just for my knowledge, wouldn’t the pilot filter capture the debris anyway so the spools in control valves wouldn’t be contaminated?

 

[Nige]

Just for my knowledge, wouldn’t the pilot filter capture the debris anyway so the spools in control valves wouldn’t be contaminated?

That is a common misconception. The filter only traps what are commonly referred to as "dogs, tree branches, and small children." Not the smaller particles that can really do damage to valve spools (amongst others) in other words.

 

[John C.]

All filters have some kind of bypass function for when oil is cold. Start up after a cold night and maybe most of that oil is going around the filter.

 

[jrangel78]

solved the controller problem with programmed obsolescence camouflaged capacitors with a resistor inside... I attached images and if I could here the video of the machine operating at 100%

 

[digger_hunter]

Hi just saw your post. The issue IMO is that the pressure switch is not getting activated for the ECU to command the PVR or the PVR solenoid itself is stuck or inoperative. So try this. you can switch to manual mode by flicking the switch behind the armrest from auto to manual. Next you can set the pump flow to low or high using by flicking switch to tortoise or hare. you can then control the engine stepper motor manually flicking the up and down switch. if the hydraulics are quicker then you have a problem with the PVR part of the circuit.
to check the pressure switches (these are usually green or black 2 wire switches on the control valve). Unplug them and short out the two pins. You can just put a small sharp pin through the wires as well. this tricks the computer to think that pressure switches are activated so the PVR should open up and problem goes away. I think this model had pressure switches for each half of the main control valve. Try and let me know I can let you know next steps which would be to check the PVR and a a couple of other solenoids which control the travel speed etc.

 

[Liviu Popescu]

Hi all, they are going to look at the oil today hopefully - grasping straws a bit but if you look at min 2:52, when it swings left right, the track motor seems to want to move forward backwards. Could be nothing or something.

I've found an issue with this but it's unlikely this information that came out in 1994 is still applicable as it worked ok for 28 years. It's to do with negative flow control... which I don't particularly understand but am making an effort by reading as much as I can on it.

Hi all, will post a few updates as it’s been a long and painful and unsuccessful month so far with this. Keep things short, we have opened this valve section and found the sleeve to be broken in half. All other components looked ok. We bought just to be safe valve + springs + plunger + sleeve all new. Received everything except the valve today, changed the sleeve which was broken, swing and stick function better (the swing doesn’t get stuck anymore) but track issue is still there so I’m certain it’s not this that is causing this. We will put the new valve when it comes as well just to say we’ve completey done this change.

 

[Liviu Popescu]

Right, moving on from this CAT came to see the machine but didn’t really solve anything. Their work statement says:
- Checked pilot pressure from pedal and pump to control valve - all ok
- Checked left track plunger - all ok
- Checked implement and boom raise pressure sensor - both defective - we changed them
- recommended for us to check slow check valve - we’ve done this and it is ok

they did not have a flow meter only pressure gauges.

We’ve since change both pressure sensors (1 was genuine CAT and the other aftermarket) and there has not been any change to how the machine works, track still gets stuck. The AEC seems to be dropping the engine rpm correctly when pressed and no load and then as soon as you move something the engine accelerates - this was not working before.

Now - in practical terms:
- the left tracks works ok once in the air, as soon as it is on the ground it gets stuck as in the video. It works regardless of Power Mode
- swing does not get stuck anymore since we replaced the broken sleeve
- the excavator functions perfectly if the engine dial is on 7+, as soon as it is below 7 it gets stuck. It travels, loads, does everything as if there was no issue with it if rpm is above 7.

could it be the PRV valve? Negative flow control, pilot pressure, pump issues make no sense anymore if everyrhing is working when the rpm on the engine is high. Attached pictures of the two switches on the control valve block we changed (the green ones).

any suggestions please fell free

 

[digger_hunter]

Looks like your pressure relief valve for travel motor is busted. So it’s not building up pressure. You can stick a metal rod to jam the sprocket and run the motor with pressure gauge attached to see if the pump pressure hits I think around 4000psi. Gotta check the spec for that. But since you have looked at pretty much everything else it seems like a pressure relief valve faulty on the left final drive motor.

 

[digger_hunter]

If both pumps are hitting target pressure when arm is fully in and boom up both levers held to relief pressure with engine rpm at high then it would seem certainly like the travel motor pressure relief valve is busted. Could be just o rings are leaking on them so could be a cheap fix.

 

[Liviu Popescu]

Hi, the operator which went with the CAT guys said they measured the pressure at the travel motor and also on the pilot line. When the track gets stuck the main pressure drops to zero but the pilot pressure stays the same. He seems to remember that it was around 4000 psi before it gets stuck.
This is where he thinks CAT have measured the main pressure in the track motor. We have seen leaks there in the winter.

But if the pressure valve is busted why could it working for 2-3 seconds and then the track stops as per the video. Also what would be the connection with the engine dial above 7?