Cat 330BL - Won’t rev up to take load

[Pralhad Birdi]

We managed to sort out the boom lift issue - turned out to be a loose spool
Tightened it up, and it lifts without drifting, and comes down slowly as it should.

We have however got a new and bigger problem now - operate for about half a minute, and it’s perfectly fine. Then, joystick controls become really stiff, and the machine loses all power and functions.

I feel like it’s creating too much pressure in the main valve. If I switch off, operate all joysticks to release pressure, and then start again, it’s okay for about 30 seconds, then same issue again.

 

[Pralhad Birdi]

Spent the entire day yesterday on this machine; did the following:
- Checked all the check valves on the main control valve
- Checked the slow release valve again
- Checked the filter bypass valve again
- Changed the o ring on the tank filler plug
- Tried bleeding out the main pumps as per spec, but I think my accumulator is discharged, so wouldn’t let me drop boom with machine off.

None of this made the slightest difference.

Right at the end, I decided to try and adjust the PRV pressure upwards and see if that helps (couldn’t tell which port you measure it at, so just played it by ear)
Took the screw in half a turn at a time, and controls improved, but would still become very stiff after one or two implement operations.
Took it in a total of 1.5 turns, and finally realised what the problem is - pumps won’t destroke after you release the joystick to neutral position, because the engine is still loaded up. Release the safety lever, and pump load immediately disappears. Re-engage, and it’s fine, operate any implement, moves like it should, with good speed and power, but release the joystick, and pump stays engaged.
Am I right in assuming this is an electrical issue, considering that releasing the safety lever destrokes the pump?

Additionally, checked the solenoid for the breaker pilot line - turns out pilot line was pressurised regardless of whether solenoid was energised or not.
Physically blocked the line at the solenoid with an aluminium rivet.

 

[Pralhad Birdi]

For anyone referring to this thread, here’s an update with where we’re at with this machine:
- Sorted out the PRV issue - turns out solenoid earthing was bad - now will destroke pump

Tested machine, operations were good for about 10 minutes or so, then oil temps would go up and same issue again.

- Adjusted the slow case drain valve out slightly, as I thought this might be causing a restriction in the flow.
- Found pilot pressure port on the pilot manifold, measured pilot pressure - 29 bar. Adjusted it up to 41 bar.

Tested machine, all functions seem good, but no power in the bucket now

Going to pull out spool to inspect

Then we can test the machine to see if the overheating issue still persists.

 

[pinhookfarm]

For anyone referring to this thread, here’s an update with where we’re at with this machine:
- Sorted out the PRV issue - turns out solenoid earthing was bad - now will destroke pump

Tested machine, operations were good for about 10 minutes or so, then oil temps would go up and same issue again.

- Adjusted the slow case drain valve out slightly, as I thought this might be causing a restriction in the flow.
- Found pilot pressure port on the pilot manifold, measured pilot pressure - 29 bar. Adjusted it up to 41 bar.

Tested machine, all functions seem good, but no power in the bucket now

Going to pull out spool to inspect

Then we can test the machine to see if the overheating issue still persists.

Did you ever figure out your overheating issue? I chased this problem for a long time last year and it turned out to be a broken slow return check valve. I did not end up reading your entire thread. So sorry if I missed it

 

[Pralhad Birdi]

Did you ever figure out your overheating issue? I chased this problem for a long time last year and it turned out to be a broken slow return check valve. I did not end up reading your entire thread. So sorry if I missed it

Figured it out to a certain extent, yes.
So the check return was part of the problem - one of my mechanics had over tightened it. Adjusted that back, and then the power shift pressures were out as well, and the PRV solenoid wasn’t working.
Really weird combination of issues that suddenly cropped up.
But since sorting all that out, it’s been working well - we’ve been cautious with it, giving it a few minutes idle time after every hour or so, but it is working.

Will probably pull the entire control valve block out when I get it back at the yard, and disassemble to inspect.

Thanks for sending the pictures of the valve, I’m intending to remove mine again as well and inspect.

 

[pinhookfarm]

Good deal! I am still chasing a issue with mine that I haven't had much luck. Been limping along as is, but going to get back into it. I changed the main pump and ever since the machine bogs down under load. Have rewired PRV harness because it was frayed. Replaced engine speed sensor because it was frayed. Have a good speed signal. In service mode 66 I can manually command the PRV with a high pressure and the pump destrokes and machine works well under load but obviously slow otherwise. But cant seem to find out why ecm won't command during normal operations. Posted in a different thread but not much luck.

 

[Pralhad Birdi]

Good deal! I am still chasing an issue with mine that I haven't had much luck. Been limping along as is, but going to get back into it. I changed the main pump and ever since the machine bogs down under load. Have rewired PRV harness because it was frayed. Replaced engine speed sensor because it was frayed. Have a good speed signal. In service mode 66 I can manually command the PRV with a high pressure and the pump destrokes and machine works well under load but obviously slow otherwise. But cant seem to find out why ecm won't command during normal operations. Posted in a different thread but not much luck.

So here’s a list of what I checked/did on my machine:
- PRV solenoid had bad earthing, redid that
- Pilot pressure was low, adjusted that
- Check return valve was in too tight, adjusted that
- Boom spool had randomly loosened itself so boom wouldn’t lift
- Powershift pressures were too low and too high respectively - set those
- My breaker solenoid was letting pilot fluid through without the pedal being pressed, so machine was always sensing a load, and pump wouldn’t destroke. Manually blocked off the pilot line.

Powershift pressure was what seemed to make a big difference for me. Maybe try increasing the lower one slightly higher than the reference value, so you’re stroking your pump less under load?

Also, I had a very similar bogging down issue on my 317B. Turned out to be pilot pump that had destroyed itself internally.

 

[pinhookfarm]

Hoping pilot pump is fine since it is in the brand new main pump. Ok thanks for that advice. I will investigate. Also the breaker solenoid is an interesting possibly. This machine was formally used for demo work and had a hard life I’m sure. I have deleted a couple of related aux piping because of leaks and other problems. I will update you if this leads me anywhere thanks!