Cat 317b lacks power

[Pralhad Birdi]

Hi all,
I've recently had a Cat 317 Serial No. 4M00179 come back from a site where it was stood idle for a couple of years.
Upon testing, we found it was struggling to lift the boom and extend the stick under no load at engine idle. With increased revs, it would do it, but slower than it should.
We cleaned out the tank, fuel lines, replaced all the fuel filters, got the injector pump and nozzles serviced. Now the engine runs a lot smoother, but it's still got the same issues.
On idling, all the operations are extremely slow, and when you put the boom down, it just stops there rather than causing the engine to shut off. It's the same for all the controls. I'm pretty sure it's a hydraulic issue, but I'm not really sure where to start. Any ideas?

 

[rmllarue91]

Research prv in service manual

 

[John C.]

I believe the serial number is a 4MM0179 and is likely an A model machine.

 

[anuradha]

Hi,

As you explained I think your engine doesn't stall under load. Assuming that it seems to me that there is a problem of hydraulic flow. Lack of flow will slow down the speed of actuators.

If we think about the operation of PRV (Proportional Reducing Solenoide Valve ) it will direct the power shift pressure pilot oil to the pump regulators to destrok the pump according to the pwm signal sends from the controller according to the signals that it gathers from
1. Engine speed dial setting.
2. Engine speed sensor. &
3.Pump delivery pressure sensor.
And by this operation it will prevent the engine from stalling under loads.
If one of these components including PRV is faulty or its wiring circuits are faulty or controller it self is faulty, then engine will stall under load.
But I have an experience of over voltage supply to the PRV SOLENOID from the controller due to the problem of the controller and this will destroke the pump unnecessarily causing slow actuator movements.
So to check that we should check voltage signal to the PRV Solenoid without disconnecting it from the connector using a multi meter. To check this you will have to pierce the two wires if you don't have the check harness for that.
(Standard Voltage level should be
1-11Volts.) when machine runs and all control levers in neutral it should be 6-9 Volts. If the voltage level is much higher than this we can assume that there is a B+ short in the wiring harness or controller is faulty.

If the readings are normal then we can eliminate the above mentioned issue.

If the main pump has worn-out and if the internal leakages are more then also the flow will be reduced than the normal operation.

But before judging that I think there are several things to look at, things like whether the swash plate angle has been reduced by making adjustments from the Adjustment Screws & Etc.
I think members who has much more hydraulic knowledge than me will help you to figure this out.

 

[anuradha]

I believe the serial number is a 4MM0179 and is likely an A model machine.

Yes it is as he mentioned it should be a A model one with the above serial number.

If it is a A model then the voltage level for the PRV should be 6-6.8 Volts at high idle and all controls in neutral.

And

If you have a monitor panel switches like this
then press the power switch until power mode 3 indicator comes on,

If you have a monitor panel like this

then press the power switch until power mode 3 indicator comes on & Press work switch until it illuminates highest indicator lights other than the lowest indicator light and see the machine's operation whether there is an improvement.

 

[Pralhad Birdi]

My bad, the serial no. is 4MM00179.
I'll have a look at the PRV solenoid, thanks. Is that the one on the main pump?
Unfortunately the monitor display is completely wrecked, it's been that way since we imported the machine from Ireland.

 

[anuradha]

My bad, the serial no. is 4MM00179.
I'll have a look at the PRV solenoid, thanks. Is that the one on the main pump?
Unfortunately the monitor display is completely wrecked, it's been that way since we imported the machine from Ireland.

with this serial number it reveals that this is a 317 A model machine as sir John C said.
you can identify the prv location by reffering to attached image.

 

[Pralhad Birdi]

I've just tested the voltage at the PRV solenoid at high idle, and it's about 6-6.2V.
When the controls are being operated, at some points it drops down quite sharply, but always recovers to the same level.

 

[anuradha]

I've just tested the voltage at the PRV solenoid at high idle, and it's about 6-6.2V.
When the controls are being operated, at some points it drops down quite sharply, but always recovers to the same level.

It seems like supply voltage signal to PRV from the controller is good.
But to check whether it directs correct power shift pressure to the pump regulators, there is a test to do called as "PRV Sweep Test " . But to perform that you should use the monitor panel in order to access the data mode. As well as a pressure gauge & a multimeter is required.
As you mentioned if you can't use the monitor, measure the power shift pressure at the power shift pressure port at low idle & high idle.
And measure the pilot pressure as well at the pilot pressure port at low idle & high idle as well.
And put that results here, then someone will be able to comment on that.

 

[anuradha]

If you need these images will be helpful.

 

[Pralhad Birdi]

Thank you very much indeed, I'll measure the pressures as soon as I get into work tomorrow. Thanks again.

 

[Pralhad Birdi]

Would anyone have the hydraulic system T&A specs for this machine?
Thanks

 

[Nige]

You're lucky. It's an old-school machine where the T&A is all in one document instead of about a million separate ones which it would be for a newer machine.

 

[Pralhad Birdi]

Thanks Nige, much appreciated as always!

 

[Pralhad Birdi]

Finally got around to working on this excavator again.
Powershift pressure at tap 1 is about 20 bar. Pilot pressure at tap 25 is very low, again 20 bar. Adjusting the pilot relief valve both ways makes no difference to the pilot pressure.
Before doing this I tried changing out the hydraulic oil for heavier grade 68 to compensate for internal leaks/wear, but it made absolutely no difference. Machine still lacks any semblance of power.
Quite stumped at this point, so I'd be grateful for any advice.

 

[Pralhad Birdi]

Took out the PRV, because the solenoid itself seems to be working fine. Disassembled the valve, and saw the tiny spring at the bottom was completely collapsed. Replaced it with a similar diameter spring, but couldn't really tell the right length to cut it to as the original was completely gone. So I cut it to what I thought would be approximately the right length, put it back in and started up the machine. Pilot pressure went up to about 27 bar from 20 at high idle, and the machine had noticeably more power than before. Then I decided to take it out again, and slightly increase the length of the spring to give me what I thought would be more pilot pressure. On the contrary, pressure dropped back to 20 bar. Put the spring I had cut earlier back in, and again, pressure still at 20 bar. So I had it for a short period, but somehow messed it up. Anyone with any idea on where I could've gone wrong?

 

[anuradha]

Took out the PRV, because the solenoid itself seems to be working fine. Disassembled the valve, and saw the tiny spring at the bottom was completely collapsed. Replaced it with a similar diameter spring, but couldn't really tell the right length to cut it to as the original was completely gone. So I cut it to what I thought would be approximately the right length, put it back in and started up the machine. Pilot pressure went up to about 27 bar from 20 at high idle, and the machine had noticeably more power than before. Then I decided to take it out again, and slightly increase the length of the spring to give me what I thought would be more pilot pressure. On the contrary, pressure dropped back to 20 bar. Put the spring I had cut earlier back in, and again, pressure still at 20 bar. So I had it for a short period, but somehow messed it up. Anyone with any idea on where I could've gone wrong?

hi,

if you are able to perform the PRV Sweep Test then you will be able to find whether correct current signal comes to the PRV from the controller & also you can find whether PRV sends the correct PS Pressure to the regulators.

if the pilot pressure is below the spec of the pilot pump then first you should correct it before doing above mentioned test. a worn out pilot pump can decrease the pilot pressure and flow and it will reduce the speed and power of all the implements.

 

[Pralhad Birdi]

Thanks for the info!
What's the procedure for doing the sweep test?
Thanks

 

[Pralhad Birdi]

I removed the PRV today morning, cleaned it out and put it back. Bled out all the air from the system, and when I started the machine the pilot pressure was at 34bar at high idle. Tested it and the power was good.
Switched it off, started again a few minutes later, and no power again. Measured pilot pressure, it was down to 17bar at high idle.
Would this be a relief valve somewhere in the system sticking, or is it a sensor/solenoid issue?
Like I mentioned earlier, the cab monitor isn't working, so I can't really access any error codes on that.

 

[anuradha]

I removed the PRV today morning, cleaned it out and put it back. Bled out all the air from the system, and when I started the machine the pilot pressure was at 34bar at high idle. Tested it and the power was good.
Switched it off, started again a few minutes later, and no power again. Measured pilot pressure, it was down to 17bar at high idle.
Would this be a relief valve somewhere in the system sticking, or is it a sensor/solenoid issue?
Like I mentioned earlier, the cab monitor isn't working, so I can't really access any error codes on that.

What Do you mean here as pitot pressure ? Is it power shift pressure on power shift pressure port or pilot pump pressure at pilot pump pressure port ?