Cat 317b lacks power

[Pralhad Birdi]

Pilot pressure at the pilot pressure port just about the pilot relief valve.

 

[Pralhad Birdi]

So bit of an update, excavator is still having the same issues.
Measured pump pressure, it’s within spec.
I’ve taken the entire control valve block apart twice, checked and adjusted all the relief valves twice, checked all the spools, and still no change.
Then I had a power loss issue on a 320D, and the monitor displayed a message saying “low mobility mode”. Turns out someone had flipped the auto/manual switch behind the right hand armrest to manual. When I flipped it back to auto, power was back to normal.
So I tried that on this excavator, but there’s no change. So I opened up the panel and measured all 6 wires with a voltmeter, and all of them are at 0V.
Does anyone know whether this would cause the issue?

Cheers guys

 

[rmllarue91]

Sounds like computer doesn't have control of prv valve but it's more than that if it doesn't work in manual mode. Manual mode Should send steady power to prv so machine can be operational not as fast as normal but useable

 

[Pralhad Birdi]

So it’s got a manual throttle control on it, so when we rev up higher, it does have enough power to do a reasonable amount of work. But after a while, say half an hour, it loses power, and you need to increase the throttle further to get consistent power output.
I’ve measured pump pressure once it loses power, and it’s still the same as it was on start up.

 

[rmllarue91]

Pump pressure is how big of a rock you can move. pump flow or volume is how fast you move it. Flow of pumps should decrease as engine feels a load. The prv valve is controlled by computer and it when working properly changes pilot oil pressure going to pump regulators to destroke pumps. In service manual there's theory and operation section which would explain it better. Get a book or download one. Understand the theory then test valve and report back.

 

[anuradha]

Hi,

Did you check the pilot pump delivery pressure at the pilot manifold pressure port near the pilot relief valve ?

If you didn't check, place the machine on to power mode 3 using monitor pannel power mode selection button and place the engine speed dial to position 10. Turn OFF the AEC switch from the monitor pannel. Bring the hydraulic oil temperature to 50 - 60 celcius by stalling implements several times.

Now check the pilot pump delivery pressure at the pilot manifold pressure port. It should be 500 ± 30 psi.

As you said, if the power looses after working some time then check the pilot pump pressure at that time also as i mentioned above. Because sometimes if the pilot pump is bad it will looses its delivery pressure when temperature raises.

 

[Pralhad Birdi]

Pump pressure is how big of a rock you can move. pump flow or volume is how fast you move it. Flow of pumps should decrease as engine feels a load. The prv valve is controlled by computer and it when working properly changes pilot oil pressure going to pump regulators to destroke pumps. In service manual there's theory and operation section which would explain it better. Get a book or download one. Understand the theory then test valve and report back.

Makes sense. Any chance anyone would have a copy of the relevant pages in the manual?

 

[Pralhad Birdi]

Hi,

Did you check the pilot pump delivery pressure at the pilot manifold pressure port near the pilot relief valve ?

If you didn't check, place the machine on to power mode 3 using monitor pannel power mode selection button and place the engine speed dial to position 10. Turn OFF the AEC switch from the monitor pannel. Bring the hydraulic oil temperature to 50 - 60 celcius by stalling implements several times.

Now check the pilot pump delivery pressure at the pilot manifold pressure port. It should be 500 ± 30 psi.

As you said, if the power looses after working some time then check the pilot pump pressure at that time also as i mentioned above. Because sometimes if the pilot pump is bad it will looses its delivery pressure when temperature raises.

Thanks, I’ll check that and revert.

 

[Pralhad Birdi]

Also, is there any chance anyone would have some diagrams of the relief valves, and their specific components? I feel like someone has taken these apart before me, and fiddled with them, and I think they might be missing either some seals or some circlips. I’ve tried to get blown up pictures on the internet, but no success so far.

 

[thepumpguysc]

Seems like an awful lotta work when u can bump the throttle and “fix” the problem..lol

 

[Pralhad Birdi]

Seems like an awful lotta work when u can bump the throttle and “fix” the problem..lol

That’s certainly true. The only issue is that as the machine carries on working, we have to bump up the throttle more and more to get a consistent power output. So I’m worried about engine/pump wear from running at very high rpms for extended periods.

 

[Pralhad Birdi]

I’ve also been considering something else. I’m running several much older machines on a daily basis, like Cat 12F graders, Champion D-740 graders, Cat 955Ls, an IH TD14A…all purely mechanical. Would it then be feasible to just eliminate the whole PRV system and just run it purely mechanically? Or is it even possible/does it make any sense?

 

[rmllarue91]

My dad years ago made a plate with a bolt for adjustment to set pump control on a 320 that ECM was bad and customer was tight on funds. It was sort of slow but kept rpms up.

 

[Pralhad Birdi]

My dad years ago made a plate with a bolt for adjustment to set pump control on a 320 that ECM was bad and customer was tight on funds. It was sort of slow but kept rpms up.

Absolutely brilliant. So that would go on in place of the PRV solenoid? And would tightening the bolt increase or decrease main pump pressure?

 

[Pralhad Birdi]

Hi,

Did you check the pilot pump delivery pressure at the pilot manifold pressure port near the pilot relief valve ?

If you didn't check, place the machine on to power mode 3 using monitor pannel power mode selection button and place the engine speed dial to position 10. Turn OFF the AEC switch from the monitor pannel. Bring the hydraulic oil temperature to 50 - 60 celcius by stalling implements several times.

Now check the pilot pump delivery pressure at the pilot manifold pressure port. It should be 500 ± 30 psi.

As you said, if the power looses after working some time then check the pilot pump pressure at that time also as i mentioned above. Because sometimes if the pilot pump is bad it will looses its delivery pressure when temperature raises.

I’ve checked the pilot pump pressure, and it’s about 250psi at high idle. Does this indicate an issue with the charge pump?

 

[Pralhad Birdi]

I’ve tried adjusting the pilot relief valve, but there’s no difference in pressure even if I screw it all the way in.

 

[anuradha]

I’ve checked the pilot pump pressure, and it’s about 250psi at high idle. Does this indicate an issue with the charge pump?

Hi,

That means it doesn't have enough pilot pump delivery pressure. It may be the cause of your problem.

 

[anuradha]

I’ve tried adjusting the pilot relief valve, but there’s no difference in pressure even if I screw it all the way in.

If you can, remove the pilot pump relief valve and disassemble it and see wheather is it good in condition. If the pilot relief valve is faulty or debries stuck in it, then sometimes it will open before the system pressure rises to its intended pressure limit.

 

[Pralhad Birdi]

If you can, remove the pilot pump relief valve and disassemble it and see wheather is it good in condition. If the pilot relief valve is faulty or debries stuck in it, then sometimes it will open before the system pressure rises to its intended pressure limit.

I disassembled the valve, but couldn’t find anything especially untoward. Would you have an exploded view of the same, just so I can check all the components are there and arranged properly?

 

[Pralhad Birdi]

Disassembled the pilot pump, and the top plate on the driven gear side is completely worn (nearly 0.2mm). So currently trying to source a replacement plate or pump.