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315C bogging down under load

Discussion in 'Excavators' started by masterwelder, Apr 18, 2020.

  1. masterwelder

    masterwelder Well-Known Member

    Joined:
    Jul 28, 2010
    Messages:
    113
    Location:
    NY
    CJC00776, 3046 engine, 6500 Hrs

    All hydraulic functions pull engine down. Worse when switch is flipped to manual mode. I calibrated throttle, changed fuel and air filters, checked screen at banjo fitting before lift pump (was clean), made a adapter that screws into bleeder port on filter housing to check fuel pressure. Pressure at idle- 18 psi, max rpm no load 14 psi, max rpm curling bucket or stick to dead head 7 psi. No smoke what so ever at anytime or throttle setting. Also did the same with a can of fuel as source run directly to lift pump. Got same results. I checked boost late last season and I believe it was around 9 to 12 psi full throttle while digging.
    I don’t believe it a HP problem but I’m unsure and can’t find anywhere a fuel pressure or boost pressure spec.
    Engine starts right up, never stalls, only thing that is a little unusual is a shaking/ vibrating on setting 3 and very slight in setting 4, all other settings run smooth.
    I do not have service manual yet- I’m looking, any suggestions on where to buy?
    I will be changing the pilot, case drain and hydraulic return filters this am. I have checked ground continuity to the hydraulic pump solenoids (good), power supply was 27 volts. There is a third electric 2 wire sensor with good ground and I got a 11.75 volt reading on that one.
    No active codes showing.
    I know where to go to do a prv calibration but I don’t know how to do it.
    Seams to track straight. There is a small bit of hydraulic fluid dripping out of bell housing (bad seal on input shaft?).
    I don’t have hydraulic gauges or flow meters yet- I’m pretty good mechanically and have read a lot of threads to get up to speed on basic hydraulic terminology and operation on an excavator.
    Can anyone walk me through the prv calibration? I would like to preform after I change filters.
    Can anyone speak to the fuel and boost readings for the 3046 engine?
    Any further suggestions and/ or comments on the fuel system or engine power?
     
  2. Nige

    Nige Senior Member

    Joined:
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    Location:
    G..G..G..Granville.........!! Fetch your cloth.
    A few snippets.......

    A service manual is Cat Publication RENR5520. They appear from time to time on eBay or other sites. Just to give you an idea a new paper one is $840, a CD version is $460.

    Fuel pressure should be between 11 and 25psi at full load engine speed. Your low values may well be related to the fact that the engine was at a significantly lower RPM than full load speed when you registered those values.

    I'll send you a copy of the procedure to check/adjust the prv and also an electrical schematic. Keep an eye on your PMs.
     
  3. masterwelder

    masterwelder Well-Known Member

    Joined:
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    Messages:
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    Location:
    NY
    Thank you Nige for the PM.
    I got the pilot, case drain and hydraulic return filters changed as well as tank screen cleaned. Started it up and rechecked fuel pressure, no load idle- 18, no load max throttle 14psi. I think fuel pressure is in range.
    Going to run it some today to see if filters and screen cleaning helped. Tank screen wasn’t plugged but had some fine particles. No brass, kinda like rust.
    I bought this machine from the original owner late last year, Story I got about it was it had sat for about 4 years after both back and front windows were knocked out due to one of his operators sliding into a tree. Was a rough time for him and he went out of business not long after.
    I brought it home straightened the cab up got the glass back in, changed oil, fuel and air filters, all belts, installed a hydraulic thumb and steam cleaned. Put about 60 hrs on before winter. Did a demo job and made some sand with my screener.
    My only issue has been the bogging down under load. Other than that it not to bad.
    Got to order gauges and fittings. Also going to change hydraulic oil.
    Can’t find the manual on Cat publications or in sis. Must be a call the dealer order only?
    Thanks again for your help.
     
    Last edited: Apr 19, 2020
  4. Nige

    Nige Senior Member

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    Cat Publications don’t sell service manuals. I’ve never quite figured out why.

    For a manual either search eBay or Google “servicemanualpro”. They sell genuine Cat manuals on paper & on CD.
     
  5. Cat_man320

    Cat_man320 Well-Known Member

    Joined:
    Nov 11, 2012
    Messages:
    172
    Location:
    Canada
    I had the same problem with my older 315l , I discovered a wire was off behind the seat in the cab , almost to the floor of the cab and bolted to the left hand arm rest housing , there is a little resistor there on mine and I must have knocked the wire off when i dropped a bottle of water when I was putting it back into compartment behind the seat . it made my pump go full output and would drag the engine down to a stop . Only found it accidentally after a week in the garage checking stuff out . your problem maybe be similar and something as simple as a wire broke or disconnected .
     
  6. Mbar

    Mbar Well-Known Member

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    Location:
    North Carolina
    Did you ever come to a conclusion on your issue. I have a 315c doing the same thing and have don’t even thing I can think of other than putting a flow meter in to check pumps
     
  7. Mbar

    Mbar Well-Known Member

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    Edit. Done instead of don’t.
     
  8. masterwelder

    masterwelder Well-Known Member

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    NY
    Not yet, but-

    Only used it for making topsoil so far this year and here’s what happens:

    Every time I disengage the safety lock And start to operate it is very sluggish and lugs the motor down. Shortly it will improve and run better with more power and will not lug engine down. It will continue to work as it should until either you engage safety lock or travel. Traveling the machine will lug the engine and other functions are week or not really at all. When you stop traveling and use the other functions it will bog the engine down and almost always will improve with in 30 seconds to a minute or so. Only a few times it lasted longer.

    It must be some gremlin somewhere. Electrical, hydraulically or ??? I’ve been through the fuel system completely.

    When it’s running good it seams to have good power, could be more but- as soon as you travel or lower the lock then re engage it starts all over with the lugging the engine and low power.
     
    Last edited: Aug 24, 2020
  9. JPV

    JPV Senior Member

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    Location:
    S.W. Washington
    Our CJC serial number 315 did something similar, however it was only half the functions that were weak. It turned out to be the spool in one pump controller that controls the swash plate had a "step" worn into it so it would hang up on occasion causing the pump to stay stroked even though the power shift pressure was right. It took some head scratching to figure it out. I took it apart and replaced the spool and that solved the problem for a while and then it did it again. That machine has the factory thumb that is fed from the main pump. When the thumb is activated it would slam the controller to full stroke instead of smoothly like when you are normally activating a hydraulic circuit. The long term fix was to install an orfice in the circuit to keep it from doing that although I don't remember where it went exactly.
    That doesn't sound like your problem exactly but it's something to think about.
     
  10. masterwelder

    masterwelder Well-Known Member

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    Location:
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    This machine has aux plumbing and has a third line for case drain. The previous owner did run a tamper with this excavator. I put a thumb on when I bought it, using it dose not seem to cause an issue but I do notice stick out really aggravates the problem along with the travel.
     
  11. masterwelder

    masterwelder Well-Known Member

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    I would like to check the spools in the pump controller. Where are they located and is it fairly simple to disassemble and inspect?
     
  12. masterwelder

    masterwelder Well-Known Member

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  13. heymccall

    heymccall Senior Member

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    All of my 314C,D, And E machines vibrate annoyingly until speed dial 4 or so.
    My 314C has the same 3046 engine. I dont like the fuel fressure at max rpm on yours.
    Debris gets trapped in the water separator/ screen assembly. The unit needs removed and daylighted (100% verified clean passages).
    With a 5/16" hose barb, you can bypass it, for testing.
    Also, if your 117-4089 separator element still has the water bowl on the bottom, it is not uncommon to lose, or omit, the bowl to element O-ring, and, since it is mounted higher, it may not leak, but, will most certainly suck air, if that ring is missing. Had that happen more often on my Deeres, but, really, it happens on most of the machines running a stanadyne separator. I know better, but, it's hard to get good help.
    Myself, I'd bypass it first and see if there is an improvement.
     
    JPV likes this.
  14. JPV

    JPV Senior Member

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    The spools are in the pump controllers which are bolted to both sides of the pump. It isn't too bad to get them off, all you really need are orings. As long as you don't mess with the pressure relief valve settings you can't really hurt anything in there as long as everything is kept clean.
    However after re-reading the thread I doubt that is the problem, the problem should only be half the functions or one track. It also seems like it should come and go more if it was the controller. For it to do it only when you travel or release the lock and then clear up doesn't make sense to me.
     
  15. masterwelder

    masterwelder Well-Known Member

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    Ok, back at it. I now have the full service manual.

    Hooked up gauges and did the sweep and calibrated prv. No improvement.

    My pump closest to the counter weight, cat calls it the right pump, has an output at idle of around 870# and the left pump 580#. At setting 5 with stick deadheaded both pumps are at 4750.

    The problems I can see with the gauges hooked up is obviously my right pump At idle has a greater output then the left, also when just barely moving the joystick for a function that use the right pump the pump spools up to max output, there is no modulation just goes right to max output. The pump will destroke some once you get past a fine control input, but when you initiate and want a fine movement the pump goes straight to full output.

    The stick function initially strokes the left pump, witch will stroke pump as needed. As demand increases on the stick it brings in the right pump to assist, the right pump goes straight to max pump output. It fights with the modulating left pump and loads the motor. When you get to dead head both pumps go to max output and really load the motor. Boom acts the same way as it uses both pumps. Bucket uses right pump and during fine operation the pump acts the same, goes right to max output. Swing is on left pump and works good.

    The right track, as soon as the track begins to move, will spool the pump to max output. The machine will not track straight. If you push the right travel lever all the way the pump will not be at full stroke and modulate some. The left track operates very smooth, modulates through the entire movement of the lever. When you try to track the machine slowly with the left pump modulating and the right pump at full output it tracks terrible. Even with both levers pushed fully one way or the other, the right pump is some what erratic and will not track straight.

    Power shift pressure appears to react appropriately at all time except while in settings 9 and 10. When in those settings, after stopping any function, the power shift pressure will not return to 425#, it will stay at around 175# and the automatic engine control will not reduce engine power. The pumps do destroke though. I would assume negative control pressure destroke the pumps? If you reduce the dial setting to 8 or lower the PS pressure will return to 425# and the AEC will idle the engine down again.

    So to sum up any function that uses the right pump, when a fine control or slowly pushing the lever causes the pump to immediately stroke up to max output. As you push the lever more the pump will destroke and modulate but the more you try to have fine control the pump is at max output and has no modulation.

    I did order tees to tap into the negative control lines but I got the wrong size, so at the moment I can’t tell what the signal to the pumps are at when at no load.

    I’m initially thinking my pump control for the right pump is malfunctioning. I suppose the difference in pump pressure at idle no load could be a nc issue. The other issues I don’t think could be related to nc though.

    Thoughts?
     
    Last edited: Dec 26, 2020
  16. masterwelder

    masterwelder Well-Known Member

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    Also there are no codes and the light is green on the controller.
     
  17. Mobiltech

    Mobiltech Senior Member

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    Sounds like your on the right track with the right pump control head being a problem. I think you will find a spool sticking or spring broken in that pump head.
     
    JPV likes this.
  18. JPV

    JPV Senior Member

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    I agree, take it off and pull it apart, I might have been right all along!
     
  19. masterwelder

    masterwelder Well-Known Member

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    Thank you. Will do.

    The manual says to drop the hydraulic oil. Do you think that is necessary?
     
  20. JPV

    JPV Senior Member

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    Yes unless you can put a good vacuum on the tank and leave it sucking as long as you have the controller off. I don't think there is a good way to plug off the pump when the controller is off.