safety suction valve, arm and boom check valve, Komatsu Pc220Lc-6L

[Jon_one]

Hello ,

I am a bit lost about some small issues i am having and the shop manual says it could be the check valves on the arm or bucket group . has anyone ever accessed these check valves with the control valve on the machine ? it seems impossible based on what i am seeing . i am hoping that i am wrong ..

What i also want to know is what is the procedure for adjusting the safety suction valves ? there seems to be some adjustment on some of them but i do not know what it does ? a longtime ago someone came and really messed up my machine and i think they interfered with that also. the shop manual has no information on adjusting this , they are the one that is labeled A

 

[mikebramel]

A should be your port relief. B should be the "suction" valve.
A controls the maximum pressure between the valve and cylinder/motor. B keeps the cylinder/motor from cavitating under gravity or when the opposite side port relief opens

 

[Hydraumind]

what are the symptoms that makes you think about port relief

 

[John C.]

Safety suction valves are all one piece. There can be individual safety valves and suction valves. The valves with no adjusters on them are not meant to be adjusted. Some of those are safety valves and some are suction valves. You have to have the right cartridge installed in the right port for proper operation of that function. You also have an arm regeneration valve mounted to the back of the main control valve block and an arm counterbalance valve that I never did figure out how to get to. I had plenty of trouble with those in the early years of that model machine. As I recall those port reliefs were set above the main relief on those machines. The one you had to watch out for was the arm port relief because on some ranges of excavators Komatsu set the port relief for arm out lower than the main. This I believe was in the mistaken belief that people would use that function to lift loads and set them outside of the tipping range of the machine. Some machines also came with load locks on the arm and boom cylinders. These units used pilot pressure from the joy sticks to unlock a valve that held oil in the lift side of the cylinder before it could set the load down. There were no load lock valves for the bucket circuit that I am aware of and I can't think of any check valves in either arm or bucket circuits.

As Hydaumind says "what are the symptoms you are experiencing"?

 

[Jon_one]

well . the reason i think that is because a couple years ago we had a guy come in and mess up everything . i think he adjusted them to try to change relief pressures etc .. but he failed miserably . machine was never the same . he took out the control valve three times . rebuilding it twice because he swore that was the problem . we even bought a new control valve and he messed that up . he made us buy a new pump trying to solve this also..

all of this was done because he got a reading of 750psi from the "main pump" .. which was actually the pilot pump and he swore it was the main pump...

the initial problem we had before all this was dying down and black smoke while digging ... i was much younger then and not into it that much . but now he messed us up really good . and i have spent alot of time trying to solve this i have done everything by the book and noticed that if this guy could think that the pilot pump test port / assembly was main pump pressure maybe he adjusted all those safety suction valves thinking they were all main pump reliefs ? and this is not in the book ...

when i look at them they looked tampered with ..

The only functions that reach relief pressures are the arm which is slowish 360-380kg/cm2 , the bucket which is kind of normal except killing machine engine alot when relieved 320kg/cm2 or around there , black smoke etc. TVC valve is not responding to adjustment and the boom which is slow on raise but does reach relief pressure and also kills the engine when relieved , i was thinking maybe it is slow due to a bad LS-EPC valve which i have a new one on the way.. swing goes to 266kg/cm2 . one track hits RH 240 and the other LH 140 . what i did notice today is that when tracking or lets say when relieving the LH track the arm does not pass that pressure when relieved (same pump) only when track lever is let go arm reaches relief pressure ...


i checked main relief valves , i checked TVC solenoids . i checked pilot pressure , i checked main pump pressures directly . i checked 2 stage relief valve , i changed LS shuttle Valves for arm and bucket group , i checked pressure compensation valves but were not too sure about them . i know the right ones were in place but not sure of there operational status (what to look for etc) , i adjusted TVC valves countless times (rear pump recently started to not take adjustment and kill the engine) i have a spare .. i suspected swivel joint but i doubt it .. tracking issues show when tracking / relieving in both directions . same readings also ..

machine tracks fast on level surface , responds quickly . weakness shows up when climbing . sometimes it wont even move up rough hills and just stay at there low reliefs and we have to use bucket / arm to help ..

so after all this i thought about the suction valves / port relief valves ...

 

[Hydraumind]

You need an expert to help you doing the job, this is the fastest way. A good way to start is to have a good mechanic flowmetering the pump and adjust it again as factory set if it is still in good shape in other word not leaking. Then you can continue with pilot system and of course the main control valve.

 

[Jon_one]

You need an expert to help you doing the job, this is the fastest way. A good way to start is to have a good mechanic flowmetering the pump and adjust it again as factory set if it is still in good shape in other word not leaking. Then you can continue with pilot system and of course the main control valve.

ok i understand that . only problem is i am probably the best Komatsu guy in my whole country right about now .. i could probably find a expert that works with cat or something to help me do the flow metering ..

i did have the pump working good at one point . but the machine was parked for a while and i am guessing that something got stuck in the strainer / filters for the TVC valve on the rear pump so maybe that is why i am not getting adjustment ...

i am sure if i get a main control valve to just swap out i will be better off ...

i was wondering if the spools are mixed up for some reason .. would this cause these issues ?

 

[John C.]

Sounds to me like you have a world of issues to try to solve. I don't think there are many anywhere that could provide the kind of information you need to solve all the issues. What was changed in the pumps? Are all the valves and cartridges installed in the right places? Is there something plugging up some sensor lines? Are the electronics hooked up and set up properly. Were it my problem I would start at the pump and make sure it is working properly before anything else. You can use the speed of the tracks as a poor man's flow meter as long as the swivel and travel motors are working properly. Some kind of timer is necessary. Paint one pad on each track. Pick up that side of the machine with the implements, put the travel in high speed mode. Start the track turning to full speed and start timing the revolutions after the track has made a full revolution at speed. I used to do three turns to time. This will at least show you which pump is low and by how much. The pressures you are giving are way out of spec. Pilot pump pressure as I recall was 425 PSI. Implement pressures in normal mode were 320 KGCM2 or about 4,500 PSI and in travel or power max should be around 360 or around 5,100 PSI. The scenario you are describing tells me the pumps are not destroked at the proper pressures.

The one thing that has not been addressed in your post is the compensator valves. We didn't have much trouble with those in the 200 class of machine like the 300 class but at times they were an issue. They can be resealed but most people of that era just replaced them. If one leaks through then the problem shows up on most all the functions. You might try swapping one from each side of the valve and then check something that doesn't involve two pump function. One track at a time locked up so it goes over relief might do the trick.

I'll keep thinking a bit about this and let you know if anything else come to mind.

Good Luck!

 

[Jon_one]

Thanks alot.

i will start at the pump and work my way up . they bought a whole new pump assembly in error .

i saw in another one of your posts that when the arm and boom are working together , arm in & boom raise , boom would come to a complete stop . i do experience this . this is why i thought about the check valves for arm and boom circuit .. sometimes it will get a little faster while pulling in the arm . but the boom is not too much faster when operated by itself anyway .


i was thinking maybe something is out of place somewhere .. like a mixed up spool arrangement ?
the press compensators are all in the correct places i did check this . but i think they may need re-sealing i am not sure . i did a little test with my finger covering the hole on a few of them whilst i pressed the assembly in to check for leakage . it seemed fine but that is in a low pressure situation .. so i will consider this . maybe see if i can get a seal kit for all of them .

by the way i do have pilot pressure within spec now. that test they did was a longtime ago when they initially messed up the machine .

i checked the safety suction valves /port reliefs today . they all seemed fine .

what can cause the tvc valve for the rear pump assembly to not respond to adjustment ? this pump never crosses around 320kg/cm2 when using bucket relief so maybe the relief is set properly for this one .. but it does not de stroke i think and it kills the engine under load .i tried adjusting the valve according to the manual. but only the front pump (arm group) responded correctly to the adjustment . i adjusted the TVC valve for bucket group numerous times trying to get feel with machine on while some one was relieving the pump on and off while i did it . The funny ting is the pump for the arm develops the same pressure and more and it does not kill the machine . i guess it is because that one is working better . engine speed drops from 2150rpm to about 1850rpm while maintaining 380kg/cm2 (which i need to fix tomorrow to 320) ( also need to adjust the Tvc on this to get the engine speed to spec while on arm relief )

i do have a spare TVC valve assembly so i will consider swapping it to see if i get any change with respect to the dying down issue ..

Thanks alot for all of the support . i just hope i don't end up having to pull out the control valve to get to the check valves !

 

[Jon_one]

ok so today i changed the TVC - LS valve . adjusted main relief for arm and bucket group to spec . machine generally feels better because he TVC valve for bucket group was faulty and causing the machine to die down unnecessarily ..

what i did notice today is this . if the arm is pushed out while using boom raise the boom goes up much faster .. i am trying to figure out why this happens ..

when arm in is used the boom is slowed down totally .

 

[John C.]

I'm trying to figure out what you mean by TVC valve for the bucket. As I recall the TVC stood for Torque Variable Control and that was on the pump. I'm not aware of anything like that on the an individual circuit. There was a variable control for an auxiliary function like a thumb that was an option back in those days.

What is the serial number of your machine?

 

[Jon_one]

I'm trying to figure out what you mean by TVC valve for the bucket. As I recall the TVC stood for Torque Variable Control and that was on the pump. I'm not aware of anything like that on the an individual circuit. There was a variable control for an auxiliary function like a thumb that was an option back in those days.

What is the serial number of your machine?

A80771

when i say bucket group i mean all of the associated functions on that pump . service manual refers to it as this .
anything associated with rear pump is bucket group (bucket , RH track , Boom). anything associated with front pump is arm group (arm, LH track , swing) ..


tvc valve for bucket group was stuck or something and not de-stroking when necessary therefore killing the engine when digging and raising boom but arm pressures were good and maintaining pressure while relieved and not killing the engine . i changed this assembly and it is fine now .

 

[John C.]

I was hoping that I was just mis-understanding the terminology. My brain cells are getting a bit worn and I thought I might have forgotten things more than I had.

Sounds like you have the machine at least in a working condition now. Good Work!

I'll have to study a book before I could comment on the boom and arm speed issue. Have you tried the cycle time test on your tracks yet?

 

[DK88]

Is that the one has the 22mm jam nut and an eccentric spool with a dot on the end?

 

[Jon_one]

I was hoping that I was just mis-understanding the terminology. My brain cells are getting a bit worn and I thought I might have forgotten things more than I had.

Sounds like you have the machine at least in a working condition now. Good Work!

I'll have to study a book before I could comment on the boom and arm speed issue. Have you tried the cycle time test on your tracks yet?

haven't had time to do the cycle test yet . yes machine actually works now it is just a bit slow .

i have made a major break through yesterday . The LS lines and Main pump lines where not mounted in there correct positions ..
i then checked solenoids and pressure sensors associated with the Main pump and Computer to ensure they were not mounted incorrectly ...

since i swapped the LS lines and main pump lines the machine has alot more power . but is still on the slow side all around . I am guessing it needs tweaking / tuning ?

I still have one track that is low on power compared to the other . what i noticed with this issue is that when i relieve the side with the least power (Front pump) i get the other pump building the same amount of pressure that the front pump builds ..

but when i relieve the other side which gets a decent amount of pressure (not full but closer) 260-280kg/cm2 this does not happen .. the front pump remains at unload pressure

so lets say i get 150kg/cm2 on the front pump while relieving left track . the rear pump also acts like it is getting a signal to stroke up . so it builds pressure to 150kg.cm2
if i hold the lever or use other functions the front pump would momentarily gain more pressure and also attempt to track with more power.. but it seems like something is restricting it somewhere .

this pump is good i think the problem switched sides when i swapped the main pump lines ..

what i want to know is if incorrectly placed spools will cause some of my issues ? i think that maybe they are incorrectly placed .
anyone has any information on the spool placement ? the shop manual does not go into too much detail with this .

 

[Jon_one]

Is that the one has the 22mm jam nut and an eccentric spool with a dot on the end?

yes that is the adjustment point for TVC

 

[John C.]

The travel circuits are separated unless another function is used. I'm thinking that something is making the merge valve open when it shouldn't.

 

[Jon_one]

makes sense . i was wondering if the LS portion of the merge valve is sticking ..

 

[Jon_one]

do you think that spools placed in wrong places can cause some of my issues ?

 

[Jon_one]

ok so another small update is when the track lever is moved on the problem side the pump doesn't even stroke up . it just sounds like nothing is happening . the engine tone doesn't change or nothing .. its like the system is at idle . the other side on the other hand seems normal ..