l785 weak loader. Weak pump pressure?

[muddy94chevy]

Hey guys a while back I posted about bucket drifting down but did not get any where with that problem, except for that it doesnt do it at full rpm. But I used it a little more and actually the hydraulic power for the boom/bucket seems weak. Including the AUX hydraulics. If I gently push back on the heel of the boom raise circuit I can actually lower the boom all the way to the ground, without an attachment. So I noticed that I have an elbow that has a 1/8in fitting on it, so I hooked up my gauges to that port. At full throttle control valve in neutral, I have 500psi. I lift the bucket to full height and hold it there and watch my gauge, I had 1900 for a second then 1500 and it kept dropping off as long as I held that control valve, all the way down to 1200psi. Do I have a weak pump? My travel hydos are strong and responsive and my 2 speed works good. In my above test, which I am not sure if I did something wrong or not, my control valve got really warm, not too hot to touch, my pressure relief valve was not warm at all. Does this indicate anything? That maybe its the control valve? Do you think it could be the pressure relief valve? Sorry for the long post just trying to get this thing working as good as it runs now (did a full rebuild on the engine icluding new crank and a rod) P.s. maybe I am wrong but I think the skidsteer should either pick up whatever I am trying to lift or it will tip forward no? Mine never came close to tipping and I couldnt even pick up about 1500or so pounds. Thanks for any help!

 

[Tazza]

I'd tap into your aux hydraulic fitting, put your gauge there and operate the aux hydraulics to get a true pressure reading. You should get the machine nice and warm, you want it at operating temperature to give an accurate reading, when cold, the oil is thicker so will give a higher reading.
I don't know what your pressure should be, but i'd suspect around 2,500 psi

 

[muddy94chevy]

I'd tap into your aux hydraulic fitting, put your gauge there and operate the aux hydraulics to get a true pressure reading. You should get the machine nice and warm, you want it at operating temperature to give an accurate reading, when cold, the oil is thicker so will give a higher reading.
I don't know what your pressure should be, but i'd suspect around 2,500 psi

Ok thanks Tazza. I will check there and post back my results. Is it common to have a weak pump but strong forward and reverse on the drive?

 

[muddy94chevy]

Ok thanks Tazza. I will check there and post back my results. Is it common to have a weak pump but strong forward and reverse on the drive?

Well I hooked up my gauge to my aux line on the right ofmy machine as I sit inthe seat. It was warmed up and full throttle I get 5-700 psi when i let the relief valve hit and hold the aux open.

 

[muddy94chevy]

Well I hooked up my gauge to my aux line on the right ofmy machine as I sit inthe seat. It was warmed up and full throttle I get 5-700 psi when i let the relief valve hit and hold the aux open.

Tazza, maybe i misunderstood. I dead headed the pump withall my texts. Were you wanting me to tee in to the aux hydraulics and use an attachment? If so i don't have one. But yesterday to get it warmed up I was moving branch chippings. Mind you have the bulk material bucket, but i had a hard time scooping a full bucket out of the pile. I would have to either layoff the control valve and apply it again and repeat or back up as I am lifting or curling. Both were the same.

 

[JWD]

Tazza, maybe i misunderstood. I dead headed the pump withall my texts. Were you wanting me to tee in to the aux hydraulics and use an attachment? If so i don't have one. But yesterday to get it warmed up I was moving branch chippings. Mind you have the bulk material bucket, but i had a hard time scooping a full bucket out of the pile. I would have to either layoff the control valve and apply it again and repeat or back up as I am lifting or curling. Both were the same.

Have you checked the hydraulic filter screen under the seat to make sure it isn't clogged up? My L785 will lift 2000 pounds easily without tipping.

 

[muddy94chevy]

Have you checked the hydraulic filter screen under the seat to make sure it isn't clogged up? My L785 will lift 2000 pounds easily without tipping.

Yes cleaned that really well. Both hydraulic filters are new. Last night I took apart the relief valve in the control valve and shimmed it. My pressure at that 1/8in plug port is around 1700 and is now alot better. Might go one more washer some day

 

[Tazza]

Yes cleaned that really well. Both hydraulic filters are new. Last night I took apart the relief valve in the control valve and shimmed it. My pressure at that 1/8in plug port is around 1700 and is now alot better. Might go one more washer some day

The idea was to dead head the aux coupling with the gauge, nt to T into it. You can never dead head the pump directly, you need the relief in the line or you will break something so the aux ports are an excellent test point.

 

[muddy94chevy]

The idea was to dead head the aux coupling with the gauge, nt to T into it. You can never dead head the pump directly, you need the relief in the line or you will break something so the aux ports are an excellent test point.

Ok so I did whatyou asked for then. Yes I did say deadheaded pump but I misspoken. I just wanted to clarify that you wanted me to put a gauge on the end of the line and not tee into it and use a hydraulic attachment. Guess i thought maybe I misunderstood you when i did not get a response from that test.

 

[Jim A]

Take hydraulic pump off (only small charge pump runs boom and bucket and aux two bolts hold it on drive pumps)
check Wear plate plastic seals spaghetti like square oring for damage.
Mine did same after running hydraulic hammer for hours got it hot blew internal plastic seals .
Ps CNH does not have rebuild kit for mine I had to buy new pump $700 because a $5 unique seal blew.
.