Testing and repairing hydraulic pump

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Re: Testing and repairing hydraulic pump

Postby SvendH » Tue Sep 10, 2019 10:38 pm

As Henk says,it is more easy to measure pressure at the cover (and safer) but if the pressure is low-how do you know if the problem is in the pump or in liftsystem? :?
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Re: Testing and repairing hydraulic pump

Postby Major1955 » Wed Sep 11, 2019 6:20 am

SvendH wrote:hi
I think you need to run a test of the pump itself "in tractor",ram and cover off,then fit an outlet pipe to the pump itself with handoperated "strangle-valve"+your preassure gauge.This should give you a realistic picture of the pumps capacity and perhaps remove some unknowns from the equation :D
This is only a procedure for the man who knows what he is doing !!


Last weekend I tested the pump when it was bolted to tractor. I tried to measure the pressure directly from pump, without rear axle cover, with my adapter for pressure gauge. Adapter had two welded "legs" to rear axle and it was bolted to it. During test adapter were able to tilt while pressure was increasing. That caused O-ring blow up around 100 bar. I was hiding behind rear wheel and able to react in second and press clutch again. I would not recommend test to anyone :lol:

Next I installed the rear axle cover to tractor and tested without valve assembly. Measurement was done directly from pump outlet pipe. Result was around 150 bar.

Then I installed also valve assembly and pressure was only around 70 bar and lift didn´t work with load. Without load it worked well.

So I think pump is OK and problem is in valve assembly or ram cylinder. My latest photos are about dissambling of valve assembly, but I didn´t find any thing what could explain this behavior.
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Re: Testing and repairing hydraulic pump

Postby SvendH » Wed Sep 11, 2019 2:03 pm

Well the pump Should be ok then,how About the the valve that dumps the lift perssure when you select "down"?
Could it be sticking. It Should move easy and yet seals properley in bore
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Re: Testing and repairing hydraulic pump

Postby henk » Wed Sep 11, 2019 8:38 pm

An idea, remove evry thing from the valve assembly and blow some are trough all the holes. See if some route is blocked. Could be dirt or a bit of white tape to seal a connection that went in a chanel and is obstructing something.
Kind regards, Henk

Fordson New Major February 1957 Mark I
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Re: Testing and repairing hydraulic pump

Postby shepp » Wed Sep 11, 2019 9:07 pm

henk wrote:Correct me if I'm wrong, but on the cover of my Major is a connection for a user, direct from the pump. Red arrow on the picture. This could be a place to put a gauge.
Image

The plug referred to by henk is an oil passage plug. The passage is created during the machining of the lift cover casting to take the oil under pressure from the stack tube that comes up from the pump and into the lift cover where it is sealed with an "O" ring, and then forward through the casting into the horizontal tube which is sealed with an "O" ring at each end and then into the control valve assembly.

You could put a pressure check gauge in at this point with a non return valve, and then operate the lift lever and see what maximum pressure is recorded. However this pressure would be dependant not only on the condition of the pump, but also the condition of everything else further down the line, such as the relief valve, the check valve, the spool valve, the cylinder seals, the oil tubes and all the "O" ring seals. It would not tell you any more than simply putting a pressure gauge on the jack tapping on the control valve body.

The procedure that Major1955 has done in going straight onto the inlet pipe from the pump with the valve block off will have given a true value of pump pressure, and at 150 bar or around 2250psi that is a reasonable pressure. So the problem is either in the relief valve, the check valve (and I would look closely at that as it is something that gets overlooked), the spool valve, the cylinder seals and the cylinder itself, or the "O" rings.
1946 E27N, 1952 Major Diesel, 1959 Power Major, 1962 Dexta, 1962 Super Dexta, 1963 Super Dexta NP, 1964 Super Major NP, 1965 Super Dexta 3000, 1966 Major 4000, 1967 3000 PF, 1994 5640,plus Basildon built NH.
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Re: Testing and repairing hydraulic pump

Postby Major1955 » Thu Sep 12, 2019 6:16 am

henk wrote:An idea, remove evry thing from the valve assembly and blow some are trough all the holes. See if some route is blocked. Could be dirt or a bit of white tape to seal a connection that went in a chanel and is obstructing something.


Good idea. I already dismantled whole valve assembly, or at least all parts which can be removed without hydraulic press. All photos about the dismantled valve assembly are in my previous post. Next I need to test the compressed air to clean all channel in valve body.

Can problem be one of valve springs? Pictures 1. and 6.

Or is there some O-ring which is totally missing from my construction? For example picture 6.

If someone has other ideas I can take more pictures.

Maybe this thread can also help someone else in future :lol:

Thanks!
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Re: Testing and repairing hydraulic pump

Postby oehrick » Thu Sep 12, 2019 11:30 am

Summarising so far
You have cleaned and checked the pump intake so there is no probability of being starved of oil
You have had movement of the arms (without loading) so there is no mechanical problem like seizure in the ram or linkage
With the pump output dead headed by the test gauge you develop only 70 bar at low revs and 350 bar full revs AT NO FLOW OF OIL - while this is similar to the PRV blow pressure, the PRV was not in the system at the time.
This leads me to the following

The pump is leaking internally and only manages to develop system pressure with no output - Normal flow rate should be in the order of 5 gallons a minute. (I would expect pressure to rise until the gauge Bourdon tube or flexi hose to blow against a dead headed pump with nearly 50 hp driving it)
The pipe from pump to top cover where the gauge was connected or the cover is leaking the full output of the pump at full revs
Something in the pump drive is slipping so the pump gears do not run to speed as the load increases.

I've our old Super Major pump still kicking around somewhere, would barely lift the front end loader, tried most of what we have been through here and looked unscored inside compared to yours, but the accumulation of wear had done its worst - eventually fitted one off a tractor being broken for bits and the difference was amazing.

If the above captures the key things you have done, I fear the time has come to try another pump or at the very least get this one tested - I know some folk enjoy weightlifting and pay Gyms for the opportunity but I expect you are heartily fed up with playing yo-yo's with that top cover :(
Best regards
Rick - Bogside on Bure


1958 Diesel E1A Mk2 s/n 1470165 - still in working clothes
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Re: Testing and repairing hydraulic pump

Postby Major1955 » Thu Sep 12, 2019 1:24 pm

oehrick wrote:Summarising so far
You have cleaned and checked the pump intake so there is no probability of being starved of oil

Yes
oehrick wrote:You have had movement of the arms (without loading) so there is no mechanical problem like seizure in the ram or linkage

Yes and also movement with 200-300 kg load (Only high revs)
oehrick wrote:With the pump output dead headed by the test gauge you develop only 70 bar at low revs and 350 bar full revs AT NO FLOW OF OIL - while this is similar to the PRV blow pressure, the PRV was not in the system at the time.

No.
Pump output dead headed (No valve block at all, only output of pump, no return) and engine idle revs 100 bar and engine with half (1/2) revs 150 bar. See pic on my post at "Sat Sep 07, 2019 5:40 pm"

After this test I removed pressure gauge and re-fitted valve block. I have another measurement output while valve block is in use (can be seen in Picture 8.) I fitted my pressure gauge to it.
Result:
Worked when no load
With 450kg load, no movement, engine idle pressure zero bar. Engine full revs pressure 70 bar.

After this I took valve block and dismantle it and took pictures 1-8.

I´ll hope this helps to understand the whole story :D

My opinion is that pump works but something in valve block leaks the pressure. But I don´t find what leaks :( Tonight I´ll check "henk"s idea.
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Re: Testing and repairing hydraulic pump

Postby oehrick » Thu Sep 12, 2019 7:38 pm

OK, thanks for the confirmation, things tend to get lost between postings and this one is not proving easy to diagnose ;(

My point is that when new the pump should support more than the 350 bar at a flow rate of 5 gallons per minute (the manual does not specify at what revs and 2200 psi is 149 bar), any surplus shed via the PRV if you can't reach 350 bar with no flow of oil at anything other than full revs then the conditions I noted either singly or in combination are occurring, this is why a bench test by a hydraulics firm who can see the pressure developed against rate of flow would give a reliable answer, you need both for the system to work.
For comparison my '58 major will pick up a transport box with enough weight in it for the front wheels to come off the ground, it will lift the arms until the mechanical limit is reached and then I can hear the PRV discharging, at tickover it may slow the engine enough to stall it, at 1000 rpm you can hear the speed drop - it is all original parts. the back end is full of the usual 'yoghurt' of emulsified oil.

I don't know how much you know about hydraulics so apologies in advance if I'm saying what you already know. A gear pump is a positive displacement pump, the gear form is designed to take a slug of oil per tooth and pass it to the output, the output varying with the revs, any wear in the teeth, sides of the gear or housing will allow leakage as you cannot compress oil, when the clearances get sufficiently large and the pump is dead headed the pressure will rise until it is equal to the force needed to squeeze it through the gaps until it ends up just churning the oil. (unfortunately not testable on the Major but an internally leaking pump will often run at a significantly raised temperature, the energy going in to turning it from the engine re appearing as heat where the pressure drops and the friction takes place, same is true for leaky valves)

Not sure where you are located so it may not be easy to get to an outfit that can test the pump, so if you go back to your test on the pump alone but incorporate a Tee before the gauge and a fine needle valve with a spill pipe to a clean container you will be able to get a rough and ready result that indicates the health of the pump, gently open the valve so the oil weeps out and see how far you open it for the pressure to fall 10 bar and measure how much oil is delivered in a minute, repeat dropping another 10 bar by letting more oil flow. Lets say for sake of argument that a worn pump might reasonably perform at half new condition, it will tell much at what pressure it will sustain a flow of 2-3 gallons a minute.

Hope that makes sense and is helpful
Best regs
Rick
Best regards
Rick - Bogside on Bure


1958 Diesel E1A Mk2 s/n 1470165 - still in working clothes
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Re: Testing and repairing hydraulic pump

Postby SvendH » Thu Sep 12, 2019 10:45 pm

Rick is right,
Rig a stout pipefitting direcktly to the discharge port of the pumpe,fit a tee with manometer and a discharge pipe with a valve so that you can build pressure while monitoring the discharge rate.You should be able to make several gallons per minut at 150-250 bar,with a healthy pump!
Start with engine at idle and graduly work up.Be Carefull!!
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Re: Testing and repairing hydraulic pump

Postby Major1955 » Fri Sep 13, 2019 6:47 am

Thanks, I understand your point. I´m 100% sure that my pump characterics are not even close comparing new one :D but 500kg lift would be just enough for me. I understood that valve assembly has unloading valve with pressure setting of 2200psi/150bar? Please correct if I´m wrong.

But, if we we compare my measurement to real life.

See Fig 184 on file page 5 or document page 151. http://www.fordson.se/5_Hydraulik_Verks ... 47-166.pdf

In my case, when valve assembly is fitted on and try to lift. Ram doesn´t move from low position (because of load) and the valve control lever is on up/raising-position. System is in "Condition when raising"
If valve assembly doesn´t have any leakage, and unloading valve stays closed, that would be also similar dead headed-situation for pump? And pressure should be same as my measurement? Or is there return flow while "Condition when raising"?
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Re: Testing and repairing hydraulic pump

Postby oehrick » Fri Sep 13, 2019 1:24 pm

Hi,

I think you may still be missing my point, the 150bar dead headed reading being the confusing point because of the similarity with the PRV limited system pressure. Perhaps an electrical analogy might help.
You have a battery showing 150 volts when not connected to anything but the meter. Connect a bulb, it glows, consumes a tenth of an amp at 150 Volts, the battery voltage drops to 149 volts. Connect a starter motor instead, it consumes 20 amps at 150 volts with no load, motor spins - voltage drops to 100 volts. Engage motor to engine and repeat, motor consumes 100 amps at 150 Volts under load, voltage drops to 50 volts, motor warms a bit but does not turn, is the problem in the starter switch ?? (volt / current values not calculated!)

If I put a 200 bar gauge directly onto the pump and revved the engine I would expect the gauge to blow apart, pressure and flow are proportional to revs and torque, your pump is only reaching top pressure with the engine revving and producing no flow between your test point and the pump gears, to me this implies
Pump loosing several gallons per minute oilflow internally through wear or damage leakage.
Pump piping loosing same oil volume
Pump gears slipping or otherwise not turning at the correct revs as pressure develops
Oil starvation to pump input
Temporary suspension of the laws of physics in your postcode ;)

None of these excludes a further fault elsewhere in the control circuit as well BUT you measured the data with your gauge plugged into the top cover and no PRV, Lift valve, check valve etc Replacing the bulb, switch or wiring in a flashlight will not give much light if the battery is flat :(

I am at the end of what I can think of to suggest for you to try next without causing further confusion, if you can get it to a pump specialist do so, if not, try the rough and ready flow : Pressure test suggested, your test adaptor plate shows clearly that you can make parts for testing that are safe and functional, third option is finding a spare pump but unless you can be sure the seller is offering a genuine worker ............

Hope you can get it resolved without too much more aggro, at least by the roman candle from your exhaust the rest of the tractor is lively enough!
Rick
Best regards
Rick - Bogside on Bure


1958 Diesel E1A Mk2 s/n 1470165 - still in working clothes
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Re: Testing and repairing hydraulic pump

Postby Major1955 » Sat Sep 14, 2019 4:09 pm

Thanks Rick! I do understand your point.
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