801.4 Dipper Arm Lacking Power

[Bradders8014]

Happy new year to everyone.....new year, new problem!!

I have a problem on my 1996 JCB 801.4 very similar to Hankstains.
I am suffering from a slight lack of power on the dipper arm. When I say slight the machine still operates but is lacking in power compared to other functions. It is the same whether drawing the dipper in or out.
What I have noticed is the same as Hank, if I introduce a second function it seems to increase power in both.
For example when digging a trench and drawing the dipper arm in under load it will come to a stop, if I then introduce a second function such as lifting the arm whilst still drawing in the dipper it increases power to a level you would expect (enough the pull the machine towards the trench if not released). This wouldn't happen with the dipper function alone.
It isn't piped for aux equipment, I've changed all the fluids bar the hydraulic oil (level is fine) and all the filters have been changed.
There are no visible leaks to the hoses or rams. Everything else works just fine.
I accept that she is getting on a bit but it seems strange how there is extra power when two circuits / functions are used.
This has always been the same since I have had it.

Thanks in advance

[v8druid]

Happy new year to everyone.....new year, new problem!!

I have a problem on my 1996 JCB 801.4 very similar to Hankstains.
I am suffering from a slight lack of power on the dipper arm. When I say slight the machine still operates but is lacking in power compared to other functions. It is the same whether drawing the dipper in or out.
What I have noticed is the same as Hank, if I introduce a second function it seems to increase power in both.
For example when digging a trench and drawing the dipper arm in under load it will come to a stop, if I then introduce a second function such as lifting the arm whilst still drawing in the dipper it increases power to a level you would expect (enough the pull the machine towards the trench if not released). This wouldn't happen with the dipper function alone.
It isn't piped for aux equipment, I've changed all the fluids bar the hydraulic oil (level is fine) and all the filters have been changed.
There are no visible leaks to the hoses or rams. Everything else works just fine.
I accept that she is getting on a bit but it seems strange how there is extra power when two circuits / functions are used.
This has always been the same since I have had it.

Thanks in advance

ram seals by-passing internally ... additional service is allowing greater flow to the port and compensating for by pass perhaps .... extend dipper fully and sit on the floor....disconnect pipes and cap pipes and ram ports ... then lift into the air with the boom, about a foot ...... it should sit there rock solid ... if it creeps the seals are bypassing internally

[ianoz]

Depends how bad it is . Any hydraulic ram will stall out if the ground / conditions are hard enough . By lifting the boom your reducing the amount of material you are trying to force the bucket through .So then it can continue cutting through the ground .
I don't know how experienced an operator you are , but when i dig i try and take 100 mm layers out .. this makes it easier on the machine , and helps keep the trench from breaking out the sides .Buckets size makes a big difference to . a 300 mm bucket will dig easier than a 600 mm bucket .
But as Graham said ram seals do wear out /fail , but usually when they do the ram will creep as it bypasses as grahams test will show .

[Bradders8014]

Thanks both for the advice, I suspect I am probably asking a bit much of the old girl. In the past I have always hired, which of course have been nearly new machines which have way more power than mine. This is the first one I have owned so I probably don't really know what to expect of something nearly 25 years old.

I am intermediate experience wise but I do get idea around digging in layers for ease and not just diving in and going for a full bucket first time breaking the trench edges.
I understand what is being said about bucket size, I am currently using an 18" bucket with teeth.
I am due to dig further trenches for utility services in the next couple of weeks so I'll hold off for now and see how I get on. If it's an issue I'll check the seals as described.
I just thought I would ask as there is a noticeable difference in power between the dipper and other arm functions.
Once again thanks guys.

[Hankstains]

Sounds like my problem

ram seals by-passing internally ... additional service is allowing greater flow to the port and compensating for by pass perhaps .... extend dipper fully and sit on the floor....disconnect pipes and cap pipes and ram ports ... then lift into the air with the boom, about a foot ...... it should sit there rock solid ... if it creeps the seals are bypassing internally

Hey V8druid, sounds like you may have nailed it, just out of curiosity, should my boom stay up if I turn the engine off, mine seems to drop very quickly, say half an hour to drop 5 foot.
Also trying to find out where/how the fault code appears on the puma unit? does it show up on the unit where it says test 1 test 2 and the hours etc, I have 2 beeps but can't see a code. sorry to be a bit off topic, a bit like chatting down the pub, end up talking about all sorts of rubbish......I'll have another pint I think..
cheers
Hank

[v8druid]

Hey V8druid, sounds like you may have nailed it, just out of curiosity, should my boom stay up if I turn the engine off, mine seems to drop very quickly, say half an hour to drop 5 foot.
Also trying to find out where/how the fault code appears on the puma unit? does it show up on the unit where it says test 1 test 2 and the hours etc, I have 2 beeps but can't see a code. sorry to be a bit off topic, a bit like chatting down the pub, end up talking about all sorts of rubbish......I'll have another pint I think..
cheers
Hank

Almost certainly ram seals

Muz is your man for the PUMA stuff