Volvo EC20 Engine stall under load

[Ben.Martins]

Hi guys,

New to the site and loving the wealth of information that is here. Have a great admiration and respect for hydraulics guys and always been something I've wanted to learn more about. Am hoping to learn lots of new things that will help me become a better technician. Have maintained plant and agricultural in the past but only just starting to dip my toes into the world of hydraulic analysis. So, apologise if some of my terminology is a little off!

Onto my first post then! So, I've been looking at a Volvo EC20 mini digger which has an engine stalling issue when the hydraulic system is put under load. This has lead the operator to have to feather the controls in order to prevent this but obviously isn't particularly practical! If the stall happens the engine can be restarted easily and i am happy that there isn't a mechanical issue with the engine itself. No smoke, no noises, starts every time hot or cold.

Not being able to find a great deal of information on this model I guess I would like to know if anyone has any info on the accumulator that sits under the seat? Also if the pump has a variable swash plate, although looking at the pressure's when operating it does seem that it is being controlled as there is a gradual increase in pressure. However, I may have got this completely wrong so do forgive me! Looking at some initial results I can see that the peak pressure when the engine stalled from the minimess port closest to the front of the cab on the valve block, reached 178.3 Bar. This seems a little low to me to stall the engine so I am wondering if there could be another reason for the engine to cut out. The relief valves have obvious signs of being adjusted at some point in there life as we would expect to see!!

As I said, still finding my feet and any help would be gratefully appreciated.

Kind regards

Ben

[Muz]

The pressures are not far off, should be a little higher, but that wont improve your problem, someone has screwed out the MRVS to max so it is stalling possibly. The engine is the same as in the EC15's which is a mitsubishi L3e. Maybe a stoopid question but .. I take it the engine is running at full revs ? Its quite easy to stall that machine if the revs arent set correctly especially when tracking and spragging.

Theres no tacho, so its hard to say what yours is running at without hearing it, all you can do for that, is record it on your phone, post to youtube and share a link to it here ?

Oh and welcome BTW

[v8druid]

certainly sounds like the MRV is max-ed out and unable to dump before the motor's overcome Muz ... effectively dead ended.

Great trying to sort other ppl's bodgery

I'd be tempted to wind the MRV out a few turns and get it to run without stalling, then re-set pressures with the gauges

As for revs ..... can buy some decent lil' optical tacho gauges for a tenner on ebay .....

[Muz]

As for revs ..... can buy some decent lil' optical tacho gauges for a tenner on ebay .....

I thought I'd heard something about these somewhere .. what would they index off ?

[v8druid]

I thought I'd heard something about these somewhere .. what would they index off ?

Refective optical tape, 10mm square target, stuck to crank pulley, or anything suitable Muz Bought one to re-set the 'Drema's auto throttle settings, which were way out. Targets came with the meter

Mutt's nuts TBH ..... I'll find the details and get you some pix ..... VERY handy tool

Put a new target on the crank pulley ..... then discovered one already on there

gone up a bit ...........

http://www.ebay.co.uk/itm/LCD-Digita...cAAOSwxvxW8c34

[Muz]

so .. I assume you must give it the diameter of the pulley accurately so it can calculate the revs ?

[v8druid]

so .. I assume you must give it the diameter of the pulley accurately so it can calculate the revs ?

No Muz ..... a revolution is a revolution, no matter what the diameter of the pulley and if it does 1000 revolutions in one minute, its 1000rpm

there's only one target on the rotating item to point the laser at and read back from

[Muz]

No Muz ..... a revolution is a revolution, no matter what the diameter of the pulley and if it does 1000 revolutions in one minute, its 1000rpm

Yes .. my brain is wired slightly differently to some folks, Ive just been theorising about a fly wheel which you look at face on and put three reflective patches on it from the crank outwards, the outer one will read the same as the inner one yet it travels a far greater distance .... I must stop thinking about planets

[v8druid]

Yes .. my brain is wired slightly differently to some folks, Ive just been theorising about a fly wheel which you look at face on and put three reflective patches on it from the crank outwards, the outer one will read the same as the inner one yet it travels a far greater distance .... I must stop thinking about planets

LOL in terms of feet per minute traveled I'd agree, but as you say in rev.s per minute .....

[Ben.Martins]

The pressures are not far off, should be a little higher, but that wont improve your problem, someone has screwed out the MRVS to max so it is stalling possibly. The engine is the same as in the EC15's which is a mitsubishi L3e. Maybe a stoopid question but .. I take it the engine is running at full revs ? Its quite easy to stall that machine if the revs arent set correctly especially when tracking and spragging.

Theres no tacho, so its hard to say what yours is running at without hearing it, all you can do for that, is record it on your phone, post to youtube and share a link to it here ?

Oh and welcome BTW

Hi Muz and v8druid,

Thanks for the welcome and thanks for the response! Sorry not replied sooner but I really do appreciate your input. I've come from an Automotive background and have been using a PicoScope and acquired an optical pick which means I can get what has been suggested, RPM from the crank with reflective tape and then graph it. Have recorded Max RPM at just under 2500. Unsure if the this is limit on this engine as can't find anything about it but I would assume it wouldn't be much higher than that by the way it sounds. Now with regards to the MRVS, and please forgive me for my naivety, but if they don't operate correctly or have been maxed out how does this cause the engine to stall if the pressure I've recorded isn't far off? Sorry for what would appear stupid questions but am trying to figure out in my head this system works. Can't fix it till you know how it works right?!

Again, appreciate the input and looking forward to learning more.

Ben

[Ben.Martins]

Digger rpm.jpg

[v8druid]

Hi Muz and v8druid,

Thanks for the welcome and thanks for the response! Sorry not replied sooner but I really do appreciate your input. I've come from an Automotive background and have been using a PicoScope and acquired an optical pick which means I can get what has been suggested, RPM from the crank with reflective tape and then graph it. Have recorded Max RPM at just under 2500. Unsure if the this is limit on this engine as can't find anything about it but I would assume it wouldn't be much higher than that by the way it sounds. Now with regards to the MRVS, and please forgive me for my naivety, but if they don't operate correctly or have been maxed out how does this cause the engine to stall if the pressure I've recorded isn't far off? Sorry for what would appear stupid questions but am trying to figure out in my head this system works. Can't fix it till you know how it works right?!

Again, appreciate the input and looking forward to learning more.

Ben

the relief valve is 'balanced' with spring pressure essentially and if the relief pressure were say 180 bar, it would require in excess of that to allow the spring to compress and allow anything above that pressure to be dumped to tank;
when the pressure is relieved and dips below the 180 bar setting, it stops dumping pressure.

if the spring has been compressed to the point it is spring bound and is unable to travel / compress any further it's effectively a stop end and the excess pressure has no way to escape to tank.

with no where to go, pressure will overcome the capacity / power of the engine and stall it

basic set up of simple relief


there are also other much more complex systems with balanced RV cartridge set ups which rely on a given datum pressure to control them, using MUCH lighter springs.

if you go back to about end of August, last year, in my thread there's a lot about them in there

[Ben.Martins]

Hi v8druid,

This is great thank you and I will check out your post on relief valves. I guess my confusion is if the pressure I'm measuring at the valve block isn't far off from what it should be be, then the pressure doesn't have to be particularly high in order to stall the engine? Or where I'm measuring the deadhead pressure from not be a true system pressure? Sorry for all the question, just trying to understand!

Thanks again

Ben

[Muz]

Your revs are about right .. perhaps a little high but not much. Can you be more specific about what makes the engine stall ?

I'm looking for things like, engine at full revs, two main functions called to a stop, which will have their own reliefs like boom lift and dipper ram at the same time, or does just one of them do it ? Is there any black smoke at all on load ?

Can you post a picture of the engines dip stick ? ( trust me) is it a long dip stick about a foot, or a wee six incher ?

It may as well be a guvernor issue also, having established your working pressures and revs are good

[Ben.Martins]

The engine will stall when either lever is operated. So, will stall if bucket is used or dipper ram and then obviously when both are operated. Have added the picture although not a great one but you can see the dipstick beside the fuel pump. No black smoke either when put under load.

Have added a link to the video of when the engine cuts out.

Thanks Muz
Digger engine bay.jpg