Volvo EC20 Engine stall under load

[Mattir]

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

Mitsubishi L3e max rev. around 3100 rpm.

the engine in your video sounds pretty much the same as my 15b.

[Muz]

Mitsubishi L3e max rev. around 3100 rpm.

Due to fuel efficiency and torque curve, you wouldn't expect an engine in an excavator application to be set at that though ... 2.5 would be about right.

[Muz]

Looks like the operator is moving the slew lever at the same time as bucket close ? .. Anyway the stall is quite evident. I wonder if someone has physically removed the relief valves ?

[v8druid]

Looks like the operator is moving the slew lever at the same time as bucket close ? .. Anyway the stall is quite evident. I wonder if someone has physically removed the relief valves ?

Or wound 'em down solid so's they're spring bound ...... as you say, aside from the MRV each circuit should have an RV ..... and if they fail / don't function, the MRV should kick in a few bar above the individual ones ...... unless ...... someone's been tampering

The OP needs to be tee-ing into each circuit, with a gauge, to see what they max at, when it stalls

[Ben.Martins]

Hi Guys,

Bit of an update. So, I've pulled some more data from this digger. I got someone to demonstrate a couple of bits of kit from Pico and they now have a pressure transducer that connects to the Minimess ports. So now I can see both RPM and pressure which is interesting! This is how it was setup...Valve block.jpg

So the red line in the picture below is taken the reading from this position. Am I right in thinking that if the MRV is held shut there will be a significant increase in pressure in order to stall the engine? It's just the pressure I'm measuring is around 180 BAR when the engine stalls or could that be enough? I have managed to clean off the MRV at this end of the valve block and it has all the tell tale signs of being adjusted at some time, or in this case, rounded out!

DIgger with pressure.jpg

I've found the valve out a few turns and now the engine no longer stalls but I'm not sure how well it will perform when being operated. I've asked the operator to let me know when he is going to use it next so I can attend and observe. Is there a possibility that there was piece of dirt lodged in the MRV or it was sticking or wound all the way in, which would cause it to not release then pressure? Am also curious by the spike in pressure once the engine has turned off, any ideas?

Sorry guys so many questions I know, I'm just a little too keen I guess!!

Thanks again for your patience with a newbie!

Ben

[v8druid]

Hi Guys,

Bit of an update. So, I've pulled some more data from this digger. I got someone to demonstrate a couple of bits of kit from Pico and they now have a pressure transducer that connects to the Minimess ports. So now I can see both RPM and pressure which is interesting! This is how it was setup...[ATTACH=CONFIG]3865[/ATTACH]

So the red line in the picture below is taken the reading from this position. Am I right in thinking that if the MRV is held shut there will be a significant increase in pressure in order to stall the engine? It's just the pressure I'm measuring is around 180 BAR when the engine stalls or could that be enough? I have managed to clean off the MRV at this end of the valve block and it has all the tell tale signs of being adjusted at some time, or in this case, rounded out!

[ATTACH=CONFIG]3864[/ATTACH]

I've found the valve out a few turns and now the engine no longer stalls but I'm not sure how well it will perform when being operated. I've asked the operator to let me know when he is going to use it next so I can attend and observe. Is there a possibility that there was piece of dirt lodged in the MRV or it was sticking or wound all the way in, which would cause it to not release then pressure? Am also curious by the spike in pressure once the engine has turned off, any ideas?

Sorry guys so many questions I know, I'm just a little too keen I guess!!

Thanks again for your patience with a newbie!

Ben

If the MRV is wound in solid, it effectively dead ends the circuit and any excess oil has no where to go, so the motor stalls - it's inevitable, if all the individual circuit RVs have also fallen foul of whatever idiot wound the MRV in solid.

180 bar may be the pump's max capability ? Muz??

the RV may well have a capacity greater than this .....before it becomes spring bound, by winding it shut, so outing it a few turns may well still be within satisfactory limits AND will allow any excess pressure / oil somewhere to release to.

As I said before, you really need to be tee-ing into individual lines to see what pressures you are getting in each circuit .... especially now if it's dumping through the MRV at below working pressure.


You also need to be investigating all the individual RVs as they should dump before the MRV which is a fail safe measure, if all else fails.

The MRV needs setting up as it should be and then all the individual circuit's RVs set up in a similar manner (usually a few bar below the MRV)

As for the spike, that IMHDO is the resultant pressure achieved as, that poor little motor ramps its guts up against a solid wall of oil and expires

Bet that transducer's expensive ..... I like a good old gauge, but can see the advantages of an electronic record of what's occurring .... I'm just a Luddite on the 'puter front

[Muz]

Interesting bit of analytical stuff there As to the spike after shut down .. could be a number of things, IIRC that unit has a variable displacement pump, and not the gear type found in smaller models. These systems use a special valve on the pump to force the swash plate to zero delivery after shut down, so that, the engine cannot be loaded hydraulically on startup, which would make starting impossible or difficult ... so it might be related to that .. also your guvernor settings have been tampered with, because the brass bell covering the tensioner adjustment is missing so its likely that will be wrong too, meaning the engine is not providing enough grunt when its loaded, you say there was no smoke when shut down, so I suspect this is an additional issue

[Mattir]

Due to fuel efficiency and torque curve, you wouldn't expect an engine in an excavator application to be set at that though ... 2.5 would be about right.

Yes. The 3100 was taken from curve, but might not be applicable in excavator use as you say.

[Mattir]

Interesting stuff.

Seems that the pump+engine is capable of delivering up to 237 bars until it stalls. That is quite well in line with my -15b. I have measured it and the MRV is set on 200 bars (yes I know it's a bit highish) but runs well even though sometimes hear the engine revs drop under heavy load. I quess that the 170bar set value would be good for longer life time.

Support V8Druid's theory.

[Muz]

180 bar may be the pump's max capability ? Muz??

will be higher than that, but how its reflected in the circuit is not so simple

[v8druid]

Interesting bit of analytical stuff there As to the spike after shut down .. could be a number of things, IIRC that unit has a variable displacement pump, and not the gear type found in smaller models. These systems use a special valve on the pump to force the swash plate to zero delivery after shut down, so that, the engine cannot be loaded hydraulically on startup, which would make starting impossible or difficult ... so it might be related to that .. also your guvernor settings have been tampered with, because the brass bell covering the tensioner adjustment is missing so its likely that will be wrong too, meaning the engine is not providing enough grunt when its loaded, you say there was no smoke when shut down, so I suspect this is an additional issue

the swash is usually kept closed/down stroked by a gert spring ....this is overcome, to upstroke the pump, by oil pressure, usually from the load sensing line ... so on start up, with no oil pressure in the system the pump is down-stroked completely. Once up and running the pump's valve-age will build up the delta pressure to whatever it's set to (50 bar on the 'Drema - more usually 30-ish bar, apparently on most kit) before the main swash pump will develop any pressure, other than whatever delta is set to.

Any abrupt interruption in the systems, especially at the pump, like a stall, will cause all pressure to dump to tank, via the pump's control systems/valves once it has stopped rotating and reset to start mode.

[v8druid]

will be higher than that, but how its reflected in the circuit is not so simple

best points to measure it are the Load Sensing line to the pump's valve-age and straight out the pump, say where it feeds a breaker line, before the breaker valve, but remember to add on the delta pressure to whatever reading you get, for a true figure!!

[Ben.Martins]

Thanks Guys,

This is all really useful and I really appreciate your assistance. I have a little update. After looking more closely at the MRV it would indeed appear that it has been tampered with at some point in it's life. The Allen key part used for adjusted had been rounded out. Using the live stream from the PicoScope, I reduced the pressure so not much happened and the engine obviously didn't cut out. I then gradually wound it back in until both pressures when deadheaded were the same. Now the engine doesn't cut out! I would love to say success but I'm not yet convinced at the moment. Am not sure if I could have even released a sticking valve just by moving it but the fault may occur again in the future. Think there is more going on with this one than meets the eye! I'd love to test this more thoroughly but for the minute the operator wants to use to see how it goes. Thanks for the input guys and as I've said I really do appreciate your time and expertise. If I hear anything back, good or bad, I will let you know.

Thanks again,

Kind regards

Ben

[Muz]

Think there is more going on with this one than meets the eye!

Correct

see here post #22

... .. also your guvernor settings have been tampered with, because the brass bell covering the tensioner adjustment is missing so its likely that will be wrong too,

As V8 suggested .. you need to set the correct pressure 'in line' for the relief to blow, then have all of them set that way so that when you pull on main services 'together' to end stroke, which are usually boom lift, dipper in/out and dozer blade up usually , it doesen't kill the engine whilst at full revs, yes it will labour heavily but it shouldn't kill it.

Some diggers are different, but those should be the three main loads on your hydraulics on mini Volvo's .. Ive never owned an EC 20 though .. every other one from that era but not that one, so I dont know how its valve block is wired but most follow those similar rules

[Ben.Martins]

Correct

see here post #22

Indeed Muz, I'll get back to it and double check what's going on with this. Think this needs a bit of a complete overhaul to be honest and as with everything the operator is reluctant to spend more money on it. I may just say I'll look at it in my own time to gain more experience.

Thanks again for your input.

Ben