Volvo Penta V6-240 Fuel High Pressure Dropping to Zero

[Lpgc]

@Lpgc thank you for taking an interest in this issue, more eyes looking at a problem always help. You can look at the files if you want. Just go to rinda.com and click on the updates tab. Click the button next to Diacom and then click the download button. This will let you install Diacom software and you can view any .rec files. This is all free, if you want the extras like the service manuals and the harnesses to scan an engine, that costs extra.
Rinda taught me this when I was at a Very remote lake and the customer attempted to help me, but instead he knocked my laptop into the water. Customer used his satellite phone and downloaded Diacom to his Laptop and used my cables to finish the diagnosis and get him running again.

I would be very interested in your opinion.

Thanks, I will download Rinda and have a look at the files. I already attempted to look at the files by importing the data to a spreadsheet, doing that I can see a lot of the header and summary information but I didn't get as far as being able to read what I believe will be the live / realtime data in the files.



There has been talk about injector PWM not seeming to change much with engine load. I've converted DI engines to run on LPG using electronics which intercept the petrol injector PWM signal to calculate a PWM for LPG injectors. The petrol DI injectors can open and close much faster than LPG injectors and petrol DI injectors can be opened/closed several times during one induction cycle, the LPG injectors open/close much slower so the LPG ECU has to 'add up' the total pulse time of petrol injectors during a single induction cycle to calculate a total petrol injector pulse duration to base a single LPG injector pulse duration per intake cycle on.... If the PWM of petrol injectors doesn't seem to change much for different engine loads it may be partly because the petrol fuel dose depends on the pressure in the high pressure rail and partly because DI petrol injectors can be pulsed more than once per induction stroke (or even during the compression stroke) - The PWM pulse lengths might not change but if there are twice as many pulses there'd be twice as much fuel delivery if the high pressure rail stayed at the same pressure. The DI injectors might even do multiple pulses per induction cycle and individual pulses not be the same length, if they're not the same length live data readings might only show the average or longest pulse length, but even if individual pulses were the same length live data might not show total pulse length per induction stroke (total being pulse length X frequency per induction stroke). For a given rail pressure we'd expect 2 x 2ms pulses to deliver twice as much fuel (4ms total) as 1 x 2ms pulse (2ms total) but live data might show 2ms in both cases. In which case 1 x 3ms pulse (3ms total) would deliver 3ms total, but if we don't take account of number/frequency of pulses per cycle it would seem to us that the 3ms were delivering more fuel than the 2 x 2ms pulse when actually it's only delivering 3/4 of the 2x2ms (total 4ms) pulse. And this isn't even accounting for variable rail pressure. Interpreting how much fuel a DI system is delivering is complicated, especially if there's more than 1 pulse per cycle and live data doesn't reflect total pulse length per intake cycle... even before taking rail pressure into account. How much a given 'ideal' injector (ideal being open/close time not being affected by pressure) will flow depends on the square root of pressure x pulse time... Abstract (not including any unit terms) examples would be some random injector fed with 1000psi (square root close to 33) pulsed for 3ms delivers 99 'units' of fuel, the same injector fed with 2000psi (square root close to 45) pulsed for 3ms delivers 135 'units' of fuel, or the same injector fed with 2000psi pulsed for 2 ms delivers 90 'units'.

 

[Biz603]

I don't think shutting down an injector would give much useful info. I wouldn't know what to look for. But if you want to try I don't think it would cause problems and might be useful.
It's very unlikely the flexible fuel line is collapsing, but possible and would explain your issue. I don't know, but the auto people might might have a T that you could install by the HPFP. It would rule it out.

The PWM that I would like to see is the Fuel control solenoid.
Your injector pulse width operates a little different (but pretty close) then the other Volvo DI engines files that I have looked at.
This is different than all the other Marine engines that I worked on. All the other one's use pulse width heavily and you see big swings.
The DI engines have fuel pressure modulation so they change very little. If you watch the injector pulse width (IPW) you will see that it stays very constant until the event that your experiencing. This is slightly different from the other 4.3 DI files I have looked at. The .rec files I have from the correctly running engines that are 4.3 DI and they show the average IPW a little higher then yours until high fuel pressure reach's about 1800psi. Then IPW slowly rises to about 5ms. Your IPW stays very constant until the event and then it goes Waco then it goes up to almost cold starting IPW, this is different then other engines.

This brings up something. I haven't connected Diacom to a DI engine, so I'm not 100% sure what you see when you connect. But from helping others by looking at the .rec files and talking with them. There are sometimes many "monitors" that you can choose view/record. This is what some engines see.

View attachment 411948

I'm thinking that some (maybe all) of these might be useful in tracking down your problem. If you decide to do this as .rec files. It's important that they all be done one after the other with the engine already fully warmed up and try to make each .rec the same as possible. I suggest starting each one following this format. This is because when I look at them, I won't have to take the time to determine operating conditions as I switch between the different .rec files.

Stopped at idle, shift into gear, accelerate slowly (like 2 minutes) to reach full throttle (use the trim as you normally do), hold it there for 5 seconds and then slow down to neutral as you normally would. Repeat the next monitor.

It's possible the HPFP PWM might be covered in one of these monitors. From trying to help others I have found that some of them will have all these monitors and some will just have a few. One person had one monitor "grayed" out and couldn't access it. They called Diacom and were told that it was because Volvo hadn't enabled that monitor in the ECM and to talk to Volvo to get it reprogramed. They weren't a Volvo dealer and they found the problem without it, so I don't think they followed up.

This is very helpful. I do have several data sets as well. I'll record all I can using the test format you outlined. If I see the HPFP PWM I'll let you know.
BTW-I'm told from the Volvo Penta dealer that you can re-program most marine ECM's but not Volvo Penta. Or at least the one I have.

 

[Biz603]

I graphed the same data from your 18 min run.rec. What jumps out to me is your injector PW is flat under 1 ms through your acceleration to over 5000 rpm. It held close to 3ms until you started accelerating then dropped to 1ms.
Something seems wrong to me. Last summer when I was chasing poor performance and low power with @muc . my injector pulse width climbed with engine rpm to just under 5 ms at my under powered 4500 max rpm.
(Once I fixed the problem with new spark plugs the engine was back to full power and rpm. So unfortunately I didn't record healthy data.)
You are using significant power and fuel at 5000 rpm, but you injector pulse width doesn't reflect this. I'm thinking the readings from the
ECM are bad. I can't believe you're cruising at 5K rpm with idle speed injector pulse width.
It looks like your ECM was trying to compensate for the dropping rpms vs commanded power by opening up the injectors to 15ms to dump more fuel as the rail pressure was dropping.
Also interesting is as your engine was falling on its face the rail pressure briefly jumped back up to normal while the injector pulse width dropped back to a low level.
Observations, but no clue to the causes. This is a DIY forum and I hate to use the word "dealer", but is your engine still covered by the VP five year warranty? If it comes to it, ECMs are painfully expensive.

Great insight. Not sure this changes things, but I'm running it out of the water, the engine is under no load. When I do put it in the water I get the same results, but as you suggested, I might see higher IPW signals because the engine is under load.
Engine is 8 years old. I don't think there is still a warranty on it.
ECM is a 4-6 week delivery and $2,200. Yah, already asked just in case. Also talked with a dealer about swapping the ECM as a test, and they didn't have one to swap. Talked to a ECM repair shop, it's 3-4 weeks $850 IF they don't break it opening it up, then it's $2,200 for a new one anyways.
I'll get the .rec files up tonight.

 

[Biz603]

Ok. Got all the data. I'll post it in a separate post.
I didn't see the HPFP PWM so I recorded it on my oscilloscope. Vid coming.
The categories I had are:

 

[Biz603]

Here are all the data files. Each run with a engine start and slow RPM rise (over ~2 minutes) until failure. Then held the Throttle open as long as I dared as the engine would spit and sputter.

 

[Biz603]

Here is the video of the HPFP PWM signal. Measured at the HPFP connector.
You'll see as RPM increase the time base for the signal shrinks. This is what I would expect.
But I think the most important factor here is that you can hear the Engine start struggling, then, the HPFP PWM signal changes. Based on that, I think this signal looks good. Thoughts?
Also put a gauge on the low pressure fuel pump, again at the LPFP, it still stays between 70 and 80 psi. It does drop to 70 but after the engine starts having issues.
I still need to measure this at the HPFP side as was suggested before.

 

[Biz603]

BTW - I could run a test and shut down any injector I needed, but the engine would be limited to 2000 RPM, so I didn't try it.

 

[Biz603]

For reference, here is the engine system information.

 

[muc]

Great insight. Not sure this changes things, but I'm running it out of the water, the engine is under no load.

How many of these .rec files are under no load?

 

[harringtondav]

How many of these .rec files are under no load?

Also my question. I don't want to use the word 'worthless', but no load data comes close.

 

[Lpgc]

I downloaded the Diacom software and used it to look at the same section of .rec file @Biz603 posted a picture of in post #58 and @harringtondav referred to in post #60.

Derate1, derate2 and forced idle are not set during any of the file, so it seems nothing points to the ECU intentionally causing the engine to reduce power.

I expect the reason for rpm falling away while manifold pressure, engine load and injector pulse duration all rise will be because the engine suddenly starts to run lean... it cannot get enough fuel because the high pressure fuel rail pressure drops. I expect manifold pressure and engine load rise because the ECU calls for wider throttle to counter the drop in rpm, injector pulse duration rises in response to the combination of sudden drop in high pressure rail pressure and higher engine load due to the higher manifold pressure. Everything responding as expected except high pressure rail pressure.

The low and intermediate pressure rails feed the high pressure pump.. If pressures at the low and intermediate pressure stages remain normal throughout the period of the data recording (they are not shown in the rec file I've looked at, I don't know if there's even a sensor for them?) then the problem must be high pressure rail related. If the high pressure pump continues to receive an appropriate signal (PWM?) from the ECU then it must be the fault of the high pressure pump. If the ECU stops sending an appropriate signal to the high pressure pump then I'd expect it to be the ECU or the ECU's hpfp driver that's at fault.

IIrc @Biz603 measured the low and intermediate pressures and found they remained normal throughout?

Good ideas to check any piping between the low, medium and high pressure stages and to scope the signal to the hpfp.

 

[Biz603]

Also my question. I don't want to use the word 'worthless', but no load data comes close.

The boat is not in the water. In the .rec files the Engine Load data is all around 10%, until the problem happens, then it sores. I believe because it's calculated off other sensors that also sore because the ECM is trying to increase the actual RPM to the commanded RPM.

This might explain why the IPW stays low the entire way.

Back to not being in the water; I'm not near a body of water at the moment, but I can make that happen, if needed.

My thinking, and I've very open to ideas here . . .
1. If it's a fuel starvation issue, it will only happen sooner under load.
2. If it's the relief valve in the HPFP kicking out, then it should still happen under load.
3. If we get it back to working out of the water it should work in the water.

Does this effect how we look at the data, I'm sure it does. Perhaps I should have communicated this sooner.

What would we expect to see different in the water, besides I get some wind on my face? Ha.

 

[Biz603]

I downloaded the Diacom software and used it to look at the same section of .rec file @Biz603 posted a picture of in post #58 and @harringtondav referred to in post #60.

Derate1, derate2 and forced idle are not set during any of the file, so it seems nothing points to the ECU intentionally causing the engine to reduce power.

I expect the reason for rpm falling away while manifold pressure, engine load and injector pulse duration all rise will be because the engine suddenly starts to run lean... it cannot get enough fuel because the high pressure fuel rail pressure drops. I expect manifold pressure and engine load rise because the ECU calls for wider throttle to counter the drop in rpm, injector pulse duration rises in response to the combination of sudden drop in high pressure rail pressure and higher engine load due to the higher manifold pressure. Everything responding as expected except high pressure rail pressure.

The low and intermediate pressure rails feed the high pressure pump.. If pressures at the low and intermediate pressure stages remain normal throughout the period of the data recording (they are not shown in the rec file I've looked at, I don't know if there's even a sensor for them?) then the problem must be high pressure rail related. If the high pressure pump continues to receive an appropriate signal (PWM?) from the ECU then it must be the fault of the high pressure pump. If the ECU stops sending an appropriate signal to the high pressure pump then I'd expect it to be the ECU or the ECU's hpfp driver that's at fault.

IIrc @Biz603 measured the low and intermediate pressures and found they remained normal throughout?

Good ideas to check any piping between the low, medium and high pressure stages and to scope the signal to the hpfp.

Great thoughts. Some data points to respond to your questions:
Low and intermediate pressures stay in the normal range even when the high pressure drops. Intermediate stays at 70-80psi. Never drops below 70.
Help me out here, but it seems the measurements I took with the scope (see video above) look like the ECM is providing a good signal, and not dropping out before the engine fails (based on the sound of the engine failing before the signals on the scope drop off). I'm thinking this means the ECM output driver is working as well, but I could be wrong.
I'm on my third HPFP now. Same issue, all pumps. No pipes between the low and intermediate pumps. They are built as one unit with the fuel flow going through the case iron frame. And, I swapped this part out already, it's brand new.
Not trying to be a negative nanny here, just putting the facts out so we can all keep noodling on this.

 

[Biz603]

I appreciate everyone's input so far and I think we are close. I have to step away on a business trip. I'll be back 10/14. If you think of anything in the meantime, please let me know. Open to any suggestions or other things to try. I'll check back soon. Thanks again!!

 

[Lpgc]

Watched the scope video a few times, had to download a new codec to watch it, not sure what to make of it, seems to me the pulse frequency might drop off immediately when the rpms begin to fall off? But I suppose pulse frequency is rpm related anyway, in which case that would be expected and not the cause of the high pressure drop off.

You've said the intermediate pressure stays at 70/80, so it doesn't seem there's a problem at least as far as that.

I re-read your first post but I don't think you said whether the boat was new to you that has always had this problem in your ownership or used to run well in your ownership?

Struggling to think of something to suggest next. I know you've fitted several hpfp's with the same result... Are they the correct spec? Is there some sort of built in protection that could see them drop rail pressure if e.g. internal components overheat etc?

Hope to see you get this fixed on your return.