[T6_measured] Injector failure

[mmi]

Keyword “loud knocking metallic noise from engine”. VW has published in September a service note which can be found with vehicle's VIN.

The sound clips from my engine (150PS, EU6) with comments on 21 Oct 2017 in thread Tick over noise
EDIT: audio files from the thread copied here as attachments- Also the extracted plots at end of this post.

At time of the recording van had 16.000 km, now 32.000 km.

According to VW procedure the first step was to pour VW fuel additive into the tank and fill it up. The additive is widely used setane booster (2-ethylhexyl nitrate) which makes fuel ignite more easily/faster/stable. The additive is sold also as fuel system cleaner.



Second step was just to burn a tankful of fuel before measuring the injectors.

Step three, the measurement is simply to measure return flows of injectors when engine is idling and to compare fuel flows from injectors.

In the test three injectors failed well before the time was up, the remaining one was not on same scale with the others, so I would like to say that couldn’t verify if that one is working or just failing less. Anyways VW decided to replace all of them. The correct answer would have been no fuel at all in any measuring glass in 10 mins.

[EDIT:] for the actual allowed tolerances please check current engine workshop manual:

section 23 - Mixture preparation - injection​

paragraph 3.6 Checking return flow rate of injectors with engine running​

Delivery of the injectors took six weeks and they were just installed. Now only the time will tell if this knocking sound is gone.


PS. Actually the exactly same measurement was done already a year ago because of my complaints of excessive and strangely fluctuating fuel consumption. Then the injectors passed the test.
EDIT: The fluctuating fuel consumption seems to be just an illusion. Explained here --->

[T6_measured] Fickle fuel consumption on MFD – encore

In March 2020 finally got the long-awaited ECU (Engine Control Unit) software update. Unfortunately it took a while to get a good chance to do some measurements to try to figure out what has been changed. So finally a few weeks back dusted the VCDS and collected all kind of intriguing data. The...

www.t6forum.com

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Knocking sound - a recording vs. normal sound.

Recorded audiofiles which initiated the investigations as attachments.
Below also plots extracted from the audiofiles.
Engine CXFA (110kW/150BHP), DSG, 4Motion, MY16. Cold start (+2C), the knocking fades away after a few minutes.

Normal sound, full picture 0.270 sec, shadowed part 0.145 sec (=one cylinder stroke at 825 rpm).


Normal sound, full picture 1.6 sec, shadowed part 0.145 sec (=one cylinder stroke at 825 rpm).


Knocking sound, full picture 0.29 sec, shadowed part 0.145 sec (=one cylinder stroke at 825 rpm).


Knocking sound, full picture 1.6 sec, shadowed part 0.145 sec (=one cylinder stroke at 825 rpm).

Amplitude scales are not comparable because autoscaling sets the maximums to the top of pics but in this case proves that the disturbance is at rate of stroke of one cylinder. Basically engine firing (and/or valve rattle) can be seen even on these pictures even though the recorder (cell phone) was not that great.
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EDIT - similar issues:

https://www.t6forum.com/threads/less-than-3000-miles-2-new-injectors-needed.9237/

 

[Loz]

Very interesting and well done for sticking with it.

 

[Mooncat]

From your original sound clip, that knocking sound was most likely from a single cylinder (note that I didn't say injector!) so the usual way a diesel specialist would test this would be through a single cylinder cut off. If the sound went away on a particular cylinder, replacing the injector would be the next step. If the knock had gone with the new injector fitted, to verify the defective part, you would then re fit the original injector to make sure that the fault is associated with that part. (Obviously if the knock came back you would then refit the new injector again).

The test VW has done is for internal wear. If you had symptoms such as the engine cutting out at peak torque you would perform that test.

In normal circumstances for that amount of fuel being returned to the tank, I would say that your engine has been worked exceptionally hard, has had a tank of petrol by accident or some other issue with fuel lubricity. Fitting a tuning box or having a remap also reduces injector life but not to that severity. Your comment about excessive and fluctuating fuel consumption is interesting though. Did VW check the common rail pressure sensor and the MPROP when you had the original issue? If the engine has been running with excessive fuel pressure, you could have some cylinder and/or piston damage (this also gives a knock on the power stroke).

 

[mmi]

Thanks @Mooncat . Good points. Unfortunately the knocking was relatively rare event so there was no chance to swap things to isolate possibly failing ones. Actually the van never was knocking at dealer’s premises – they had it there standing quite some time and started it in the mornings and again in the afternoons – never happened there. So at the moment I can only be satisfied with these suspects being replaced. But I have to admit that this still bothers me because the root cause is unknown, and as you mentioned other possibilities still remain. I had pretty high expectations that fuel consumption would have stabilized but now after just a few runs on my “calibrated” test track I can’t see any improvement.

The engine has not been tuned or remapped. I’m the only driver and for all the fuel I have paid only price of diesel. When I bought this I had a thought to keep this 10+ years so I have been driving with care, not stressing it too much, hardly ever carrying anything heavy, minimal city driving, rarely less than 30 km drive – a dream job for a Transporter.

I’m confident that neither pressure sensor nor regulator were not inspected or measured, unless they did that so quickly that I didn’t notice. I think that any actual values from sensors were not even recorded with VW - just a check that no faults are present. When I had the first knocking noise just the faults codes (=none) were read next business day. I'll add these on the checklist.

My impression is that even in problematic cases there is no room or perhaps not necessarily competence for other experiments than what has been described in service notes. Obviously those give authorization for warranty work. Probably hard to believe but at the moment even the VW technician seems to be frustrated – he even mentioned that it would be a lot easier if something would just simply break.

What comes to noise described on 29 Oct 2017 in thread Anyone else got this funny noise? – this was not cure for that - the noise is still there. Main suspect now is flywheel…

 

[Mooncat]

I've just listened to your tick over noise again and I still think it is valve train. We have rockers with valve clearance compensators (fancy name for hydraulic tappet) and when these are not functioning correctly that is the sound they make. My 140 Euro 5 has done it a few times from a cold start up on a very cold morning but always clears once I start driving. I just see it as being a characteristic of engines with hydraulic tappets and don't worry about it. Only if it didn't clear I'd be into the dealership. It'll be interesting to see if the new injectors make a difference and I'm happy to be proved wrong if it was them.

Ref 'Anyone else with this funny noise' I found what the noise was in our Yeti. It's the dog cage in the back when the mrs leaves the drink bowl attached! It's strange why it sounded it was underneath the car but the noise is definitely that. Much cheaper to repair than a DMF!

 

[mmi]

Thanks again @Mooncat. A hydraulic tappet was prime suspect also at VW in the beginning. One of the reasons was that the knock never missed a beat. And, as you mentioned as soon as engine warms up the knocking is gone.

But as soon as the service note was published, VW linked my complaint to that. Anyways, it is good that at least something failing is now fixed – hopefully for good.

Before and after injector change we scoped out (with a good old stethoscope) engine all around, and recorded clearly distinguishable knocking sound at cylinder head. Unfortunately this noise is not gone by injector replacement. Sounds like a single hydraulic tappet and would have gone unnoticed without main episode. The sound not being hearable over normal engine noise would not probably alone be a reason for further actions.

Good to hear that you didn’t rush to replace the DMF!

 

[AndyStripes]

hi @mmi , did you ever get to the bottom of this noise please? I have a similar issue, injectors and cambelt tensioners replaced and it still doesn't make a difference. Here's a little youtube video of it....

It seemed to coincide with the front EGR pipe failing but that, and the egr itself have since been replaced. Any assistance would be really appreciated. 150bhp. T6. 2016. Manual. Best. Andy

 

[mmi]

hi @mmi , did you ever get to the bottom of this noise please?

Unfortunately not. The van was sold on in April-2018 (by a dealer) and didn't have any warranty (resale) issues.

 

[Kaph]

hi @mmi , did you ever get to the bottom of this noise please? I have a similar issue, injectors and cambelt tensioners replaced and it still doesn't make a difference. Here's a little youtube video of it....

It seemed to coincide with the front EGR pipe failing but that, and the egr itself have since been replaced. Any assistance would be really appreciated. 150bhp. T6. 2016. Manual. Best. Andy

have you found out anything about this problem?
i think i have the same noise in mine...

 

[AndyStripes]

have you found out anything about this problem?
i think i have the same noise in mine...

Yes, it was the fuel pump.

 

[Kaph]

Yes, it was the fuel pump.

Okey so you changed the high pressure pump? Did you find any trace of metal particles?

 

[AndyStripes]

Okey so you changed the high pressure pump? Did you find any trace of metal particles?

No particles. There were lots of reports of particles in new vans, but my bus has done 120k so put it down to natural wear and tear. From memory, I had a single piston pressure pump and they’re very difficult to source. We managed to get a reconditioned unit from somewhere in Southampton (opposite ikea). The way we finalised diagnosed the problem, was to just to gently squeeze the rubber fuel line, which cured the noise. Try the same trick maybe?

 

[Kaph]

No particles. There were lots of reports of particles in new vans, but my bus has done 120k so put it down to natural wear and tear. From memory, I had a single piston pressure pump and they’re very difficult to source. We managed to get a reconditioned unit from somewhere in Southampton (opposite ikea). The way we finalised diagnosed the problem, was to just to gently squeeze the rubber fuel line, which cured the noise. Try the same trick maybe?

Okey, i will try and see if i could Get any change in the noise. How long did you drive with the noise, just worried about the injectors if the pump fails before getting a new one.

 

[AndyStripes]

Okey, i will try and see if i could Get any change in the noise. How long did you drive with the noise, just worried about the injectors if the pump fails before getting a new one.

Crumbs, I think I drove like that for 2 months and a good 2000 miles. The engine and performance were never affected, if it wasn’t for the noise, I would never had known.

 

[Yappa Yappa]

Hi/Help,
We have owned a T4 Multivan TDI (ACV) for last 310,000 miles. Our only vehicle for the last 22 years. Now looking to move to a Euro 6 complaint T6 Caravelle. Agreed to buy a 2016 150PS manual 6 spd (47k miles) from a dealer and all was good until we went to final inspect & collect. The van drives nicely, but.... The engine had a very noticeable ticking noise. This was evident at drivers side of engine. We drove the vehicle and had it up to full temperature with brief 70mph on motorway before checking again and recording videos attached. Sounds very much like audio file attached above by mmi '....knocking noise'. Noise seemed worse at 1200rpm and engine seemed to run less smoothly, but could have been my imagination. We have been to see the vehicle previously and i did not notice this noise. In the interim, the dealer serviced the engine and did another couple of jobs. This should have included changing the fuel filter. Any further advice? Thinking of walking away, but 150PS/Manual 6 spd vehicles not very common and we like this one in many ways.
Would appreciate some help

 

[AndyStripes]

Quick way to diagnose is to pinch the rubber fuel pipe on top of the engine. The ticking will change or stop very quickly whilst the engine is still running, then it will stall. I had a reconditioned pump fitted but it still makes a slight tick and sounds like an old van now, so try to scope out a genuine new part if you or the dealer are going to repair. Garage 1 couldnt diagnose my problem, and garage 2 replaced the injectors and cam belt before realising the pump was at fault, so my bet is that your dealer is worried and has no idea how to fix. That should help your haggling!

 

[Yappa Yappa]

Thanks AndyStripes. Unfortunately it is a 6 hour round trip to the dealer, so cannot immediately do this test. If I do the test, does the engine stopping confirm that the fuel pump is the issue? The noise is very much evident on the drivers side of the engine, and not central or on the passenger side, which is where I believe the fuel pump is. I believe injectors are within a cavity beneath the intercooler. Not sure why the noise might be more evident on that drivers side?

 

[AndyStripes]

Yes fuel pump is on drivers side. It will sound like it's coming from the belt or near it. The engine will stall anyway if you squeeze the fuel pipe, but the pump is starved of fuel first so the tick sound will stop quickly and the rest of the engine is running for maybe 2 seconds after. So if you get 2 seconds of no ticking, then you've found the spot.

 

[Yappa Yappa]

Ok thank you AndyStripes, I think we are now in a better position to be able to understand and to respond to whatever the dealer comes up with as a proposal.

 

[Yappa Yappa]

The dealer is now talking about taking the van into the shop and removing the ribbed belt in order to try to pinpoint the noise. He is talking about the belt tensioner potentially being the issue. Noise is loud on the driver's side(=ribbed belt side) only. I have been trying to educate myself about the engine via SSP 564 and the injectors SSP465. So the engine is CXFA or CXHA Unfortunately i cannot be there for the test. Would it be worthwhile me asking them to capture a log of ECU and send this to me? Would this shed any light on injector or pump problems? other problems? what would i ask for? Sorry to be so ignorant, but what gets logged? everything? What time duration? Noise is there at tickover, but seemed worse at approx 1200rpm. Thank you