'FSI Fuel Rail Pressure' - Desperate

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Jeremy

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Hello everybody,

Newbie here, so apologies if this is posted in the wrong place. I have been scouring the threads to see if my problem has been covered. So, in desperation I am looking for any friendly advice. I am not a petrol head, so please excuse my ignorance.

For about 2 years I have had the joy of driving my 1.6Fsi it's been brilliant and a total pleasure to drive. This spring I started to get an intermittent loss of power. It was especially noticeable uphill. I have been to a number of German car specialists including my local Audi garage but not a single one diagnosed the issue. The performance has steadily worsened and I can no longer drive down the motorway safely as on any inclines the speed rapidly falls away (got overtaken by a horse box on my final drive). My friend has a similar model and he has VCDS and he ran some tests but was similarly puzzled see attached. His gut feeling is fuel lines/pump? I have a proboost fitted.

If anyone could point me in the right direction I would be most appreciative.

Jeremy
 

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i've had a few fsi's in the past but by no means an expert on them. Someone more knowledgeable then i will be along soon to steer you. wouldn't expect filter to be blocked so soon unless you'd had dodgey fuel. one fsi i bought had very low power until i changed the fuel filter then went fine. not sure if it had any fault code showing.
i had another fsi with the same fuel pressure regulation fault you have i think, and same massive power loss issues you are experiencing - never got to the bottom of the issue with that engine in my case - hopefully you have better luck.
one of the breakers on here may have a fuel pump, but best to wait for one of the FSI experts on a steer....
 
Audifan hello! This issue started after I filled the tank with low grade fuel from Esso! Very shortly after that I took it to a German car garage and they advised me to only use premium and that has been done ever since. So certainly for the last 8 months or so?
 
Good Evening Jeremy,

I am not a FSI expert.

I am pleased you enjoyed your FSI for two years before it started to go pear shaped this Spring, need to get it back to rights. Your experience with local garages is not surprising, few garages have the required expertise, after all the FSI was a novel now discontinued design 'before their time', why give themselves a headache for a car not worth much without a clear path to a solution and give themselves a poor name.

I agree with your friends gut feeling on fuel supply but alas the shown VCDS data gives little information.

The screenshot showing Block 140 is the way to go and out of interest the second field is the setpoint/target/specified fuel rail pressure by the ECU, 60 bar is normal, the third field is actual but the 3.8 bar is normal simply because the engine was not running and all to do with the low fuel pressure pump, I am sure Mac can comment, I have never got my head around it.

I suggest you seek more help from your friend and request two things.

1. They download the FSI specific lbl file to their computer, it will make VCDS diagnostics more readable and negate such explanations such as Block 140 above. The download is available here...

FSI ECU VCDS Label File Add-In Download

Attached something never before available to my knowledge¹, a VCDS label file for the FSI ECU in English. This file can be used with all versions of VCDS, Lite (Registered or Unregistered) or Full. Prior to this point the text that appears with FSI VCDS ECU Measuring and Basic Settings groups...
www.a2oc.net www.a2oc.net

2. Post screenshots of Block 140 data at an even 2500 rpm, 3500 rpm and 4500 rpm.

Hopefully this may reveal something.

Just trying to help.

Andy
 
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I had this problem….
Firstly…. you said you used low grade fuel - remove the fuel and put the correct grade in👍

I had this problem- turned out to be fuel filter, had not been changed for 8 years (I had, had car for less than 12 months) so had it serviced with new filters and new plugs etc - no change😢

The filter had disintegrated consequently, all filter debris had gone everywhere so had all fuel lines cleaned out - no change😢

Next step was to have HPFP removed and stripped - this was the problem, rubber rings inside had started to disintegrate and causing blockage ….. had replacement from A2Steve and once fitted car was back to normal 😍
 
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There does seem to be a general agreement that fuel is the problem, and I'm not going to disagree. Replacing the fuel filter would is sensible, and if you could get that done first, then do so, before the scan, if possible, to rule it out.
(Here's a link to a post with a picture: https://www.a2oc.net/community/inde...our-fuel-filter-petrol-cars.35363/post-309364 ).

@Andrew is right, the fuel pressure in the scan is as it should be, with the engine not running. The FSI has two fuel pumps, an electric pump in the tank, which runs when the ignition is turned on, and that's the pressure you see in Group 140, Block 03, and so your electric pump is OK.
This electric pump feeds the second, engine driven pump that generates the high pressure to the injectors, and it's this that is suspect.
Follow Andy’s advice, and hopefully your friend with VCDS can install the lbl file, then monitor G140, B02 & B03, first, as you've done, with the ignition on, but engine not running, then start the engine, to see what pressure is present.
Block 02 is the pressure the ECU has requested, (Spec), and Block 03 is what the fuel pump is actually delivering. (Actual).
At idle, the Actual and Spec pressures should be around 60 Bar, and increase to around 100 Bar at 2,500 rpm.
Let us know what you see, and we'll go from there. I think it'll give us a good idea of what up with your FSI.
Here's a screen shot with the FSI specific .lbl file, courtesy of @Andrew. The text above each measuring blocks is correct, not the misleading nonsense that is seen without the new .lbl file.
Good luck.
Mac.
1699088622227.png
 
Fuel is critical on the FSI. It must ONLY be run on premium 98/99 octane fuel. It is NOT compatible with E10 fuel as that will damage fuel system components. That also rules out lower grade fuel and octane boosters as the base fuel is still E10. Who knows how often the wrong fuel has been used by previous owners, my guess is most of the time!

The system has had E10 so replace the fuel filter regardless and follow the information / instructions given by others regarding the scan and HPFP.


Good luck.
 
Gentlemen, Thanks for the comments, very interesting.

I'm off to get a filter now and will conduct before and after tests and revert back. Really appreciate your help.
 
Good evening!

With the generous advice offered earlier including, changing the fuel filter, now complete, I thought I would share the following information. It a series of screen shots both before and after recorded via VCDS. In truth, it means little to me, so any clarity or guidance would be very welcome?

Jeremy
 

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Good Evening Jeremy,

Thank you for the prompt response and screenshots of Group 140 at various revs. I am puzzled, not what I was expecting but that will be my ignorance, as I said I am not an expert. I did not expect the actual fuel rail pressure to remain at 3.8 bar, but that will be do with 0% load, which I take to mean you were stationary, something I overlooked, sorry.

I will perform the same exercise with my FSI and take screenshots for comparison with yours. I am busy today (Sunday) so it will be Monday unless Mac wants to post today likewise his FSI behaviour when stationary. Always good to build up the knowledge of data values.

Back this evening.

Andy
 
PlasticMac said:
Just a had quick look, and the only odd one out, (unless I'm missing something, quite possible), is the after filter change, engine not running, which shows no pressure set by the ECU, and the electric pump, apparently, not running. Can only guess it's something to do with the line draining during the filter change.
Once the engine runs, all is well, pressures as expected.
Very similar to the pressures before the filter change, so fuel pressure doesn't seem to be the cause of the power loss.
I should have asked for a Fault Code scan of the engine controller in my first post. It should have been, and usually is, the first thing I say!
So that has to be the next move.
Perform an Auto Scan, (all controllers), with VCDS, just to get a clear picture of the car.
If you open notepad before you start, then, at the end of the scan, click on "Copy Result" (or could be "Copy Report"), button, and paste the text into notepad, and save.
Next, clear all faults.
(Depending on the version of VCDS, you may have a single Clear DTCs button, - full version), which clears them in one go, or you may need to go into each controller, (Lite version), and clear them one controller at a time).
There should be a clue in the scan results, probably in the engine section, to what is up.
If the DTCs have not been cleared before, then you'll get loads of codes, don't worry, most of them will be historical, and no longer present, but the clue will be in there. A rescan will confirm they are cleared. To get only the codes associated with your power loss, you'll need to go for a drive, and induce the symptoms, so fresh codes are logged.
I'm thinking the engine is going into limp mode, at high engine loads.
Please encourage your VCDS provider to install the new lbl file, if at all possible.
Good luck,I'm sure we'll sort it.
Mac.
Edit: If the ECU detects a condition that triggers Limp Mode, the ECU does this by reducing the Fuel Rail Pressure, so Limp Mode will give the same symptoms as low fuel pressure. It would normally cause the EML to illuminate.
Do you see the EML, at first turn of the ignition key, (all dash lamps test), and do all dash lamps go out, when engine starts?
Mac.
Click to expand...
Yes, after these tests my friend cleared all warnings and the EML was illuminated on turning the key and subsequently went off! However, after a wee bit on driving home it then came back on!
 
Jeremy said:
Yes, after these tests my friend cleared all warnings and the EML was illuminated on turning the key and subsequently went off! However, after a wee bit on driving home it then came back on!
Click to expand...
OK, we need to know the DTC associated with the EML. So another scan please.
Very good chance that it'll point towards a diagnosis.
Mac.
 
Good Evening Jeremy,

As promised I have today collected some VCDS data of my FSI for comparison with your FSI, focussing on Group 140 and high pressure fuel delivery.

From the onset I have to say I am bewildered, nothing is making sense, I suspect I have misinterpreted the exact state under which you took your data.

To start at the beginning. Note my data was collected after a good run to do shopping, the engine was thus well up to temperature.

First comparison, engine off and ignition on (and stationary!).

Mine.

1699301939176.png


Yours before filter change.

1699302087311.png



You have included engine off after filter change but unfortunately 'Go' was not clicked and thus no information so I have not included.

Initial observation, wildly different fuel rail pressures.

Moving on, second comparison, our engines idling (and stationary!)

Mine.

1699303361417.png


Yours idling, before and after filter change, (identical?)

1699304334962.png


1699304378489.png


The startling observation is your high pressure fuel rail only has low pressure.

Last comparison for this evening with more revs. Apologies I messed up, I was trying to match yours at 2500 rpm but I got into a knot taking the screenshot and by the time I sorted it my revs had halved, only noticed when home.

Mine at more revs.

1699305347060.png


Yours at 2500 rpm after filter change.

1699305465731.png


Again, there is no high pressure on yours?????!!!!!.

Something is badly wrong, my understanding is flawed, wrong assumptions, on top I find it incredulous you can drive anywhere on just low pressure.

Lastly a possible important point. Notice on my last screenshot of Group 140, Block 4 has changed to 'System OK' whereas yours remains 'TEST OFF'. I do not claim to understand this except by the text mine is happy.

I also took a log of Group 140 driving, but that will have to be tomorrow now and my concluding thoughts.

Andy
 
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