Problem after HPFP replacement

So at 270kkm the HPFP on my 2.0TDI 125kw CAHA engine decided to fail, sending metal shavings through the whole fuel system. Ok, no problem sh*t happens, let's get the car running again. So I have replaced the HPFP, all 4 injectors, fuel rail, all with refurbished ones from a certified Bosch service in Germany. I have cleaned the fuel tank, the in tank fuel pump, fuel pump before the fuel filter and all fuel lines. Replaced the fuel filter, primed the fuel, and the car started without any problems.

When driving, car seemed to work fine, but once I hit anything over 2200rpm, the engine would stutter/lose power, and I would have to back of the throttle, let it get the rpm down slightly, and then it would work again, until reaching the 2200rpm mark again. Checked with VCDS, and there was a P0087 - low fuel pressure code stored. One of the injectors seemed very shaky and noisy compared to the others, so I first replaced that one but the problem persisted, but seem to have moved to different rpm range, around 3300rpm now. So next, I thought, the fuel regulator valve on rail, or fuel metering valve on HPFP might be bad, so I replaced both with brand new Bosch ones, but the problem is still there at around 3300-3500rpm, and I am slowly out of ideas.

Now it is not even throwing any code anymore, but is still stuttering. If I do not back of the throttle when this happens, the engine even dies (happened once, I didn't want to try it again). When logging with VCDS the requested fuel pressure, and actual fuel pressure seem to be spot on even when the problem happens, but to me it seems to be some kind of fuel shortage problem anyway?

Also when doing the fuel rail pressure test (https://www.youtube.com/watch?v=k50Z5JLfuJs), the pressure drops immediately after shutting down the engine. So does this mean the problem is definitely a leak somewhere either in the HPFP or on the injectors?

So I am guessing here what to check next:
1.Could it be the in tank fuel pump is going bad? When running it with VCDS it stops after a while with "Aborted for safety reasons" after about a minute of running.
2.Given that the fuel rail pressure drops as soon as the engine is stopped, could it be that the injectors are leaking or the replacement HPFP is bad?
3.Any other ideas are welcome


Sorry if this post is a bit "confusing" and all over the place, but it is late here, and I am sick of repairing the car so this was a quick write-up, I am going to attach some more information and VCDS loggs tomorrow when I am in a bit more sane state

Any help and ideas are much appreciated

Did you run the adaptation for the new injectors? the other thought is that you may have gotten a piece of trash in the seat of your HPFP check valve, I had it happen once to me, it caused a no run issue, but maybe your trash is just small enough to allow it to run kinda, I removed the top end of the HPFP and cleaned it good with solvent it has worked flawlessly for going on 100k miles.. as a note, I looked very close and used fresh paper towels, I never did see any foreign debris, but since it worked that's what I'm thinking.

Yes, I have entered the adaptation values for each injector. However I was unable to find a way to reset the Fuel Mean Value Adaptation (mentioned in notes here - http://wiki.ross-tech.com/wiki/index.php/2.0L_CR_TDI#Fuel_Pump). However as I understand some engines just do not have a way to do this? And as this is an early CR from 2008 I believe this is the case here?
As for the piece of thrash in the HPFP - I have been careful to watch out that everything was as clean as possible when puting stuff together, and as this is a refurbished unit from a certified Bosch service, I would like to avoid opening it for now if possible. But yes, I will definetly check this if I do not find any other fault soon

As far as the progress is - drove the car in the morning a bit, and got it to throw a P0299 - Boost Pressure Regulation: Control Range Not Reached code. But this sadly raised more questions than answers. As this is a family member car I wasn't driving it before, and I have no way of knowing if this was happening before the HPFP fail, as this person doesn't really push the car over 3000rpm very often. So now it is even possible that the problem isn't really fuel related, but maybe boost related, but I kind of find this hard to believe.

But I have visualy checked all boost hoses, and didn't find any leaks, also checked the vacuum system, and it seems to hold the vacuum all right, so no leaks there. The vane actuator on the turbo also moves without any problem when operated directly with vacuum pump. I also found that the intake manifold flap actuator is a possible cause for a P0299 code, but on this car the flap is contorled electrically so I have rulled this out.

So in the afternoon I took the car for a ride agian, to take some logs of boost pressure actual vs specified and high fuel pressure actual vs specified, and I got the P0088- Fuel Rail/System Pressure: Too High even before I actually started logging. So I cleared the code, and started logging, and the problem has not even appeared once I was doing pulls in 2nd and 3rd gear from the 1500rpm to the redline (about 5000rpm) and the car seemed to work flawlessly

I don't really know what to check next, but I have a few questions.

1. I did the fuel rail pressure test again after the afternoon ride when I was unable to reproduce the issue. When at idle the Fuel high pressure: actual value is around 250 000hPa which would be 250bar. Is this OK?
Then when I stop the engine and the pressure should slowly rise (as per https://www.youtube.com/watch?v=k50Z5JLfuJs this does apply to diesels as well?), it actually drops to about 3000hPa = 3bar. So this is a problem with a leak somwhere, be it either injectors or HPFP? Is there anything else I can check about this?

2. I unhooked both fuel lines that come into the HPFP and just inserted the key to initiate contact. I was sure that both in tank fuel pump and the fuel pump in front of the fuel filter shoud run in this case and send fuel to HPFP, but there was no fuel comming from any of the lines? Is this correct or should pumps run when contact is ON?

3.What are the tolerances for the "Injection amount deviation" for each injector? There is none shown in the UDS VCDS, and I have the information that OK tolerances are +/-3mg/str. Is this correct?

I can't seem to find a way to attach files here. I will just upload the logs somewhere and post links in the next post.

https://gofile.io/d/TXgU4R

Few logs are available here. It is just the fuel pressure ad idle, engine off, and a second gear pull from 1500-5000rpm, with boost and fuel values + injection deviation. This is from today, so this is NOT from the issue itself as I was unable to reproduce it today. I am just adding this, is it looks all right? It seems all fine to me, but I would appreciate another independent opinion.

VWALH said:

3.What are the tolerances for the "Injection amount deviation" for each injector? There is none shown in the UDS VCDS, and I have the information that OK tolerances are +/-3mg/str. Is this correct?

Click to expand...

Maybe this will help its my injection mg/str. I really don't know much about the tolerances yet Im just learning.

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Hi, I am sorry to post this only after two years, but better late than never right

So after a few more days diagnosing this issue, I came to a solution. The problem was the fuel overflow hose valve (the hose that comes from the injectors). It should hold 10bar pressure (as far as I can remember, not 100% sure that the number is correct), but the replacement one (brand new item, just not OEM one, but some other brand) that I have put on the car while repairing the HPFH failure, was apparently faulty and did not hold the specified fuel pressure in the overflow line, which caused the above mentioned issues. After replacing the whole overflow line + valve with new OEM unit, the car ran like new (and still does)

Again, sorry to post the solution after two years, but it still might come in handy for someone with a similar problem sometime in the future.

Hi just read your post and sadly looks like I'm facing same problem
Could you please confirm what sensor on the end cure the problem?
Much appreciated

VWALH said:

Hi, I am sorry to post this only after two years, but better late than never right

So after a few more days diagnosing this issue, I came to a solution. The problem was the fuel overflow hose valve (the hose that comes from the injectors). It should hold 10bar pressure (as far as I can remember, not 100% sure that the number is correct), but the replacement one (brand new item, just not OEM one, but some other brand) that I have put on the car while repairing the HPFH failure, was apparently faulty and did not hold the specified fuel pressure in the overflow line, which caused the above mentioned issues. After replacing the whole overflow line + valve with new OEM unit, the car ran like new (and still does)

Again, sorry to post the solution after two years, but it still might come in handy for someone with a similar problem sometime in the future.

Click to expand...

Hi just read your post and sadly looks like I'm facing same problem
Could you please confirm what sensor on the end cure the problem?
Much appreciated

It wasn't a sensor issue, but a fuel return line valve issue. If you google this part number "03L 130 235 K" you will see on pictures that there is a valve on the end of the return line, and this valve should hold a certain fuel pressure in the line (10 bar if I remember correctly). Well the replacement one that I bought (it was band new, to eliminate any possibility of metal shavings from old return line getting in the new injectors) was faulty, so I bought an OEM item at a local VW dealer, and that solved the issue.

VWALH said:

It wasn't a sensor issue, but a fuel return line valve issue. If you google this part number "03L 130 235 K" you will see on pictures that there is a valve on the end of the return line, and this valve should hold a certain fuel pressure in the line (10 bar if I remember correctly). Well the replacement one that I bought (it was band new, to eliminate any possibility of metal shavings from old return line getting in the new injectors) was faulty, so I bought an OEM item at a local VW dealer, and that solved the issue.

Click to expand...

Hello, good evening, Domingo called me and I am writing from Spain, I have a Seat Exeo with a 2.0 tdi 143cv CR engine. And I'm just looking for what can happen to my car, it has 170,000 km, maintenance up to date. Very preserved. But since I bought it in 2018 and 90,000 km, it always starts badly. Sometimes good, other times bad, regardless of whether it is stopped for a day or 5... I have verified that the rail pressure (with the engine stopped) is not stable, perhaps it rises to 3 bar or 5 bar and drops to 0.4, it rises to 1 etc... other times it is stable at 5.6 bar. Another test, with the engine started the rail pressure is correct 268 bar, but if I turn off the engine the pressure quickly drops to 5 bar...I have not yet changed any part of the entire pressure circuit.Forgive all the text, but I don't know where to start. Thank you