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Mk5 GTi stage 1 fuel pressure problems

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Lassebongo:
Hi!
Im new here so if the thread is posted in the wrong section let me know.

Ive got a 2008 Gti mk5 stage 1 with fuel pressure problems.
On hard pulls it jerks and in the VCDS logs the pressure drops from 110 bar to 7(with the new HPFP, the old one went up to 129 bar and dropped)
A local company loaned me a HPFP which is swapped but didnt solve the problem.
Fuel filter swapped last year.
The cam follower is also new, doublechecked and its in pristine condition.
There are no leaks from what i can see, atleast around the visible fuel rails and HPFP.

So whats left is the in tank pump and im pulling it out today but i dont know what to look for  :scared:

Could there be anything else causing this problem or can i just swap out the in tank pump and the problem should be solved ?
Can the in tank be repaired ?
Is a 4 bar pump enough?

ZoliWorks:
Check the part number of your old pump and buy based off of that. IIRC you need a 6 bar pump and a 6.6 bar filter.

Log the low pressure side with vcds next time you go for a drive so you can check what the pump is doing. Could be the pump, could be the controller or could be a worn out HPFP lobe. Even just a slight bit ow wear on th elobe can mess with the regulator open/close times and in turn mess up your fuel pressure.

Lassebongo:
Ty for the reply
I did the filter swap myself last year and did check the pressure requirements beforehand so the filter is the correct one.
Here are the logs:
https://log.tunezilla.com/s/bbQzxooI

I'm doing tests on the n80 today and checking if the charcoal canister is clogged because there is a hiss when opening the fuel cap.

How do I test the controller on the fuel tank lid?

ZoliWorks:
Holy, yeah look at your low-pressure side, that's basically dead. I'd say in-tank pump, controller or maybe the filter but unlikely. Your low pressure side is basically starving your engine completely. It should never really drop under 4.5 bar on full WOT.



Try logging the in-tank pump duty cycle as well. I forgot the exact VCDS param for it. Auxiliary fuel pump or electric fuel pump? something like that.

If you're going to replace it, there are a few threads here with people and the pumps they used.

Lassebongo:
Yea as I feared I ordered a new pump and controller. The new pump will have a newer revision, 1t0 DB i think it was, same with the controller. It's weird though because its a low milage for its age. 130k
Yea I did log the duty cycle att some point, lost the file, it did max out at 95% if I remember correctly.
Thanks for the insight, I'll post the results after the swap!

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