High Pressure Fuel Rail Leak Source

[BrokeBichB8]

Need help diagnosing the source of high pressure fuel rail leak. Had injectors ultrasonically cleaned and replaced hpfp as well as 034 hpfp piston. I use VCDS to monitor the pressure at the fuel rail and it drops rapidly when engine off and hot. I began trying to figure out because I am having hard starts when the car sits for 15 min+. I am wondering if there is any injector cleaning kit that allows hookup at the rail to test for leaks in injectors? Otherwise Im pretty certain I have no leaks in the Orings/lines themselves. I am just trying to diagnose if I actually have a bad injector somewhere or its an issue with my hpfp. Overall the car runs good but runs out of fuel up top on E40.

Any help diagnosing is appreciated as I am trying to not have to pull the blower and replace injectors unless I clearly have to.

[LowKeyLoki]

When you or your mechanic replaced the injectors did they replace the brass fittings on the hard fuel line under the SC running to HPFP? If not I’d replace those fittings before replacing an injector but you’d most likely smell the gas just under the SC. I’m more inclined to believe it’s a leaky injector and the gas is going into one of the cylinders, the hard to to start after it sitting is probably due to the fuel sitting in the cylinder causing a rich condition.

[sepheroth86]

I had a faint faint faint fuel smell with similar symptoms.

Took the blower off to find a lake of fuel under it. Replaced a damaged O ring and all is well.

[JRYtheS4]

When you or your mechanic replaced the injectors did they replace the brass fittings on the hard fuel line under the SC running to HPFP? If not I’d replace those fittings before replacing an injector but you’d most likely smell the gas just under the SC. I’m more inclined to believe it’s a leaky injector and the gas is going into one of the cylinders, the hard to to start after it sitting is probably due to the fuel sitting in the cylinder causing a rich condition.

I'd tend to agree with this assessment. Check your oil for smell of gas. Some of it will seep past the rings into the crankcase.

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[LowKeyLoki]

I'd tend to agree with this assessment. Check your oil for smell of gas. Some of it will seep past the rings into the crankcase.

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+1 on this
Definitely should fix this soon as gas will dilute your oil and reduce its lubrication properties.

[Fresh.S4]

When you or your mechanic replaced the injectors did they replace the brass fittings on the hard fuel line under the SC running to HPFP? If not I’d replace those fittings before replacing an injector but you’d most likely smell the gas just under the SC. I’m more inclined to believe it’s a leaky injector and the gas is going into one of the cylinders, the hard to to start after it sitting is probably due to the fuel sitting in the cylinder causing a rich condition.

why should you replace the hard lines?

if its a bad injector, im gonna make a big deal that its important to replace them, not clean them! their are internal screens that should be replaced AND most places that clean injectors do not pressurize them to operating numbers.

[BrokeBichB8]

When you or your mechanic replaced the injectors did they replace the brass fittings on the hard fuel line under the SC running to HPFP? If not I’d replace those fittings before replacing an injector but you’d most likely smell the gas just under the SC. I’m more inclined to believe it’s a leaky injector and the gas is going into one of the cylinders, the hard to to start after it sitting is probably due to the fuel sitting in the cylinder causing a rich condition.

I did not replace brass, I just replaced all seals on the injectors after cleaning them, teflon and o-ring. I agree with your assessment of fuel drip in cylinder that is staying stuck open, but I just want to be sure. I cleaned injectors the same time I did a budget carbon clean and hpfp swap with 034 piston.


There is zero gas smell in the oil I get the sentiment but I drive long enough every day (about 45Min ) that I figure it boils off if anything. I went through this whole fiasco with autotech and they were at least kind enough to give me a brand new hpfp oil/gas seal. There is also zero gas smell around the motor. Im really just kinda reaching out hoping if anyone can think of a way to determine what injector it could be. Fuel trims are not crazy out of spec but on one bank I do have some -% at idle so Im thinking it may be that.


and I replaced all the screens after cleaning the injectors as well! I was golden for a few weeks after, but I dont know what went awry :(

[LowKeyLoki]

why should you replace the hard lines?

if its a bad injector, im gonna make a big deal that its important to replace them, not clean them! their are internal screens that should be replaced AND most places that clean injectors do not pressurize them to operating numbers.

Not the hard lines themselves but the brass male to male fittings that screw into each rule rail and the HPFP. It's best practice to replace them from what I've read (and I believe it states so in the factory manual anytime removing the hard fuel line). They are brass and under high pressure so any small scratch or ding could cause a leak.

[JRYtheS4]

Yeah I mean gas is incredibly strong smelling so even a small leak under the charger you should smell if you stick your nose next to the throttle body. A little perplexing but I'd have to guess that something went wrong with the injectors.

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[LowKeyLoki]

Not sure what the best way of determining which injector could be the culprit, on a non direct engine you can usually pop the fuel rail off and and prime the system to determine which one in leaking. I'd try to log and figure out which cylinder bank it is occurring on and replace all three injectors on that bank, I think you are on the right track monitoring the fuel trims and other parameters like injector duty cycle, knock, misfires etc. Id perofrm a log for duty cycle on the injectors and see if anything sticks out first.

[Fresh.S4]

i knew my injector was going bad because it would only misfire at wot.
cruising around town and it never gave any issue. plugged in vcds and i could see in real time my misfire counter going off.

at first i thought i had the autotech problem too but no leaks or smells.
it was literally just a 50/50 chance that id get a misfire when i was on it (and rather embarrassing might i add when it happened lined up against other folks ) lmao.

finally did the injectors and when i found out how cheap they were through VW, thats when i started my campaign about everyone needing to swap them out. funny that just now over the last year, its becoming a thing now for everyone else when for years their was never talk about injectors failing.

[JRYtheS4]

i knew my injector was going bad because it would only misfire at wot.
cruising around town and it never gave any issue. plugged in vcds and i could see in real time my misfire counter going off.

at first i thought i had the autotech problem too but no leaks or smells.
it was literally just a 50/50 chance that id get a misfire when i was on it (and rather embarrassing might i add when it happened lined up against other folks ) lmao.

finally did the injectors and when i found out how cheap they were through VW, thats when i started my campaign about everyone needing to swap them out. funny that just now over the last year, its becoming a thing now for everyone else when for years their was never talk about injectors failing.

Injector pn?



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[LowKeyLoki]

http://https://www.audizine.com/foru...newer-revision

- - - Updated - - -

https://parts.z-vw.com/p/75727551/06E906036AL.html

[JRYtheS4]

http://https://www.audizine.com/foru...newer-revision

- - - Updated - - -

https://parts.z-vw.com/p/75727551/06E906036AL.html

Thanks. I think that's about what Audi charges for it too unfortunately.

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[LowKeyLoki]

Look around at different VW dealerships, local dealerships I’ve see them for under $200

[BrokeBichB8]

Thanks for the replies gang. I mean I guess I will have to just bite the bullet and pull injectors. I've been monitoring trims and injector duty but there isn't really much to go off of. I was thinking of going in VCDS hoping to trying to deactivate a cylinder and see if the trims went rich (unburnt extra fuel from the injector leak) but I don't think I know how to do that just yet.
A guy on the facebook group had only positives to say about the injectors from Rock Auto? Although at a $50 cheaper price im kind of convinced they're just super refurbished.
Also, I wouldn't mind changing those brass fittings as they alone are annoying but, you wouldn't have the P/N's by chance? Thanks

[LowKeyLoki]

https://www.audizine.com/forum/showt...-pics-and-tips

Optionally - gas line adapter fittings x2 07L127065A/06E127065B/06E127065D, see comments from theweebabyseamus

[BrokeBichB8]

https://www.audizine.com/forum/showt...-pics-and-tips

Optionally - gas line adapter fittings x2 07L127065A/06E127065B/06E127065D, see comments from theweebabyseamus

Do you guys know if 06E127065D will work? The 06E127065B doesn't even show as a listed part anymore on VW sites and the -D suffix part shows only to fit 2.0T versions. The -A part looks completely diffrent and has a rounded fitting tip vs angled?? thanks

[killer_s4]

Bought mine from here

https://www.vwdirectautoparts.com/oe...or-06e906036al