Intermittent hard or no start on 4.0T S6 S7 RS7- possibly solved

[qcrazy]

Thanks for the update. How many miles on your car?

[MrTorres]

I believe my hpfp is leaking. Where do they tend to leak? If I did the autotech upgrade and replaced the orings would that stop the leak? Or is the leak caused by mechanical damage to the cam follower or something else? Tia for any responses.

[Hofahome]

Update: I followed the diagnosis criteria via the TSB, and verified the hpfp's to be the issue. I just installed the hpfp's and everything works great! Thanks to everyone on this thread, couldn't have fixed it without yall!

Tracking this issue down was a PITA for me so I am glad to help others.


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[Woodepic]

Thanks for the update. How many miles on your car?

about 77k (though it's been stage 3 APR since about 70k)

[Woodepic]

I believe my hpfp is leaking. Where do they tend to leak? If I did the autotech upgrade and replaced the orings would that stop the leak? Or is the leak caused by mechanical damage to the cam follower or something else? Tia for any responses.

Not sure where the exact leak location is, but it wasn't due to cam follower damage. I took mine out while doing the fix and it looked great.

[Woodepic]

Update: I followed the diagnosis criteria via the TSB, and verified the hpfp's to be the issue. I just installed the hpfp's and everything works great! Thanks to everyone on this thread, couldn't have fixed it without yall!

Another update:

The issue has actually started to come back about 2 weeks after the fix, albeit not nearly as bad *yet*. When I swapped HPFPs, the car worked perfectly, but now it's slowly degraded. (only been about 5k miles on new HPFPs).
It's worth noting my car is running APR stage 3 with 94 octane E10 fuel, and has been for about 7k miles. Is it possible that since my HPFPs are working double overtime (making about 650hp), that this prematurely wore them out. However, I did initially have this issue before tuning the car.

It's worth noting that audi has gone through 5 revisions of this HPFP (oldest to newest):
079127025T
079127025AE
079127025AH
079127025AK
079127025AJ

My car (before the tune) was using the K variant, aka the first one ever made. I assume that due to leaks (from normal, non-tuned cars), they updated it. I replaced my pumps with Hitachi HPP0023's which cross reference to the latest AJ variant. (Hitachi is audi's oem supplier).

So here's the possible scenarios:
- The K variant was so bad that it broke even with stock cars. The AJ variant is improved enough for it to work without issue on a stock car, but not when tuned.
- The K variant was so bad that it broke even with stock cars. The AJ variant is also bad, and would've broke anyways, even on a stock car, hence why it's broken on mine.
- The AJ variant is good enough even for a tuned car, but now my Injectors are also leaking?

One potential bandaid fix I may try is getting the dealer to update the ECM with SVM Code 01A225. (This is reportedly the fix as per TSB 2046724/7). I assume this software change prevents the intake from being exposed to crankcase fumes after turning off the car. This way when you go to start it, it won't be full of gasoline vapours, making it either run rich or not start at all. My concern is that fuel vapours are still in the crankcase, which means something is leaking.

[qcrazy]

Are you sure you are running the correct HPFP for your tune?

APR runs a different HPFP with a larger bore. This changes the calibration in the tune, as each stroke would be expected to provide more fuel. Is your APR tune set up to use their HPFP?

It could be as simple as the wrong pump. Unfortunately, the Gen III pump from APR is $$pendy.

[Woodepic]

Are you sure that Gen3 APR pump is intended for the 4.0T? I've only seen it suggested for the 2.0T. In this thread, Arin suggests the Gen3 may work, but it's unclear. Before I bought new HPFPs I reached out to APR support to ask if there was any specific HPFP I should buy for a stage 3 setup. TLDR: they said go for the oem pump. Full email below:

sc.jpg

Also it's worth noting, I'm not having any issues regarding getting enough fuel, or making enough power. In fact, my car now has a 2.9s 0-60 lol. The issue is just longevity (if HPFPs is even the issue).

[qcrazy]

I bought an APR Bi-pipe 20 years ago and I haven't purchased another APR product since. Just throwing out an idea as the B9 S4's are all currently working through HPFP selection and tuning, so it was fresh in my mind.

If this was an issue for you, the car could accommodate with fuel trims so it may run fine. APR technically said you should contact your dealer and verify which software version you had flashed. May not be it, just throwing out an idea.

FWIW, this pump lists the 4.0T.

[Woodepic]

Okay thanks for the thoughts! Regarding software, I believe Levi (in the email) was referring to a previous email where I also asked about updating the software as per the TSB. I'm now really curious what that software update does exactly

[yoo_gabriel]

I'm currently having hard start issue for about a month now, is it possible to upgrade the HPFP with autotech HPFP, or would I just have to replace the whole thing with part # 079127025AJ
Thanks

[ANMS4]

Check the injectors. I just went through this, two new HPFP’s and changed nothing! Had two injectors leaking when the car was off/asleep

[brad281]

Check the injectors. I just went through this, two new HPFP’s and changed nothing! Had two injectors leaking when the car was off/asleep

Engine out repair? Ouch.

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[ANMS4]

Engine out repair? Ouch.

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No thank god LOL, Just remove the SC , still costly $860

[brad281]

No thank god LOL, Just remove the SC , still costly $860

Different story on the 3.0T. The 4.0T has the injectors on the outside of the V. You have to take the engine out.

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[dtdeg]

Figured I would post up here in case more people start having this issue (or still are without resolve). I have gone back to stock and my car runs fine ~85% of the time, however, the tune was not the issue, it was just making the issue worse. The car was running so rich due to the alteration from the tune that the car was maxed out on how much fuel it could pull. Now it runs, but it still has hard starts when warm sometimes and runs rich too much, but usually the rich aspect is only at idle or when off-throttle.

I did find the cause of what causes the hard-starts, at least in my case (see attachments). Basically, whatever the root cause is is causing the high-pressure to build-up so high, with the car off, that when you crank the motor you flood it out. Take a look at the three log snips I attached and you will see the high-pressure is way too high and these are with the car off! I have plenty of logs showing that these high pressures are not normal and the hard-starts only happen when this pressure build-up occurs. The log with the blue horizontal highlight is right when the motor died.

If you want to log what I am logging, use the variables below.

IDE00148
IDE00186
IDE00188
IDE00201
IDE00202
IDE00559
IDE00565
IDE00597
IDE00598
IDE00604
IDE00605
IDE01869

I've noticed the same exact thing with the fuel pressure being way to high like yours. Normaily it wil not rise any further then like 8MPA +/-. Did you find the root cause?

[Optimus247]

(Just a side note)

After my APR stage 1 tune ... I went for a week long drive in the mountains of NC ...

At an upper elevation ... I had a no start scenario ... I was freaking out ... push the start button ... turning over ... No Start ... I panicked a little ... but, I had an idea to pump the throttle as it was turning over ... viola ...!! it started up, with a very low idle ... had to keep pumping the gas pedal ... till it got over the low idle ... next mountain over ... same thing and pumped the gas pedal during the start ... and till the idle came up ...

Back at home in the low lands ... no issue since ...

[gk1]

(Just a side note)

After my APR stage 1 tune ... I went for a week long drive in the mountains of NC ...

At an upper elevation ... I had a no start scenario ... I was freaking out ... push the start button ... turning over ... No Start ... I panicked a little ... but, I had an idea to pump the throttle as it was turning over ... viola ...!! it started up, with a very low idle ... had to keep pumping the gas pedal ... till it got over the low idle ... next mountain over ... same thing and pumped the gas pedal during the start ... and till the idle came up ...

Back at home in the low lands ... no issue since ...

That is weird I moved from sea level to 6500 ft and have no issues like that.

[dtdeg]

is it possible for someone to give a log of a fixed scenario . im currently doing diagnostic on my car per tsb but not sure if my hfpf are faling. everyone's experience is that the hard start needs more time then the tsb describes.. like myself. problems starting after 30 min +. Hope someone can upload a log of the 3 sensors (IDE00186 IDE00188 IDE06212) so i can do a compare of a warm engine shut off cooling period.

[qcrazy]

2014 S6, just shy of 97k miles...add me to the list.

It didn't want to start while running errands, finally got it going. Two new HPFP's and it is starting better than it has in as long as I can remember. I think it had been leaking for a while.

I pulled the pumps apart, looks like it was the passenger side. I am getting data and pictures to make a longer post here in a few weeks. But for now, add me to the list...

[brad281]

Same here. Had been dealing with the hard start issue for a couple years in a 2013 S6. It wasn't a huge inconvenience early on, but started getting worse, so I replaced the HPFP's. Been fine ever since. Going on 2 months now.

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[dtdeg]

is it possible for someone to give a log of a fixed scenario . im currently doing diagnostic on my car per tsb but not sure if my hfpf are faling. everyone's experience is that the hard start needs more time then the tsb describes.. like myself. problems starting after 30 min +. Hope someone can upload a log of the 3 sensors (IDE00186 IDE00188 IDE06212) so i can do a compare of a warm engine shut off cooling period.

For me the fix was also replacing both hpfp.

[dab]

My rs7 if I let the fuel get too low will do the hard, no start for a few weeks.

[Botbasher]

Two new HPFP's and it is starting better than it has in as long as I can remember. I think it had been leaking for a while.

Q...

What is "better"? My 2.0tfsi usually takes a couple cranks to start... sometimes it's nearly instant... sometimes it's a couple cranks. I've had multiple HPFP pumps (AutoTech issues), new S3 injectors and a ton of other work and it's always done about the same (after timing chains).

The 4.0 seems to mimic that pattern (no timing issues) of randomly taking a couple extra cranks to kick in, but ALWAYS to a smooth idle.

Is there a spec for the cranking that one can look at to start and determine when/if problems are happening? My 14 S6 has just crossed 106k so I am either really lucky or it's had a lot of this corrected already (bought at 103k).

Cheers,

Ken

[qcrazy]

Q...

What is "better"? My 2.0tfsi usually takes a couple cranks to start... sometimes it's nearly instant... sometimes it's a couple cranks. I've had multiple HPFP pumps (AutoTech issues), new S3 injectors and a ton of other work and it's always done about the same (after timing chains).

The 4.0 seems to mimic that pattern (no timing issues) of randomly taking a couple extra cranks to kick in, but ALWAYS to a smooth idle.

Is there a spec for the cranking that one can look at to start and determine when/if problems are happening? My 14 S6 has just crossed 106k so I am either really lucky or it's had a lot of this corrected already (bought at 103k).

Cheers,

Ken

For me, it wasn't the "cranks" for it to start, it was after it went to start. Prior to any issues it would start and go to a smooth stable idle.

Then suddenly in late November, shortly before I put the car in storage, it started and suddenly died once (cold start). Not a big deal, started fine on the second try. BUT after that one instance, when I started the car it would start up...then the idle would drop down...and then it would go to a stable idle. Just a little blip in the start-up idle. It started intermittent, and then eventually went to every time.

I did a start log of the car back then and nothing looked obvious to me.

Then here a few weeks ago, suddenly it would not hot start when running errands (first time ever). Took a bunch of tries (5 or 6) to get it going. I went ahead and upgraded to Auto Tech's and put in new HPFP's at the same time. Now...it starts like it did before...straight to a smooth idle. I am thinking it is not a coincidence.

Now that is starts better I will do a start log of it soon, just to compare. See what that looks like. When I have a little more data I'll post it up. Probably going to be a few weeks.


Added more info in my post here.

[snohman]

Reviving an old thread that is unfortunately now relevant for me. Over the last few months, dealing with some hard starts and two no starts (earlier in the two months) on my 2015 S6 (63k miles). Has been driving me crazy as initially I thought it was the battery causing the gasping for air type start up.

For those that have remedied with new fuel pumps, has the issue not come back since? Realize the two fuel pumps are bit more costly than I had thought - OEMs are roughly $500 each. Appreciate any feedback folks have here.

[qcrazy]

Fixed it for me. Runs/starts like a champ now!

[Alabama]

Then here a few weeks ago, suddenly it would not hot start when running errands (first time ever). Took a bunch of tries (5 or 6) to get it going. I went ahead and upgraded to Auto Tech's and put in new HPFP's at the same time. Now...it starts like it did before...straight to a smooth idle. I am thinking it is not a coincidence.

Idle questions: 1) Is "age" of the fuel pump more related to time since manufacture or miles driven? 2) What effect (if any) does fuel quality have on the pump (for example, keeping water out of the tank minimizes rust on those components)? 3) Am I overthinking the issue - if the pumps are working, don't worry; if they're not, replace with an upgrade in quality?

[qcrazy]

It is a wear item, which will be directly dependent on pump strokes. A decent, but not perfect, proxy would be mileage. Ethanol is harsh, and could have an effect on life. But hard to say if it would cause a material difference in life. My original pump died BEFORE I started running high ethanol.

It seems to me about 100k miles (+/-) isn't an uncommon area for this issue to start to show up. But this is generic, as use type certainly affects timing. And like everything, they can fail at anytime.

[Botbasher]

It is a wear item, which will be directly dependent on pump strokes. A decent, but not perfect, proxy would be mileage. Ethanol is harsh, and could have an effect on life. But hard to say if it would cause a material difference in life. My original pump died BEFORE I started running high ethanol.

It seems to me about 100k miles (+/-) isn't an uncommon area for this issue to start to show up. But this is generic, as use type certainly affects timing. And like everything, they can fail at anytime.

What are you considering the "wear" item? The seal? The piston? The follower? I would believe the seal being the main wear item. The DLC coating on the pistons is simply too hard to wear out!!

I had several go-rounds with rebuilding my HPFP on my A5 (one word Autotech... x3!) and the same OEM seal "felt" different depending on the Mfg of the piston (OEM v AT v 034). OEM and AT were both loose enough to the point that they would allow the piston to slide, where the 034 was so tight I almost thought I would damage it during assembly. Thankfully it didn't!!

The seals are not "special". I'll look for my pics of it, but I swear it was an Elring or SK seal, like any crank or camshaft seal.

Cheers,

KS

[qcrazy]

I'm sorry, you were saying something about an indestructible coating?!

97k miles, factory HPFP's, fully stock fuel system...
20230116_111432.jpg

The center seals were equally worn.

[Botbasher]

I'm sorry, you were saying something about an indestructible coating?!

I'll give you that one... I guess I should have ordered my thought.

My stock one looked exactly like the left side. Scared me to death knowing the issues others were having. I was only replacing because of going to E40 and running out of fuel at the top so I wasn't thinking about it being damaged. Putting it on my granite block at work, I measured between 0.00000-0.00005 (step resolution of my micrometer at that decimal place) deviation over the length of the worn area despite looking extremely worn as yours does. The shaft over it's length actually had more deviation than the worn area did.

I'd actually be more worried about the one on the right. Looks like the seal was barely contacting it compared to the other.

Out of the 5 pistons I had in hand (1 OEM, 3 Autotech and 1 034), my OEM looked like your left side and had no issues at all. The AT units slid through the seal without any effort and looked worse than the right with less than 500 miles on each when I returned them. I haven't had the 034 out since install, but it was hard to push through, so I'd hazard it'll look more like your left example, but with 10k E40 24psi boosted miles on it, it is working as well as the day I installed it!

It's a chicken/egg call. I'll split the difference with ya! The DLC coating wears, but I still do not think the shaft is the primary failure point in that chain. I think the seal goes bad and allows fuel to wash the oil off the shaft. Things spiral down from there. If OEM tolerances are anything like ATs were, I can see why failures are so hit/miss.

Cheers,

KS

[Audibellybutton]

Reading the beginning of this thread was kinda sad and frustrating. Oh how much was not common info in 2018 lol. People buying evap hoses n shit trying to fix that. I just want to hop in my time machine and go back to comment "HPFP!!"

those are all the tell tale signs on any of these cars. Even older audis had the same issue.

[Botbasher]

I just want to hop in my time machine and go back to comment "HPFP!!"

But even then they probably still wouldn't believe you and still try the cheap, quick or easy options first!!

It's human nature!

Cheers,

KS

[qcrazy]

I'll give you that one... I guess I should have ordered my thought.

My stock one looked exactly like the left side. Scared me to death knowing the issues others were having....

My left one was leaking. Right was "fine". Agree with you on failure mechanism. It can go along time, but when it goes, it goes. Like it almost "wears" out.

[snohman]

Swapped both mine out for new HPFPs today - already on the few starts it just sounds and feels a lot better. Hopefully resolved the issue for me. Sad that I only put 64k miles on it but it is an older car so perhaps age was more the factor for me. Also had to replace the coolant tank that had cracked and was slowly leaking - please no more for a year haha.

Thanks to Audibellybutton for showing me some cheaper OEM pumps - saved me a couple hundred bucks!

[PaoloLuvara02]

Hey guys i’ve been having this issue for a little while and it seems to be getting worse. Sometimes if i leave the car off for 5 mins it’ll die immediately after firing up. Usually starts somewhat fine during cold starts. But if the car is off for more than an hour it’ll start then die right away or start really rough and die a few seconds later. I have to give it a good amount of gas in order to start properly. Once it’s running properly i have no issues. Drives and runs fine and everything. Only has an issue when starting. My question is even if it runs perfectly fine after it’s started, could the starting issue still be the hpfp’s?

[snohman]

Hey guys i’ve been having this issue for a little while and it seems to be getting worse. Sometimes if i leave the car off for 5 mins it’ll die immediately after firing up. Usually starts somewhat fine during cold starts. But if the car is off for more than an hour it’ll start then die right away or start really rough and die a few seconds later. I have to give it a good amount of gas in order to start properly. Once it’s running properly i have no issues. Drives and runs fine and everything. Only has an issue when starting. My question is even if it runs perfectly fine after it’s started, could the starting issue still be the hpfp’s?

This was pretty much my issue - only a few times would it not be able to start at all. I was once stuck trying to start it for five minutes in my parking garage at work thinking I'd need to call a tow before it finally fired up. After starting, there was no issues and even the next time I started the car, it would sometimes be perfectly normal. After having a few more incidents like this though, I decided to swap them out entirely. Haven't had any hard or semi-hard starts since - but its only been four days.

[Audibellybutton]

This was pretty much my issue - only a few times would it not be able to start at all. I was once stuck trying to start it for five minutes in my parking garage at work thinking I'd need to call a tow before it finally fired up. After starting, there was no issues and even the next time I started the car, it would sometimes be perfectly normal. After having a few more incidents like this though, I decided to swap them out entirely. Haven't had any hard or semi-hard starts since - but its only been four days.

Im glad I was able to help! your issue should be a thing of the past now, im willing to bet. But only time will tell. Good luck with everything!

[PaoloLuvara02]

Any updates? How are the new pumps treating you? Fixed the issue?

- - - Updated - - -

This was pretty much my issue - only a few times would it not be able to start at all. I was once stuck trying to start it for five minutes in my parking garage at work thinking I'd need to call a tow before it finally fired up. After starting, there was no issues and even the next time I started the car, it would sometimes be perfectly normal. After having a few more incidents like this though, I decided to swap them out entirely. Haven't had any hard or semi-hard starts since - but its only been four days.

Any updates? How are the new pumps treating you? Fixed the issue?