A3 8V intermittent start

[Evo2RS3]

Hey all,

2015 A3 8v 2.0t Quattro has about 80k miles. Randomly (maybe twice a month) will crank but not turn over. Takes about 3 tries before it starts up and runs fine after that.
Audi dealership says there’s no codes so they don’t know where to look or what it could be and send me on my way.
I’ve replaced spark plugs and camshaft sensor so far and problem still occurs.
I’d like to try crank position sensor next - does anyone have a diagram or can describe where it’s located on this vehicle?
Thanks for any help and ideas where to look next.

[MikTip]

Fuel, Fire, Air.

Audi dealerships are suppose to know basic mechanics...

They also have a factory Audi manual thats called Guided Fault Finding...tells'm step by step what to check to find issues...specific issues.

2015 Audi A3....9 years old...My guess would be the low pressure fuel pump.

There's an output test dealerships can do to check it...and the HPFP.

[Evo2RS3]

Thank you for that. That’s been more helpful than the dealership thus far.

They’ve had the car for a couple days now and plan to keep it over the weekend to see if they can replicate the starting issue.

So far, they said they haven’t encountered the issue but there was a one-time sporadic fault for oxygen sensor. Nothing else otherwise.

I’m wondering if I should just change the LPFP myself to see if it cures the problem.

[MikTip]

Thank you for that. That’s been more helpful than the dealership thus far.

They’ve had the car for a couple days now and plan to keep it over the weekend to see if they can replicate the starting issue.

So far, they said they haven’t encountered the issue but there was a one-time sporadic fault for oxygen sensor. Nothing else otherwise.

I’m wondering if I should just change the LPFP myself to see if it cures the problem.

That dealerships clueless...they have a manual that is used to find faults...and a manual for step by step how to test the LPFP...they use the Pressure Tester Kit - Regulator Valve -
VAS6550/4




When you open the car door do you hear the intank fuel pump run for 2 seconds? This pressurizes the system as it bleeds down over night...

[Evo2RS3]

That dealerships clueless...they have a manual that is used to find faults...and a manual for step by step how to test the LPFP...they use the Pressure Tester Kit - Regulator Valve -
VAS6550/4




When you open the car door do you hear the intank fuel pump run for 2 seconds? This pressurizes the system as it bleeds down over night...

To be fair, the car isn’t showing any faults or throwing codes. Just this intermittent start maybe once or twice a month.

I’ll listen for the pump if they return the car to me with no news.

[MikTip]

To be fair, the car isn’t showing any faults or throwing codes. Just this intermittent start maybe once or twice a month.

I’ll listen for the pump if they return the car to me with no news.

Theres no sensors on the LPFP to detect faults and throw any codes...

[texasboy21]

That dealerships clueless...they have a manual that is used to find faults...and a manual for step by step how to test the LPFP...they use the Pressure Tester Kit - Regulator Valve -
VAS6550/4




When you open the car door do you hear the intank fuel pump run for 2 seconds? This pressurizes the system as it bleeds down over night...

Are you capturing these images and process information via Erwin? https://audi-us.erwin-store.com/erwin/showHome.do

It may be nice to know what symptoms or issues must be present for Audi to perform a test like the example you shared here. Like you said, the techs 'know how' to dig into this stuff. It really must come down to a strict A>B>C process that must be followed, or an unwillingness to work haha.

[texasboy21]

Thank you for that. That’s been more helpful than the dealership thus far.

They’ve had the car for a couple days now and plan to keep it over the weekend to see if they can replicate the starting issue.

So far, they said they haven’t encountered the issue but there was a one-time sporadic fault for oxygen sensor. Nothing else otherwise.

I’m wondering if I should just change the LPFP myself to see if it cures the problem.

Sounds like you're willing to tackle some of the work yourself so I would highly advise getting a VagCom cable to help you. It's nearly dealership level access to all the modules which allows you to be access live data, and well as perform output tests - like the LP and HP fueling - before replacing parts. Its by far the most useful tool in any Audi owner's tool box.

https://store.ross-tech.com/shop/vchv2_ent/

[MikTip]

Are you capturing these images and process information via Erwin? https://audi-us.erwin-store.com/erwin/showHome.do

It may be nice to know what symptoms or issues must be present for Audi to perform a test like the example you shared here. Like you said, the techs 'know how' to dig into this stuff. It really must come down to a strict A>B>C process that must be followed, or an unwillingness to work haha.

Honesty...my experience is the dealer techs dont like to work on older cars. Anything 5 years or older...as they have already moved onto the newer cars and are in that mindset. Generally its one or two techs who can because they are the older techs who use to work on the older cars.

[Evo2RS3]

Honesty...my experience is the dealer techs dont like to work on older cars. Anything 5 years or older...as they have already moved onto the newer cars and are in that mindset. Generally its one or two techs who can because they are the older techs who use to work on the older cars.

Funny you say that as they straight up told me that they assigned my issue to a tech that’s been working for Audi for 20 years lol

[Evo2RS3]

Sounds like you're willing to tackle some of the work yourself so I would highly advise getting a VagCom cable to help you. It's nearly dealership level access to all the modules which allows you to be access live data, and well as perform output tests - like the LP and HP fueling - before replacing parts. Its by far the most useful tool in any Audi owner's tool box.

https://store.ross-tech.com/shop/vchv2_ent/

Always wanted to do this but am intimidated by the possibility of bricking something lol

[texasboy21]

Always wanted to do this but am intimidated by the possibility of bricking something lol

It may look old school-ish but it's a very intuitive UI once you figure out the basic format. It priceless.

[MikTip]

Funny you say that as they straight up told me that they assigned my issue to a tech that’s been working for Audi for 20 years lol

Bingo

[Evo2RS3]

Got the car back yesterday - they said they checked the fuel pump, all good. They couldn’t replicate the problem, not surprised since it doesn’t happen often, and said they couldn’t find any issues with the car - sent me on my way.
Filled up the gas tank after picking it up and today I have the start issue :-) Cranks and stops, takes 3 tries to start up.
I’m thinking it’s related to filling the tank - I’m using premium… no idea!

[MikTip]

The car has 2 fuel pumps...

One is inside the fuel tank. Called the Low pressure fuel pump. LPFP Its electric.

The other is on the engine...called the high pressure fuel pump....HPFP. Its mechanical.

The one I have been posting about is the in tank LPFP.

The LPFP supplies the HPFP with fuel.

Which fuel pump did they check?

To access the code, if any a OBD reader than can actually read the modules correctly is required.

However the LPFP has no sensors on it to throw any codes.

The HPFP has a sensor on top and the fuel rail has a pressure sensor.

The LPFP has a control module...that every time you open the door...primes the LPFP inside the tank to pressurixe the fuel system.

You should hear this...also you can hear how good or how bad the LPFP sounds while it primes...

Another concern is has the engine been carbon cleaned?

[MikTip]

The cars a 2015 2015 A3 8v 2.0t Quattro 80k miles...

For 9 years the electric low pressure fuel pump has been running every time the car is driven.

On my 2015 Audi S3 I changed fuel injectors...didn't fix issue. DIY pulled the low pressure pump from the tank. On the end of the small electric pump theres a filter...



This pump sits inside a basket...



Looking down at my LPFP I noticed the filter was black! Upon removal from the basket it was filled with debris...on the inside of the filter!



My guess its back flow from the fuel system and pump when the pump shuts down...

I changed my LPFP. My original fueling issue went away.

I noticed the sounds it made when priming the system....sounded like crap!

https://www.europaparts.com/fuel-pum...0919087ah.html

[Evo2RS3]

The cars a 2015 2015 A3 8v 2.0t Quattro 80k miles...

For 9 years the electric low pressure fuel pump has been running every time the car is driven.

On my 2015 Audi S3 I changed fuel injectors...didn't fix issue. DIY pulled the low pressure pump from the tank. On the end of the small electric pump theres a filter...



This pump sits inside a basket...



Looking down at my LPFP I noticed the filter was black! Upon removal from the basket it was filled with debris...on the inside of the filter!



My guess its back flow from the fuel system and pump when the pump shuts down...

I changed my LPFP. My original fueling issue went away.

I noticed the sounds it made when priming the system....sounded like crap!

https://www.europaparts.com/fuel-pum...0919087ah.html

Thank you. And this is what I thought all along - something with the fuel filter or debris getting agitated when pumping gas and suspended in the tank and the pump sucking it up and getting clogged. I’ll dig into this more.

[MikTip]

That filter on the LPFP....traps debris...on the inside...

[Evo2RS3]

That filter on the LPFP....traps debris...on the inside...

I do hear the pump when opening the door

[MikTip]

I do hear the pump when opening the door

And....how does it sound...????

[Evo2RS3]

And....how does it sound...????

Sounds the same as always - nothing out of the ordinary.

[ilikecookies]

Jumping in on this, 2015 Aud S3, same issue, long cranks but won't turn over, takes 2-3 tries.

Only happens after I start the car again after I driven it for a bit (around operating temperature).

Just hit 90k miles.

Replaced the fuel control pump module based on some youtube videos but that didn't solve anything.

Only code pulled from OBD11 was P025C00, Fuel pump module control circuit low.

Any ideas? Swap out the LPFP first or HPFP? or do I start somewhere else?

Car has not been carbon cleaned

[MikTip]

Jumping in on this, 2015 Aud S3, same issue, long cranks but won't turn over, takes 2-3 tries.

Only happens after I start the car again after I driven it for a bit (around operating temperature).

Just hit 90k miles.

Replaced the fuel control pump module based on some youtube videos but that didn't solve anything.

Only code pulled from OBD11 was P025C00, Fuel pump module control circuit low.

Any ideas? Swap out the LPFP first or HPFP? or do I start somewhere else?

Car has not been carbon cleaned

This entire post...previous posts/above is about the LPFP.

You changed the module that controls the LPFP...

The LPFP has been running since 2015...9 years...every time you drive the car. Its electric.

The HPFP is mechanical. It has a fuel pressure sensor on top of it as does the fuel rail...so you will get a code if its the HPFP.

The LPFP supplies fuel to the HPFP.

My guess the LPFP is bad...its 9 years old! Especially if you drive the tank on E all the time. It uses the gas in tank to keep cool.

[ilikecookies]

Replaced the LPFP and still experiencing the same issues, no codes - any ideas what part to throw at it next?

Cold start fine, if I drive for a bit and try to start up the car again that's when it has issues trying to turn over.

When I do a warm start, foot on the break, push start button and it struggles to turn over all I have to do is press on the gas pedal and it starts up fine right away, without pushing the gas pedal it won't turn over.

[MikTip]

Was the old pumps fiter all full of debris?

As the electrical fuel pump inside the take wears it draws more amps...which can effect the control module.

A "P025C00" code on an Audi indicates a "Fuel Pump Module Control Circuit Low," meaning the engine control module (ECM) is detecting a low voltage signal from the fuel pump control module, which could be caused by issues with the wiring, connectors, the fuel pump module itself, or even a faulty ECM.

Can you get a VCDS? Not sure the OBD11 reads all the modules good...

You can by used modules

https://www.ebay.com/itm/146274846967

Salvage yard in your state will have it as well...

[ilikecookies]

Was the old pumps fiter all full of debris?

As the electrical fuel pump inside the take wears it draws more amps...which can effect the control module.

A "P025C00" code on an Audi indicates a "Fuel Pump Module Control Circuit Low," meaning the engine control module (ECM) is detecting a low voltage signal from the fuel pump control module, which could be caused by issues with the wiring, connectors, the fuel pump module itself, or even a faulty ECM.

Can you get a VCDS? Not sure the OBD11 reads all the modules good...

You can by used modules

https://www.ebay.com/itm/146274846967

Salvage yard in your state will have it as well...

Module was the first thing I replaced before the LPFP.

Anyways, decided to install ANOTHER new LPFP...think it might've fixed the issue but now encountering another problem.

Filled up the gas tank to full but it's only reading 6/8th full - do I need to calibrate the fuel guage or is it likely that the float is getting caught on something?

Never filled it up all the way during the previous install so I'm not sure if this is normal.

[MikTip]

Module was the first thing I replaced before the LPFP.

Anyways, decided to install ANOTHER new LPFP...think it might've fixed the issue but now encountering another problem.

Filled up the gas tank to full but it's only reading 6/8th full - do I need to calibrate the fuel guage or is it likely that the float is getting caught on something?

Never filled it up all the way during the previous install so I'm not sure if this is normal.

You DIY the LPFP?

The fuel sending unit is a fragile POS. Lol! It can get caught on the lines inside the tank and or broken very easily...

Fantastic plastic.



I had same issue and found the white plastic that holds the float bar had broke...I temp repaired it with a small zip tie until a new lebvel sensor arrived....Fun!

[ilikecookies]

You DIY the LPFP?

The fuel sending unit is a fragile POS. Lol! It can get caught on the lines inside the tank and or broken very easily...

Fantastic plastic.



I had same issue and found the white plastic that holds the float bar had broke...I temp repaired it with a small zip tie until a new lebvel sensor arrived....Fun!

I guess it's a good thing I still have some extras laying around lol.

How low should I let the gas level get before opening it back up to take a look? I want to minimize the risk of fuel spilling - I'm assuming opening it at a full tank the gas will burst out when I open it up.

[MikTip]

I guess it's a good thing I still have some extras laying around lol.

How low should I let the gas level get before opening it back up to take a look? I want to minimize the risk of fuel spilling - I'm assuming opening it at a full tank the gas will burst out when I open it up.

It has to be below 1/2 or it will spill...best at 1/4.

[ilikecookies]

It has to be below 1/2 or it will spill...best at 1/4.

For those that come across this thread in the future, you want it at least at 1/4 lol.

Car finally threw a P0087 code, going to switch out the HPFP - any chance you know the difference between 06L127025T and 06L127027C?

Difference seems to be the port on that side, which is the version I currently have, but it is plugged, googling suggests that port is used for MPI, wondering if I can get away with using the 06L127027C without the port...but 2nd guessing because the difference between the 2 is about $300.

https://www.shopdap.com/06l127027c-vw-audi.html (w/o port)

https://www.shopdap.com/06l127025t-vw-audi.html (w/ port)

[MikTip]

Whats the part number of the one which came on the car from the factory?

Look at vehicle fitment:

https://www.genuineaudiparts.com/oem...pump-6l127027c

Theres 2 different vacuum pump housings too...for different pumps...

The C is for the A3...T for the S3

https://www.genuineaudiparts.com/oem...pump-6l127025t

The fuel pumps cam roller needs to be replaced with a new pump.

[ilikecookies]

Whats the part number of the one which came on the car from the factory?

Look at vehicle fitment:

https://www.genuineaudiparts.com/oem...pump-6l127027c

Theres 2 different vacuum pump housings too...for different pumps...

The C is for the A3...T for the S3

https://www.genuineaudiparts.com/oem...pump-6l127025t

The fuel pumps cam roller needs to be replaced with a new pump.

The C lists the 8V S3 as well!

I keep on reading about the cam roller but can't seem to find where it's located from videos

[MikTip]