Lost power on highway, possible bad fuel pump

   #1  

nycayenne

Verified VCDS User
Verified
Joined
Nov 18, 2022
Messages
9
Reaction score
4
Location
NYC, USA
VCDS Serial number
C?ID=423256
Hi all, 2014 B8.5 A4 6MT with about 45k mi failed me on the highway yesterday. I'll include the full sequence of events along with the logs from my VCDS. I just realized as I sat down to do this post this is not a full autoscan, as I just clicked into the engine address today because there were no codes set on any other modules. I hope thats ok, if you're able to take my word for it.

I'm wondering if this is bad gas, a dying fuel pump, or something else. Could leaving the gas cap off really cause the car to lose fuel pressure/ kill the pump?

It was HOT yesterday in NJ, close to 100 degrees on the highway. I drove for about 1.5 hours, stopped and got gas, 91 octane.

Kept driving for maybe another 1 hour and 50 miles and was in 5th or 6th gear on the highway. I suddenly lost throttle response. As the car slowed I tried to downshift and was unable to get it into a different gear. The EPC light first came on and the check engine light came on seconds later.

I stopped on the shoulder and turned off the car. When I went to turn it back on I had a crank no start, epc and check engine lights. I left the car for 5 minutes, came back, it started, idled a bit rough, then smoothed out. EPC and CEL still on. I got it In 1st gear and it seemed to move fine. We got in the car and exited the highway to test a bit more.

Went around a parking lot and it drove great, got back on the highway. EPC and CEL Disappeared!! Drove about 10 minutes down the highway, lost power in 5th gear again. IIRC I was going uphill so the engine was well loaded at the time. EPC and CEL appear again. This time coasted all the way off the highway to the offramp. Stopped on the shoulder, crank no start, warning lights still on. I walked around the car to try to take a closer look, opened the fuel door and noticed the gas station attendant had left my gas cap completely off, like it was rattling inside the fuel door. I closed the gas cap properly at this time. Waited 5 minutes. Car started again, I got up to the exit's traffic light, it sputtered out again. Crank no start.

A Good Samaritan helped me roll the car into the lot, I left it. 10 mins crank no start. I left the car and took an uber to get a trailer... 1 hour later started up perfectly and drove into the trailer, CEL only now. 1 hour after that unloaded from the trailer, drove perfectly, CEL still set.

Today went out with my VCDS, car started up no problem, CEL still set. I got the attached logs, cleared the codes, and the car idled perfectly for 20mins, no new codes. On Friday I'm going to take it out just around town to load the engine again and see if I can get the issue to occur again.

Shall I replace the low pressure fuel pump? How do you identify bad gas? Any other thoughts?

Code:
Monday,08,July,2024,15:31:51:62643
VCDS -- Windows Based VAG/VAS Emulator Running on Windows 10 x64
VCDS Version: 24.5.0.0 (x64)  HEX-V2 CB: 0.4643.4
Data version: 20240429 DS355.0
www.Ross-Tech.com


VIN: WAUHFAFL3EN016192   License Plate: NJBREAKDOWN



--------------------------------------------------------------------------------
--------------------------------------------------------------------------------


                Address 01: Engine       Labels: 06H-907-115-CDN.clb
Control Module Part Number: 8K5 907 115 M    HW: 8K2 907 115 L
  Component and/or Version: 2.0l R4/4V TF H09 0005
           Software Coding: 4A190013242600062000
            Work Shop Code: WSC 62100 001 1048576
              ASAM Dataset: EV_ECM20TFS0118K5907115M 001006 (AU48)
                       ROD: EV_ECM20TFS0118K5907115M.rod
                      VCID: 3C213FDFE6E4ECDA4BB-8068
7 Faults Found:

4698 - Function Restriction due to Faults in Other Modules 
          U1113 00 [00100000] - -
          Intermittent - Not Confirmed - Tested Since Memory Clear

4699 - Function Restriction due to Faults in Other Modules 
          U1113 00 [00100000] - -
          Intermittent - Not Confirmed - Tested Since Memory Clear

4629 - ECM Power Relay Load Circuit 
          P068A 00 [01100000] - Opens Too Early
          Intermittent - Not Confirmed - Tested Since Memory Clear

10061 - Fuel Pump 
          P3043 00 [01101000] - Mechanical Malfunction
          Intermittent - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Priority: 2
                    Fault Frequency: 5
                    Mileage: 77366 km
                    Date: 2024.07.07
                    Time: 16:09:54

                    Engine RPM: 811.50 /min
                    Normed load value: 9.8 %
                    Vehicle speed: 43 km/h
                    Coolant temperature: 93 ∞C
                    Intake air temperature: 53 ∞C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 14.041 V
                    Unlearning counter according OBD: 40
                    Fuel pump: specified value: 29.254 %
                    Low fuel pressure: specified value: 400.0 kPa
                    Fuel temperature: 75.0 ∞C
                    Fuel pump adaptation: 0.0 kPa
                    High fuel pressure: specified value: 4.0000 MPa

10064 - Fuel Pump 
          P308D 00 [01100000] - RPM too Low
          Intermittent - Not Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Priority: 2
                    Fault Frequency: 1
                    Mileage: 77381 km
                    Date: 2024.07.07
                    Time: 16:42:10

                    Engine RPM: 799.00 /min
                    Normed load value: 15.7 %
                    Vehicle speed: 4 km/h
                    Coolant temperature: 93 ∞C
                    Intake air temperature: 58 ∞C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 12.769 V
                    Unlearning counter according OBD: 40
                    Fuel pump: specified value: 34.549 %
                    Low fuel pressure: specified value: 519.4 kPa
                    Fuel temperature: 25.5 ∞C
                    Fuel pump adaptation: 0.0 kPa
                    High fuel pressure: specified value: 4.0000 MPa

2838 - Fuel Rail/System Pressure 
          P0087 00 [01101000] - Too Low
          Intermittent - Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Priority: 2
                    Fault Frequency: 5
                    Mileage: 77367 km
                    Date: 2024.07.07
                    Time: 16:10:18

                    Engine RPM: 2226.00 /min
                    Normed load value: 12.2 %
                    Vehicle speed: 54 km/h
                    Coolant temperature: 91 ∞C
                    Intake air temperature: 51 ∞C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 14.041 V
                    Unlearning counter according OBD: 40
                    Engine status: COENG_RUNNING
                    Engine status-Test_Program_Co Eng st COMPU VERB UBYTE: 3

10530 - EVAP System 
          P0456 00 [01100000] - Very Small Leak Detected
          Intermittent - Not Confirmed - Tested Since Memory Clear
             Freeze Frame:
                    Fault Priority: 2
                    Fault Frequency: 1
                    Mileage: 75902 km
                    Date: 2024.05.24
                    Time: 10:00:04

                    Engine RPM: 1301.50 /min
                    Normed load value: 18.8 %
                    Vehicle speed: 0 km/h
                    Coolant temperature: 25 ∞C
                    Intake air temperature: 30 ∞C
                    Ambient air pressure: 1010 mbar
                    Voltage terminal 30: 13.264 V
                    Unlearning counter according OBD: 21
                    selected gear-Bits 0-7: 0
                    Acceleration: 0.000 m/s≤
                    Calculated reducing transmission intervention torque: 1000.0 Nm
                    Engine torque: 41.7 Nm
                    Required RPM at idle speed: 1300.0 /min


Readiness: 0000 0000
[\CODE]
 
   #2  

Uwe

Benevolent Dictator
Administrator
Joined
Jan 29, 2014
Messages
50,641
Reaction score
34,544
Location
USA
VCDS Serial number
HC100001
Could leaving the gas cap off really cause the car to lose fuel pressure/ kill the pump?
I doubt that.

the gas station attendant had left my gas cap completely off,
New Jersey? :rolleyes:

Shall I replace the low pressure fuel pump?
Based on the fault codes I'm seeing, that would be my guess as to the culprit, but it's just a guess.

How do you identify bad gas?
If it was bad gas, I wouldn't think the trouble would clear up after letting the car cool down.

-Uwe-
 
   #3  

EuroX

Professional User
Professional VCDS User
Joined
Jun 28, 2014
Messages
3,618
Reaction score
2,519
Location
Northern NJ USA
VCDS Serial number
C?ID=208579
pump or fuel pump control module if its got one.
 
   #4  

nycayenne

Verified VCDS User
Verified
Joined
Nov 18, 2022
Messages
9
Reaction score
4
Location
NYC, USA
VCDS Serial number
C?ID=423256
Thank you for the thoughful responses. My next step is road test and to inspect the pins on the connector to the fuel pump module, someone over on AudiWorld found burnt up connection pins after similar symptoms
 
   #5  

nycayenne

Verified VCDS User
Verified
Joined
Nov 18, 2022
Messages
9
Reaction score
4
Location
NYC, USA
VCDS Serial number
C?ID=423256
For anyone who references this thread in the future, please find related discussions on Audizine.

 
   #6  

EuroX

Professional User
Professional VCDS User
Joined
Jun 28, 2014
Messages
3,618
Reaction score
2,519
Location
Northern NJ USA
VCDS Serial number
C?ID=208579
Pointless to post discussions without knowing the cause or failure point. Perhaps for some it may be good reading. Personally I rather check and confirm. Repair and move on. This is nothing new in terms of common issues with these vehicles at least not for me.
 
   #7  

nycayenne

Verified VCDS User
Verified
Joined
Nov 18, 2022
Messages
9
Reaction score
4
Location
NYC, USA
VCDS Serial number
C?ID=423256
While it's true that I haven't finished diagnosing my own case, these other threads are the only ones similar to mine I found, out of many thousands of B8 / 2.0T discussions. Wouldn't you want to point another individual in the direction of useful info? Isn't this 'crowdsourcing' the exact premise of indentifix, and forums like the one we're on right now? By the way, and I mean this genuinely, thanks again for your input
 
  • Like
Reactions: Uwe
   #8  

EuroX

Professional User
Professional VCDS User
Joined
Jun 28, 2014
Messages
3,618
Reaction score
2,519
Location
Northern NJ USA
VCDS Serial number
C?ID=208579
While it's true that I haven't finished diagnosing my own case, these other threads are the only ones similar to mine I found, out of many thousands of B8 / 2.0T discussions. Wouldn't you want to point another individual in the direction of useful info? Isn't this 'crowdsourcing' the exact premise of indentifix, and forums like the one we're on right now? By the way, and I mean this genuinely, thanks again for your input
I agree it's good to have the information out there no doubt so that others have a reference of symptoms, the cause and the correction of issue. Often times there is some sort of misinformation in such threads. I like to stick to the facts at hand. Honestly Identifix is one of the worse possible ideas I've ever come across. It makes people into parts changers/parts cannon operators not technicians that can diagnose actual issues. Forums are hit and miss with information. I like to keep the details to the minimal but valid like ambient temp, engine temp. Condition under which the issue occurs like rpms,weather, terrain and so on. Minimum but valid in order to be able to duplicate the concern.
 
   #9  

Dr Sheldon

Verified VCDS User
Verified
Joined
Dec 5, 2014
Messages
1,034
Reaction score
484
Location
Windsor UK
VCDS Serial number
C?ID=334979
Nice easy one this

10061 - Fuel Pump
P3043 00 [01101000] - Mechanical Malfunction
Engine RPM: 811.50 /min

Low fuel pressure: specified value: 400.0 kPa

High fuel pressure: specified value: 4.0000 MPa

That looks like the specified values are 4 bar from the tank then The HP needs to be 40 bar at near idle.

10064 - Fuel Pump
P308D 00 [01100000] - RPM too Low
Intermittent - Not Confirmed - Tested Since Memory Clear

That MUST refer to the Tank pump as the Pump Control Module can see the pump RPM - It drives it !! Point being that this not indicating at HP Pump !!

2838 - Fuel Rail/System Pressure
P0087 00 [01101000] - Too Low

Rail Pressure is referring to the HP pump - It clearly reads RAIL - Point being that if LP is low then HP will be so this is likely a sympathy code.

I would say that the fault lays in the LP pump or unwanted restrictions in the lines - The FP module seems to be doing its job, however, to test it will require a scope. Ecu sends it PWM and it drives the pump the same way
 
   #10  

nycayenne

Verified VCDS User
Verified
Joined
Nov 18, 2022
Messages
9
Reaction score
4
Location
NYC, USA
VCDS Serial number
C?ID=423256
Thank you for the analysis - I'm comfortable testing DC stuff but I left my PWM knowledge back at my university's EE lab. I plan to inspect for physical damage to electronic connections on those components, and then I guess wait for the issue to arise again... or just replace the pump...

Any thoughts on the fuel temp on the P3043 freeze frame? 75C sounds toasty but I don't know where that sensor is located
 
   #11  

Dr Sheldon

Verified VCDS User
Verified
Joined
Dec 5, 2014
Messages
1,034
Reaction score
484
Location
Windsor UK
VCDS Serial number
C?ID=334979
Parts Darts is never my approach however I have an 8 chanel scope with Pressure transducers which will help me catch the culprit as soon as it misbehaves !!

In the absence of that I reckon you have enough there for it to be reasonable for you to condemn the Fuel pump ??

I'm comfortable testing DC stuff but I left my PWM knowledge
PWM is DC !!

Fuel temp seems plausible !


Bad gas wont affect Pump RPM unless it is contaminated with debris - Get the Fuel filter and cut it open !!
 
   #13  

Dr Sheldon

Verified VCDS User
Verified
Joined
Dec 5, 2014
Messages
1,034
Reaction score
484
Location
Windsor UK
VCDS Serial number
C?ID=334979
If it is under the seat it can be DIY !!
 
   #14  

nycayenne

Verified VCDS User
Verified
Joined
Nov 18, 2022
Messages
9
Reaction score
4
Location
NYC, USA
VCDS Serial number
C?ID=423256
I think I would DIY the under seat pump, I've done them before on other cars. This guy found what he believes to be a factory installation issue during his DIY. Not sure I buy it but definitely intrigued....

 
   #15  

EuroX

Professional User
Professional VCDS User
Joined
Jun 28, 2014
Messages
3,618
Reaction score
2,519
Location
Northern NJ USA
VCDS Serial number
C?ID=208579
Yes hammer and chisel to get the ring on is a great way to fuck shit up this is why posting such threads with DIY butchery is just ridiculous same reason why many cars burn to the ground shortly after a improper install or shotty worksmanship.

"For the plastic seal rings, heat them up a bit, toaster oven or light heat gun, then install. Did this on my Excursion and it worked well."

Yes great way to burn a car to the ground. Please do.
 
Back
Top