No-Start condition

[PaulThBrit]

I have had a no start condition with my 2010 B8 A4 Quattro and the symptoms are always the same. It has been flat-bedded to the dealer (Jack Daniels Audi in Paramus NJ) three times and they have replaced the fuel pump, fuel pump relay, controller and the central computer. The car has 56,000 and all work was under warranty. I have just picked it up again and the diagnosis, after speaking with the main Audi tech support line they had suggested replacement of the fuel pump fuse wire/link.

The no-start symptoms are:
- Car will always start OK from cold. I am in Northern NJ and starting at zero F has not been a problem
- Typically I will drive somewhere, stop and then go to re-start and it will crank and not start.
- The first time this happened was after a two hour drive, then it happened again a month later after driving only 1.5 miles into town.
- The first time it happened it was obvious there was a serious problem and I called AAA for a tow. While waiting I continued to try to start it and eventually it started so I cancelled the tow. I then drove 10 miles, parked, the car started OK and was perfectly good for a month or so.
- Once or twice the car has started and idled very roughly then stalled. Similar to a very bad misfire or fuel starvation problem.
- Twice it has failed after coming out of a restaurant. 30-60 minute drive and 1.5 - 2 hours rest and then it will not start. Both times I waiting several hours to see if the problem would clear itself (as it did the first time) but it did not. The last time it happened I left it overnight and came back to it the following morning. After several tries it did start and I drove it to the flat-bed.
- Several times while trying to start it, the car will continue cranking when my finger is removed from the key.
- Twice it has started normally, and then while I was sat there with the engine idling, the ESP warning light came on, then the TPMS warning light, a warning buzzer and then it stalled and would not run.

I have no confidence that the latest fix (the fuel pump fuse wire) fixed the problem. Everything is OK now and I am continuously going outside and starting it to try and make it fail. I do not want another 110 mile tow.

Questions:
1) Has anyone else seen this or have any idea what the problem is?
2) If this does happen again, is there anything that I should try to do in order to get it started and get another data point? Maybe remove the battery wire and reconnect to 're-boot' the system?
3) Where is the fuel pump relay and the fuel pump fuse wire located on the B8 2.0T Quattro?

Thanks,

Paul

[S4'ed]

The "Low Pressure Fuel Pump Controller Module" is located under the rear seat bottom cushion. Other than that module, there is no "Fuel Pump Relay". Make sure they replaced this pump module with the latest revision, as these have a long history of working OK when cold, then intermittently failing when hot. The fuel pump itself is located below the pump module, inside the fuel tank.

Does the no-start condition occur when the fuel tank level is less than 1/2 ?

Disconnecting the battery does not "reboot" anything related to the fuel system/Engine ECU.

Are there any DTC codes stored in the Engine ECU ??

[PaulThBrit]

Thanks for your quick response. Good question on whether this happens only when the fuel is less than 1/2. I haven't seen a correlation with that but my guess is that most times the fuel was indeed <1/2 full.

In March the service report states that they replaced the DME control Module and AL Contr Unit.

The report states:
55904 Found Faults for signal error to fuel pump control unit. Removed fuel pump control unit tested power and ground at unit OK. Checked signal wiring from ECM to fuel pump control unit for open circuits none found. Found ECM faulty causing fault and ESP light. Replaced and recoded ECM. Cleared faults. Test drove car OK.
The service sheets state 'OpCode 20651950 Replace Fuel Pump Relay 35WA' and the part was a 4HO-9511-253-1 Relay.

In April they replaced the report states:
55904 Faults for fuel pump open circuit stored. Checked over system found no power at fuse for fuel pump. Checked fuel pump relay in ECM box. Found relay sticking open causing car not to start. Replaced fuel pump relay. Test drove Car OK'

Now in June:
56484 Perform GFF call helpline case #******. Check the wire to the fuel pump OK. Check the fuse SC3 re-secure the wire connection on the fuel pump. Try several times test OK. Replaced fuel pump fuse wire.

[S4'ed]

I asked about the fuel level when you have the problem because : Not sure on the B8, but some Quattro models have a split ("Saddle") fuel tank, and there is a transfer pump (electric?) to move fuel from the 'secondary" tank to the "main" tank (where the low pressure fuel pump is located). Maybe the transfer pump does not work all the time? Ask the mechanic if your car has a transfer pump, and if this was checked.

And, the things replaced during your March and April repairs apparently did not fix your problem...it is doubtfull those two things were really broken,,,,..so I think they are just "shot-gunning" a fix......

[PaulThBrit]

Understood. I think that the change-ot of fuel pump, control module and EEC were all well-educated guesses. Unfortunately it is me that is left stranded by the side of the road and with 100 mile tows when this happens!

One thing that I could never reconcile is that this has (luckily) never happened when I have been driving. Or first thing in the morning or after two weeks of not driving when I returned from an overseas trip. It happens once it has been started, driven somewhere and then re-started after 5 mins in one case and 1-2 hours in three cases.

I have no confidence in the car now. I was going to take it on a 800 mile road trip to New England next week, but will be in my wife's Fiat instead! That is a whole different driving experience!

Paul

[S4'ed]

Did they replace your Low Pressure Fuel Pump? That could be the culprit. Sometimes, as the pump motor spring-loaded brushes wear, they loose good contact with the commutator, and the fuel pump can intermittently fail to start when 12V power is applied. Next time the no start happens. bang on the bottom of the fuel tank (or on the top of the fuel pump, under the round access cover under the rear bench seat bottom cushion), which can be enough to jiggle the brushes so that the fuel pump will start running, when 12V is applied again when you retry to start it. There are no DTC codes that will be set by this worn-out brush condition of the pump (the ECU can't tell if the pump motor actually rotates when 12V is applied by the Fuel Pump Control Module). Once the pump starts running, it will continue to run, so this might explain why you never had the car die on you while driving.

Also, I think there are multiple (2 or 3) "Power Supply" relays, in the ECU cowl box, which supply power to various fuel injection/ECU circuits. Could be that one of the other relays, not yet replaced, is intermittent. Easy and not too expensive to just replace these too.

[PaulThBrit]

Great input S4'd. I was looking for input like this that might just work when and if I am stuck again. I re-read the service sheets wanting to see the part number of the fuel pump they replaced. It's not there. The sheet actually says 'Electric Fuel pump remove and reinstall' with no part number so it seems like they just inspected it. You may be onto something with a sticky or bad commutator on that pump.

I will whack the tank under the rear seat cover when and if it happens again, and the relays in the ECU cowl box which I assume is the one in the cowl underneath the windshield washer tank.

Thanks again,

Paul

[DPD314]

Just my 2 cents about JackDaniels - my car has always left there in worse shape than when I brought it in. I never ever had problem with Paul Miller Audi though.

[PaulThBrit]

Thanks for the tip DPD!