BidgeeRoad

Yesterday my C5 Allroad, with 210,000 km on the clock, would start but immediately die (go from 1000rpm to zero and stall).

After a tow, it seems to work again. Any thoughts?

The gory details:

1. I filled the petrol tank up (from near empty)
2. Drove 1.5 km, then parked
3. Car started fine
4. Drove another 1km, then parked.
5. 30 mins later, I attempted to start the car. It started easily, but immediately went from 1000rpm to zero and stalled a few seconds later. I tried 4 or 5 times and observed the same behaviour, pressing the accelerator pedal made little difference: maybe a couple of seconds longer before it stalled, but the revs didn't increase.
6. An hour later, the tow truck arrived. I tried to show the tow truck driver what was happening, but the car wouldn't start at all now. (I guess there was no fuel in the engine)
7. Car towed away.

That was yesterday. I'm pretty sure the immobilizer light was not lit on the dashboard. Until the above happened, I had no known issues with the car. Apart from an interference line showing on my reverse camera screen (ie when in reverse) which has been there only for the last couple of weeks (which suggests some electrical change).

Putting possible immobilizer issues to one side (and the reverse camera thingie), google suggests the issue might be fuel pump, vacuum hose to fuel pressure regulator, or maybe engine speed sensor aka crank position sensor.

Today I went back to the car, armed with my spare key just in case.

8. The car started first time with the spare key! (Then the towie found the other key; that one worked as well).

Only engine code with VCDS-Lite:
The towie told me they often tow cars with suspected fuel pump problems, then with the tow truck shaking them around a bit, they start afterwards.

Needless to say, the car has been towed to an Audi dealer to test the fuel delivery system.

I'm wondering whether the fact that it started after a tow is a clue which suggests to you guys what the problem might be?

I expect the dealer will recommend replacing the fuel pump as a precaution. Its done at least 80,000km at a minimum, but is probably the original part.

I'd really appreciate any other thoughts/suggestions as to what the audi dealer should check while they have the car. Its a 200km tow to the closest dealer, all the more reason to try to ensure the problem doesn't happen again.

thanks!

georgeb944

I have owned 5 of these C5 A6 cars and have replaced four fuel pumps.

In my experience, they give one warning (a hiccup or a temporary failure to start) before dying altogether.

My advice, before spending a large amount of cash for a tow to a faraway dealer, install a new fuel pump and save some cash for a local tow.

(I doubt that the cooling system has anything to do with it.)

rocketman4321

Your list of faults is good, and georgeb944 seems to have plenty of personal experience, so I'd put his advice first. Other intermittent starts I've had were fuel pump relay (Volvo/Bosch) which was sensitive to interior temperature where the relay lived, and crank sensor (Mercedes/Bosch) which would fail to restart warm, after driving. On the former one, the fuel pressure regulator was recommended as the next thing to check.

Good luck!

johnkk

re vacuum hose to fuel pressure regulator, if the hose has rotted, you will have too much fuel pressure at idle(lost vacuum to FPR). Car will run, but mileage will be bad with car running rich at idle. If regulator itself fails, you can tell immediately by being able to suck gas out of vacuum nipple with mity vac or mouth vac(be careful use long clear tubing to avoid mouthful).

I don't think either are causing your stalling problem. Hunch that fuel pump is the issue. I had a few hard starts as warning, but didn't heed until no start and tow.

SloopJohnB@mac.com

If the fuel pump is bad, either for pressure or volume delivery or current draw, that's another story. But there is no time/mileage replacement for the fuel pump.

You might consider replacing the fuel filter, however.

BidgeeRoad

Thanks a lot for the replies gents :-)

From your replies its sounds increasingly likely that she'll be getting a new fuel pump and fuel filter.

To be clear, its likely that the existing fuel pump has been in the car since new, so 15 years / 210,000 km. I can't be sure, since I'm the 3rd owner and don't have receipts for the first 100,000 km.

My roadside assist policy includes 1 "free" tow of up to 200km, so I've used that to get the car to an audi dealer.

SloopJohnB@mac.com

If you have fuel pressure and volume there's nothing wrong with the fuel pump. On Audis it's irritating to not have a 'schrader' valve to hook up a fuel pressure meter; you need an adapter for the banjo bolt to a fuel log but you still need fuel pressure!!

BidgeeRoad

The dealer determined the fuel pump needed to be replaced, by testing the wiring and flow.

So now I have a new fuel pump (local Goss brand, less than 1/4 the price of the OEM item here in Oz) and fuel filter.

Lost half a tank of fuel - the bottom half had metal filings and silt! Which is curious, since I always use "premium" fuel... but 210,000 km = ~420 tanks of fuel so I guess stuff does accumulate. And I guess that didn't help the pump to do its job, even with the filter (dunno whether it comes before or after the pump?).

Back on the road! Fingers cro$$ed that the problem is properly solved, and the Goss pump proves to be reliable...

Interestingly, the interference (scan line) in the reverse camera display on my aftermarket head unit has now gone away. So it seems that might have been related somehow to the failing fuel pump.

Thanks again for the insights

Harleyguy

The debris in the tank could very well have come from fuel pumps/ tanks at the petrol station. Especially if they have had any work done on their facility. Also, I make it a point not to fill up if there is a tanker off-loading. Go to another station or come back in a couple of hours. The off-loading will stir up crap in the bottom of the storage tank. The dispensing pumps have filters but they may not have been serviced regularly and can by-pass if they become clogged.