01A6Turbo

Hey all,
I always enjoy hearing comments/advice from my fellow forum members - sometimes over what the stealership has to say! lol Okay, so here it goes with as much information as I currently have/know:

On Friday, Oct 1, my 2001 Audi A6Q 2.7L died on me while on campus. I ended up having to get it towed home, where it now sits dead in my driveway. It started up that morning with absolutely no problems; the weather was around 60F. I let the car idle for 5+ mins. as I always do (it's a bi-turbo) and drove to school. Went to two classes (2 hours worth of sit time), went to car, started up, drove down to the other end of campus, parked the car, went inside to make up a test (15-20 mins. tops) came out, used the FOB, turned and started the car, it cranked, turned over and started VERY weak (when I say weak, I mean like putting and coughing for air to breathe for its life) and then died after < 15 secs. Restart attempt #2: it cranked, turned over, started, coughed for it's life again, and this time died after only 8-10 secs. Restart attempt #3: it cranked (and cranked good and strong) but would not turn over and start. Now, a car needs 3 things to start and run. 1) Fuel. 2) Spark 3) Air.

Facts:
#1 thing I did, whip out my OBDII & read for any codes. None.
3/4 Tank of Gas (93 Octane - purchased about 3 days beforehand) She has an APR 93-Octane High Performance Chip. She is and was in Chip mode.
Battery is between 12V-14V. About 12V while cranking. It is a rather new (< 1 year old) OEM Audi Battery.
While waiting for tow truck, checked all of the fuses (fuel pump, fuel pump relay, etc.) in the interior fuse panel as well as any significant ones that would affect starting the car in the power distribution box (engine bay) - all were in excellent shape. Notice I say excellent, not just good. Most of them are brand new. Each fuse slot was double checked to ensure the right ampage fuse was in the right slot.
The car was not even attempted to be jumped as I know it is not a battery issue. (> 12V cranking, all accessories work strong/bright, and she cranks like she owns the world - good & strong.) haha
Within the last 10k miles, I have replaced/the parts are rather new:
Fuel Filter
Due to misfires galore: I went up & beyond and replaced all 6 spark plugs (OEM & gapped correctly), 6 coils, (not the wires though), and 2 ICMs (Ignition Control Modules)
Brand new MAF sensor
New air filter (Every 10-15k miles)
I am due for an oil change though it's been about 6k miles (Mobil 1 Fully Syn.)

If I think of any other important helpful information I will edit this post.

So, I have it towed home and instantly think to check the fuel pump. I get my father to listen to the fuel pump, with the back seat pulled and the FP cover removed. I turn the car to ON (not start). He could neither feel nor hear the FP priming or running. It wasn't doing anything. So now I think "Okay, great. The FP finally died on me. That's a nice $300 out of my pocket " However, we decide the test the power going to the FP with a multimeter and with the car turned to ON, we could barely get a reading. I pulled out my Bentley manual and have been clueless; starring at the wiring diagrams, etc. b/c I'm no electrician lol My father also got the idea to test the fuel pump fuse socket with the multimeter and it seems like he had trouble getting anything (a reading) there as well.

Can you guys help me, please? You're brilliant automotive/mechanic brains & intelligence will be highly appreciated! I'm getting stuck here as to what to do next. In the morning I'm going to call my guy down at the dealership and run it past him, see what he thinks. He knows I know a lot about and work on my own cars and he likes that, so he never tries to B.S. me. Or so I think Stealers can never truly be trusted haha

If you guys need any more information / questions / etc. just ask! I'll recheck this thread often to look for updates/comments.

Thank you so much!

- Ben -

rs4-380

fuel pump is controlled by the ecu and will not necessarily be energized when the ignition is on and the engine is not cranking/running.

A6Gary

When you say you barely got a reading, did you measure 12V going to the fuel pump? If you did, my bet is the fuel pump as that's exactly what happened to my '98 Dodge Ram PU. It was running, then died; would crank, but not start. I don't have a Bentley Manual for a C5, so I can't diagnose the power circuit or lookup the fuel pump system for possible causes.

01A6Turbo

Thanks for the quick responses guys

Ok so rs4, I have always been under the impression that the FP primed itself when the key was turned to ON, right before Start, so it can feed fuel to the injectors during cranking/turn over/start...? I was wrong? So if I get my father to test the voltage while I crank it, it should get a reading, no? I was pretty sure we had tried testing it both just with it turned to ON and also with me cranking...worth a second shot though. I'm just wondering if I possibly have a short or wire damage, etc. I know for a fact I have a short to my rear dome lights, they only work intermittently unless you give it a good whack every now and then lol

A6Gary - I was 90% sure it is the FP also and thanks for the input! However, a new FP for my APB 2.7L is around $300...*aye!* I don't want to go dropping that much unless I'm sure I've tested/ruled out everything else - for instance, this power issue. Hopefully, rs4 is right though about it not being energized unless cranking/starting...but when we tested it, we tested both the FP itself, hooking it up to a 12V source and it did absolutely nothing, also causing me to believe further it is the FP that's dead. but when we went to read the voltage of the wiring harness that connects to the top of the FP, we got no reading as well.

Edd W

The fuel pump is only energised when the engine is turning over. I believe it is the spark which trigger the fuel pump relay to cut in. So, no spark now power to the pump.
If you connect up a 12v feed to the pump then thump the bottom of the tank with you fist, you may just stir it back into life for a limited time. If this happens, it proves it is the pump, but it should run when powered and you should be able to hear it.

01A6Turbo

Thank you for all of your input! I am 99.9% sure now that it is the FP itself. I just went out to straight wire the pump up to the battery and I figured "Ah what the heck, one more time I'll just try to start it." I reconnected the power source to the FP, turned the key and it started right up. Let it idle for about 3-4 mins and it didn't die out on me. Then I shut her down, let her sit for a minute or two, restarted her with success, she ran for about 30 secs and died. Restarted, ran for about 10-15 secs and died. Would you guys agree it is just the pump and not the wiring source, etc. before I go spend $300 on a new pump? lol

Just Me

well, on my A6 i've had no reason to find out. But on my C4, B3, B5, and 986 porsche the fuel pump was momentarily energized when the key was turned from off to "run", before the crank position is engaged. This in fact was one method of starting better when the pump or check valve began to fail.

Turn the key to run and listen carefully - you can hear it turn on, then off.

Are you sure C5s are different?

Grant

rs4-380

the pump will prime but when I say "not necessarily" I mean it will not remain energized more then a couple of seconds if the the ecu does not see that the engine is cranking or running.

Measuring for voltage at the pump with the ignition on is not an indicative test because it only primes for a few seconds. if you jump the pump directly to 12v and get nothing out of it I would say the pump is indeed your issue.

socalclimber

No. I think more testing is needed.

I'd hate to see you buy a new pump, only to find out, it's the wiring, a ground wire, fuel pump relay, or missing impulse signal that drives the fuel pump relay.

Better test: put a test light (LED is best) or volt meter on + and - of fuel pump wires (near pump) and turn ignition on. Do you get a momentary voltage reading (like others have suggested, although I don't know if A6's do this or not, early Audi's did this, like 4000's and 5000's)? Then, crank engine, do you get voltage indicating that relay and impulse electronics are working as they should?

Early Audi's and VW's got the impulse from the neg. side of the coil which got impulse from electronic ignition distributor (Hall generator). I suspect newer Audis get impulse from ECU.

Sometimes, fuel pump relays get sticky or burnt contacts and won't close or transmit power to pump. Is fuel pump relay fuse blown?

If you find fuel pump relay, tap it while cranking, it might "wake-up" and start working. If you want to test for impulse, do NOT use a regular test lamp, only use a high-impedance lest light like an LED light that won't load or harm sensitive engine electronics.

Good luck. Test twice and replace once!

Peter Badore

If you had a VAG-COM available you could activate the fuel pump via an output test and check fuel pressure or volume or both. And are you sure that there are no DTCs that could be shutting down the fuel pump relay?