Krisco Kid

Hi all,

I have a 2001 A8L with about 170K on it. About three days ago the charging light came on intermittently (2-3 times) but didn't seem to affect the starting or driving. That is until yesterday.... I was 35 miles into a round trip when the battery warning came on. 10 miles later I was able to pull over but now before observing several warning lights come on one by one. After towing it home, I trickled charged the battery for 16 hours and got it back to full strength. Next I replaced the alternator with a new unit. It will turn over but not start. I have an Audi friend that thinks I should look at the fuel pump (they worked prior to the battery "drain", or that it could also be the "memory" which could be a big dollar repair. I don't have a VG but a there are no OBD II codes. Any advice as to what to check next?

silverd2

When you change (or disconnect) the battery, the 1st time you start it you must let the ignition switch stop at the "on" position for at least a few seconds before you turn it to start...this resets the ECM after the disconnect.
Try this 1st before you investigate further...you "might" (not sure) need to disconnect and reconnect the battery again. Then be sure to turn the switch on for about 5 seconds before continuing to the start position.

Krisco Kid

Silverd2,

I'll try it tomorrow. In the meantime, I did have it towed to a local garage and they seem to think that its a fuel pump issue to the tune of $1700 (no VG codes, just observing no fuel going to the injectors). I don't know how a fuel pump would go because of a drained battery but it could be coincidence I suppose. I hope it works as I expected to do some maintenance on the car, but I've already dumped $4k into the car (in 7 months) and can't afford it anymore. I my have to buy a laptop so that I can get the VC and the Bentley manual. It is a sweet ride.

K2

Krisco Kid

Thanks Silverd2 for your response. I have been able to do the checks you suggested and it still doesn't start up. It will turn over, but not start. I'm going after the fuel pump now and here's what I have found. The 4-pin connector on the fuel pumps shows 10.4 VDC across the brown and green/red wires. As I don't have a wire diagram for the pump, I am assuming that the these are the power leads. Additionally, when the car is turning over I can physically hear the pump "spinning" using a mechanics stethoscope. What I'd like to know is if there are any other quick tests before I buy a part that may or may not be bad (maybe a resistance check?). After that, it would be where one might buy a fuel pump? Are there other fuel pump configurations for an '01 A8L, 4.2L Quattro? And lastly, could a fuel filter prevent a car from starting as the A8L seems to have an oversized one .

JoePGT5S

If you can hear the pump spinning (in a consistent way) then it's probably ok. Before going to the effort of changing the pump I'd see about checking for fuel pressure first.

silverd2

You found the correct wires, but that voltage you read (10.4) may be an "off" reading. The pump only gets full voltage from the relay when the engine speed sensor (crank position sensor) is detecting that engine is turning (during cranking and running). The voltage at the leads needs to be checked during cranking and should read near full battery voltage at that time..12V +

Audi dealers and most independent mechanics will only replace the entire module ($800-900 part), but the only thing that goes wrong is the electric pump itself and possibly a kit of seals/gaskets. There are YouTube tutorials that explain the procedure. This will cost a fraction of the unnecessary Audi-version repair.

The correct pump (if needed), which is critical to get exact match, seems to be only available from overseas, but very easy to order and dependable, quick shipping suppliers.

Bargain US suppliers seem to ALWAYS have the wrong pumps, which lead to serious problems and invariably have to be replaced with the correct Siemens VDO pump.

One known good supplier:

http://www.worldcarparts.co.uk/Defau...language=en-GB

Krisco Kid

Unfortunately I ended up spending most of my Sunday working on my kids school projects. Two quick questions though, First, what is the fuel pump pressure spec'ed out at? Second, if 10.4 VDC is the actual reading at the pump, what is the next thing that I should look for? I did trickle charge the battery overnight so I can check this voltage again today after work. Thanks.

Krisco Kid

Sorry to be moving so slowly on this one guys, but I've been trying to baseline a few things first. First I should be able to check the fuel pressure today. I've read on the web here that the pressure should be around 60 psi.

I trickle charged the battery overnight and it read 12.6 VDC. I rechecked the voltage at the fuel pump yesterday and my meter read 10.8 VDC. Up from10.4 VDC prior to recharging the battery. Would a valid assumption be that the fuel pump was failing, thus drawing more current and causing the voltage low/hi warning light to come on and drain the battery?

And for what its worth, I took my old alternator (I actually bought the core) and had it checked by a local Autozone store. Their test showed that it was good. Interesting. I think I have to have it tested again somewhere else before I stop in to see the garage that put it in as they absolutely guaranteed me that the alt was bad.

Anyway, thanks for all the input so far guys. I'll let you know how I make out with the fuel pressure. I checked all the cars records last night and could not find any notice of a fuel pump replacement. Thanks again.

silverd2

Before you go any further, check this out:

I've never had a fuel pump problem, so am only going by other's comments and have never heard mention of actual voltage at the pump...your reading may be normal, according to something I found in Bentley (see drawings below). I haven't had a chance to check the voltage on my car, yet..but now I'm curious. Notice the comment at the bottom with blue arrow.

As you'll see, checking the pump is supposed to be done by volume over time, rather than pressure. I have never seen a case where the fuel filter was the culprit. So if your pump checks out OK (voltage and fuel volume at the engine), your no-start problem may be electrical..ECM not getting either spark signal or injector electrical signal where it needs to be(?).

But if you have no OBD codes showing, that is usually more indicative of a fuel pump problem, which generates no code of it's own. Even with pump running, it may not be getting enough fuel to the rails, due to it's failure or pressure regulator (less likely(?), the filter.

Hope this helps.

Bentley >>>

Krisco Kid

Thanks again silverd2 and Joe PTG5S for all the info and I suppose its time that I bring you all up to date. This has been such a great forum for me as I am new to Audi.

The original problem was that my A8L "died" while driving on the highway a month ago. It looked pretty much like the alternator was bad and drained the battery. As the battery was less than 8 months old, I charged it, and had the alternator replaced. As I don't have proper diagnostic tools to maintain the car, I've had a local garage do the work. The garage that replaced it , "swore" that the alt was bad, but never got the car started (as I had the car towed there after it died), and charged me $900 for the "service". I thought it was excessive but went ahead as I was looking for a dependable garage.

When the car wouldn't turn start, the garage "swore" that it was the fuel pump. They checked for codes (just an OBDII reader), and for fuel on the rail and they said there were no codes and no fuel. Oh and they wanted $1700 for a fuel pump assy (installed). Note: now it was my time to swear. So, I started reading the forums and realized I could replace the pump and actually start appreciating the "Audi".

I started with voltage at the fuel pump and it was approx. 10.6 VDC. Also, when the key was switched on it "sounded" like it was functioning. I next tried to perform the volumetric fuel test suggested by silverd2 but as I do not have the remote switches shown in the procedure I used the key switch to turn on the fuel pump. Also, I only removed the flex hose off the fuel pressure regulator (I left the high pressure hose on). No fuel output was observed. I next order a fuel pump from worldcarparts.com (approx. $200 with delivery from the UK to the east coast) and it seemed to be an exact replacement. I'm pretty sure I put it in per the you tube videos, but it did not solve the no-start problem.

So, I either installed it incorrectly, or it's not a fuel pump issue. It could also be that I haven't gotten the pump to prime itself (???? just thinking). There's about 1/3 of a tank of gas. Any suggestions?