trackfactory

On my way to the city to a concert on a Saturday night, my A8 started to sputter when I stopped for a red light just before entering the tunnel. I experianced a strange bucking and immediately thought it was the tranny. I recently had a "brand new" (from Audi) trans installed, and was thinking I got ripped off by the shop that installed it. Then, from a stop, when I tried to accelerate, I got a loss of power and the RMPs dropped to almost zero. When I took my foot off the gas, the RPMs went back to normal and the car idled normally. This happened a couple more times, until the care died (in the tunnel) and would not start anymore. The CEL started to flash, just before the car died.
A little history...a couple of months ago I posted a thread asking about a flashing CEL when doing 80 MPH on the highway, other times always on. The codes showed random missing on all cylinders. New set of Bosch Platinum plugs didn't do the trick. The recommendation was to clean the MAF. So I went to the local autoparts store and purchased a can or CRC MAF cleaner. Upon inspection of the MAF, I found the air filter very dirty and the air canister filled with about a half and inch of dirt and dust. After vacuuming out the canister, changing the filer and spraying down the sensor, vuala! the CEL went out! Sadly it came back on about 3 days later. Then about three weeks later I notice the light went out. I had gotten used to seeing it on, I didn't even notice when it went out. At first I thought, grreat, it must of taken the computer a while to adjust to the new MAF readings. But the next thing I know I'm dealing with a starting issue. Can anyone help??!! Do I need to replace the MAF??
I was reading up on some other posts and noticed a couple other references to another issue I'm having, A shuddering at low RPMs (about 1100 to 1500 RPMs) and the suggestion was it could be related to the MAF?? I asumed the shuddering was the "new" tranny that was just installed and was on my way back to the shop that installed it when the "no start" issue occured.

Sorry for the long post. Please help!!!

skiracer

Fuel Pump? Need to pull codes and post them here.

AudiChan

I had startup problem just a couple weeks ago... after researching a bunch it was my fuel pump. unfortunately it cost a fortune since it's a dealer part and everywhere i ask got it straight from dealer for ~$650 before tax and labor for the whole fuel pump assembly.

my symptom was cranking but not firing while battery good fuel good (more than half a tank). before my car totally didn't start one day, it took longer to start or took second or third try to start the car. anyway, replacing fuel pump and spark plugs, now i feel the car respond a hair better than before as far as the "lag" between press gas and car going strong.

some other people had experience with just the fuel level sensor was improperly installed or "unlevel" somehow, causing car won't start below 1/4 gas in the tank. some just had to replace the fuel pump relay...

i know how u feel as $$$$ keep dripping out of your pocket on this "investment;" hope it'll be fixed soon... mines took almost a month since i had some issues getting a used part from junk yard + Thanksgiving)... hope u have a second car to use for the meantime!

let us know what else u can recall or codes that u may be able to post.

Always Overcharged

Im with him -^^^^^^^^^ fuel pump-ouch

trackfactory

Thanks for the info.
The car cranks but doesn't start. Sometimes it sounds as if it wants to start but just sputters.

Is there an easy way to diagnose if it cold be the fuel pump relay besides replacing it?

When you say $650 for the pump assembly is that including labor?

How hard is it to replace that pump. I've done it on an infiniti Q45 before.

tozoM8

It could be the engine speed sensor too. Need codes.

tozoM8

If it sprays fuel everywhere then the pump is OK.

skiracer

You might want to put the end of the fuel line in a jar or something ;-)

AudiChan

Follow tozoM8's instruction and test the fuel distribution before you invest into a new fuel pump assembly. Mines totally not sending any gas out.

As for the fuel pump relay, you can use a multimeter to test it. The fuse box is located in the passenger side foot well.

$650 parts only. That is the entire fuel pump assembly. bcoz fuel pump is tucked inside this fuel pump relay, it'd take a lot more work (if possible) to take it out and replace it.

Most places will charge you 3 hrs of labor. I had to work with a mechanic friend of mines (posses all sorts of tools and goodies) and it really took just about an entire morning to do it.

Always Overcharged sent me some pictures of the step-by-step procedure (17 pages long with good diagram) that's all you need. Well, one of the step is EMPTY THE FUEL TANK. So, be sure you have something to suck it out of the tank if you desire to do it yourself.

BrianC72gt

Pull the codes before you do anything.

Regarding the pump, it is not as diabolically difficult to replace as some would have you believe. I wrote a tome on it some time ago and have replaced two successfully. On the second car, there was no drama whatsoever. The first time was just one chapter of a nightmare of epic proportions, but I have now attained a higher state of being and zen-like oneness with the fuel tank nether regions.

The fuel pump assembly will set you back like 500 smackers. Figure three hours of labor, four if they are ******* it. If you get a replacement thread-in fuel barb with the same thread as the banjo bolt on top of the assembly, you can confirm that the pump is properly installed wihtout having to "Drive the car around and see what happens" dopey-assed approach advocated by Bentley. You will have to access the fuel pump relay, pop its cover off and push the contacts closed to hotwire the pump, but that is also dead nuts simple to do.

Here is a nauseatingly long write-up of the second pump I installed:<ul><li><a href="https://forums.audiworld.com/a8/msgs/134668.phtml">https://forums.audiworld.com/a8/msgs/134668.phtml</a</li></ul>