JoePGT5S

The symptoms do seem to describe fuel starvation.

silverd2

Where did you source the pump?

Is it the correct Seimens/VDO pump? Statistically, ANY other brand is a mistake.

ONLY correct pump >>>

Audi A8 Fuel Pump - Original SIEMENS VDO | World Car Parts > Store

d2audia8guy

After some thinking...I'm going to do a leak down test and fuel pressure test.

d2audia8guy

OK guys...I solved the issue. It was a bad CRANK SHAFT POSITION SENSOR. The symptoms will resemble fuel not getting to the engine, bad o2 sensors,bad fuel pump or relay. What I did was replace the relay to see if it made a difference.... None.....OK fuel pump already replaced..checked fuel sending unit and relplaced o rings...?? New fuel filter too..and new air filter....cleaned injectors with liquimoly...spark plugs semi fouled because of normal wear most likely..I thought it was due to bad fuel pressure regulator....all Wrong....the main symptoms for the CRANK SHAFT POSITION SENSOR going bad is that you park the car over night...in the morning it'll crank with a no start....once you get the bitch to start she runs like normal....shut it off...starts back up no problems....its only over night that it won't start the next day...

d2audia8guy

I sourced it from vdo OEM parts. AutohausAZ.

JoePGT5S

Congratulations on finding the root cause. Interestingly I had the exact same issue on another car many many years ago and it turned out to be the crankshaft position sensor. Due to the intermittent nature of the issue it took a long time to troubleshoot. The actual sensor ended up being ok; however the connector it used to the engine wiring loom was the problem.

I'm glad your problem is solved.

d2audia8guy

OK turns out now there is no spark? Can't get it to start....wtf!!

silverd2

Quote:
Originally Posted by d2audia8guy View Post
OK guys... "bad o2 sensors," "the main symptoms for the CRANK SHAFT POSITION SENSOR going bad is that you park the car over night...in the morning it'll crank with a no start....once you get the bitch to start she runs like normal.."


Where are you getting this info? ...what are you reading or being told?

O2 sensors will NOT stop a car from starting or shut one off...they only trim the fuel mixture within a small map set by the MAF. The MAF can stop a car from starting or stall it out, but not the 02 sensors.

That is not necessarily a "main symptom" of the engine speed sensor ("crank position sensor") being bad...nothing to do with parking over night. The crank position sensor simple sends a signal to the ECM which in turn grounds the fuel pump relay to allow it to work...that's it, fuel or no fuel.

Have you run a VagCom on it (read codes) ?

If you are truly getting no spark (are you sure), look at your ECM...water in it? ...corroded connections?

d2audia8guy

Where i am getting the info is from what the car was doing....i am honestly doing a lot of guesswork here...I'm having it towed to a German specialist tomorrow morning, I'll keep you posted. Haven't checked the ecm myself, water got into cabin due to clogged drains awhile back...unclogged and pulled carpets to dry...ecm was fine....running out of ideas here....don't ever buy relays from O'Reilly auto parts...they are *******s if want to return it...I'll post the bag codes shortly...I haven't run them in last week or...the codes are from a month ago

d2audia8guy

Car is running now...I'm so pissed...thing didn't have gas in it apparently??? My fuel gauge is allegedly broken but I swear I had at least a half tank....twilight zone? I probably spent about $1000 over this while dilemma...grrrrrrr...pathetic