Ok guys, changed the switch, changed the FPR, no dice. ricoblanco our first suspicion...
 

was right. It's got to be fuel related.

The car will not start at first crank. It's as if the first crank primes it and the second crank starts it because there's fuel in the chamber.

It reminds me of my 72 TR6 with a manual choke.

I'm all ears. Help, please and thank you all for the input.

BTW the old switch was intact but I changed it anyway.

Here's my original post.
 

<ul><li><a href="https://forums.audiworld.com/a8/msgs/172536.phtml">https://forums.audiworld.com/a8/msgs/172536.phtml</a</li></ul>

Did you check the hall sensors?

Does it start and run?

What is a hall sensor?

It starts and runs, no codes, idles fine.

I read somewhere in here but it was refering on the 2.7T engine
 

that a bad Camshaft position sensor could give you a trouble like this. Some times the ECM can get a start point and sometimes it doesn't. Its not a big deal to check them if you have the VAG tool an LED test light a volt meter and the Bentley. If you need more information let me know. The sensors are identified as G-40 and G-163.

Wouldn't that cause it to start intermittently? My car always starts on the second crank.
 

No start first crank, start on second crank like a charm.

Well....
 

From what I understood is pure luck, it could go a week without any problem it could give trouble all day. I would check those two sensors and may be the speed sensor G28 as well.
----&gt; edit&gt;&gt;&gt; The post that I read was saying that the ECM is compensating as long as it can get one reference point. Now I don't know if this is true but if there is no or a wrong signal somethere then you have no fuel or spark, and once the ECM gets a reference point it starts.... its a good theory.... now you are the only one who can check :)
Good luck

Re: Well....
 

My original post was on 09/21, it's been doing the same thing since then. It is totally predictable. If I stop and start immediately it will start. If I stop and wait a couple of minutes no start on the first crank, start on second crank. After it starts no miss, accelerates fine and goes just like it should.

Fuel pressure regulator.

^^^Changed it a week ago.^^^

Re:Fuel injector leaking?
 

I'd bet that if the fuel pressure regulator is new, you have an injector leak issue. First crank resupplies fuel at the injectors, second allows for a start.

How do I diagnose?
 

If that's the case, would injectors need replacing or would it be seals???

does anyone think fuel pump? Isn't this what they do when they start to go?

Re: What is a hall sensor?
 

My wife's Mercedes was exhibiting similar symptoms, reluctant starting, no codes (at least no generic OBD II codes, all I can scan on that car). After checking around a bit on listservs I replaced the crancksaft position sensor, a five minute task, no further problem.

These sensors do poop out. They come from the giant Bosch factory of dubious sensors, I imagine.

You can diagnose lack of residual fuel pressure by Tee-ing a gauge between the fuel rail and the hose, or, not having a gauge, what I would do is get some paper towels, a fire extinguisher,and 14/17mm OE wrenches and see if a little fuel squirts out when you crack the fitting. NOT with the emgine running.

Re: What is a hall sensor?
 

When I replaced the FPR, fuel did squirt out when disconnecting hose to the FPR.

This was my first thought and my worst thought.

OK, so I've been thinking...
 

Maybe a good way to test for pressure on the fuel rail would be to turn the ignition to the "On" position (not start). You should hear the pump running for a second. Turn the ignition off and then "on" again. Let the pump run, then try starting the car. If it doesn't start right up, then maybe it is indeed the camshaft position sensor (CPS, hall). If the ECU is not getting a reading on the cam position, you're notting getting any spark until it does. <i>Maybe</i> by cranking the engine the first time helps the sensor index itself? The only problem with this theory is that there are 7 different codes for CPS failure and you said you have no codes.
I see you stated that fuel came out of the line when you replaced the FPR, so I'm assuming you're getting fuel from the pump. If you want to really confirm it though, you can disconnect the fuel line going to the FPR and turn the ignition on for a second. Fuel should spray everywhere and comfirm the fuel pump is indeed working (sounds messy and dangerous tho). Also, from what I've seen on the fuel pump issues, either the engine will cut out when the car is already running, take multiple attempts to start the car, or not start at all.

how many miles?

I video taped with my phone but the sound does not come through on you tube.
 

I taped 3 attempts so that you guys could see that it does the same thing every time. No start first crsnk, start second crank. I don't know if I mentioned that if I shut it off and immediately start, it starts like lightning.

If it is a cam sensor could the behaviour be so predictable?

^^^^117K^^^^

It will not hurt to change the CPS. It's only $80.80
 

<center><img src="http://pictureposter.audiworld.com/152346/0232101024.jpg"></center><p>The car has 117K I have nothing to lose by replacing it.
I'll see what happens after that.

Meh, I have $78.50 here--->
 

<a href="http://www.germanautoparts.com/Audi/A8/EngineElectrical/45/1">German Auto Parts</a>. Pay no attention to their note, you only need one sensor. I hope that does the trick. It sucks to have to throw parts at the car though.

Re: Meh, I have $78.50 here--->
 

So far this week, FPR, switch and I'm ordering a CPS. The car has 117K this is all stuff that would have probably failed in due time. I lie to myself and call it preventive maintenance.

Thanks for the heads up ricoblanco.

Re: Meh, I have $78.50 here--->
 

I have ordered parts from here lately. This guy actually answers the phone and will call you back, something unheard of lately.<ul><li><a href="http://www.foreignautomotiveparts.com/RenderScriptTemplate.epc?_cmd=epccat_VehicleWHD&am p;cookieID=2HB0HESZV2HB0HLRE5&amp;yearid=1999%40%4 01999&amp;makeid=AUDI%40%40AUDI&amp;engineid=13525 62%40%40A8+QUATTRO++%2F+V8%2D4172cc+4%2E2L+GA

hmmm., that's a liitle low for the pump to fail but sure sounds like it

Re: How do I diagnose?
 

I agree. I think an injector is leaking down. A couple of ways to diagnose. First with a fuel pressure guage hooked to the outlet of the fuel rail (where fuel pressure regulator sits) Turn engine over a couple of times; turn off and watch pressure guage. Or, pull injectors and rail up; turn engine over; turn off and watch tips of injectors for fuel drip. You might try putting in a bottle of Red Line SL1 in first to see if that clears something out. (Pour the whole bottle into the tank) Peter

The signs of the leaky fuel injector is a lot of smoke at start up and fuel in the oil.

^^^I have neither, thanks tozoM8.^^^