Problem starting up. Please Help

[Bowlerwell]

Was just out to drop off a DVD.
I drove for less than 5 minutes, then stopped to head into Tesco.
Came out about 2 minutes later, and the car wouldn't start.
It turned over fine, but no start.
I left it for 5 minutes, and then it started as normal...

weird....

after taking 2 minutes to drive home, I tried again, and it wouldn't start.

Please help.
Any ideas what could be wrong, or how I could find out?

Thanks!

JohnB

[Knight Rider S4]

Immobilser sounds faulty

Play around with the ignition switch putting it on and off and see if it starts....not sure if there is a way to bypass some body else might know.......

Other faults could be fuel starvation but doubt it

Cheers

[Jas11n]

Classic sign of a failing hall sender.
Pouring cold water down behind the camshaft pulley when in a no-start situation sometimes sorts it for a while, but ultimately will need changing.
The hall sender tells the ecu the position of the camshaft/valves in relation to the crankshft position so it can fire the right cylinder on start up. If it can't see this signal it can't start. Once the engine is running, it can fail, but the engine will keep running taking it's info from crank sensor. IIRC ECU can also resrict boost if the hall sender fails to send a signal whilst running.

[Knight Rider S4]

Something new for me there......great advice

[Bowlerwell]

Thanks guys! Big help!

I'll pull the fault codes this evening when I get home from work.
Managed to drive to work this morning...
Would a faulty Hall Sensor be this intermittent?

Am I right in saying that there are 2 Hall Sensors? Are these easy to replace?

Thanks,

JohnB

p.s. Why does pouring water help?

[Jas11n]

Thanks guys! Big help!

I'll pull the fault codes this evening when I get home from work.
Managed to drive to work this morning...
Would a faulty Hall Sensor be this intermittent?

Am I right in saying that there are 2 Hall Sensors? Are these easy to replace?

Thanks,

JohnB

p.s. Why does pouring water help?

Yep, check the fault codes. If it is the hall sender, it should pull up code 00515 - hall sender G40. But it'll only come up if the hall sender is failing to give a signal at the time of the vag-gom test. (G28 will also come up if you do the test without engine running)
Certainly in my brothers experience it can be that intermittent, one minute would start, leave for two minutes then it wouldn't, leave for a further minute and she'd fire up. Sometimes whilst driving the car, he couldn't get it to boost beyond 5/6psi, when at other times it would boost fully. We've since learnt that the ECU will reel the boost back when it isn't seeing the signal from the hall sender (this was after replacing all sorts of other stuff)
Do a search on here for hall sender, I've read a good few posts on here where this has been the case in intermittent start problems.
Don't know for sure what pouring the water does, we followed this advice from these forums and it worked for a while, probably has something to do with cooling it.
There is only one hall sender on an ABY engine, it located behibd the camshaft pulley at the front of the engine. The wiring connector can be seen for it, sitting just above the top of the timing cover, at the end of and just below the fuel rail. Am I right in reading back through some of your recent posts that you've just had the head off the car? check that they plugged that connector in fully, or maybe it's full of oily crap?
My brother changed his himself on his car (95 aby coupe)
It involved the removal (for ease of access) the front slam panel, the aux rad, moving pas pump out of the way, removal of the timing belt cover, slackening of the timing belt tensioner, he tie wrapped the timing belt to the camshaft pulley, locked the engine then dropped the camshaft pulley off (tie wrapping the belt to the pulley saved having to re-time it) hall sender itself took all of 30 seconds to change, just a right PITA where it's located.
In all honesty, if it had been my car, it would have gone to my local specialists to be fixed, but my bro thought he could do it himself, that was 14 months ago now, so he must have done the job right.

I'm not saying 100% it's the problem in your case, but have a search on here for hall sender, you'll see it come up time and time again under intermittent start problems.

[Crawford_S2]

http://www.s2forum.com/forum/showthread.php?t=8658&highlight=sensor

[220bhp]

As they say hall sender, mine failed same simptoms, start some times not others.

[Bowlerwell]

Well done folks.

Ad thanks very much Jas for your extensive write-up. You always seem to be very helpful. Thanks!

VAG-COM gave 2 00515 faults. Of course, only 1 had a description.

Yep, Audi has had my car for 6 weeks. And strangely enough, the Hall Sender connection atthe front top of the engine is mounted the wrong way... I hope it wasn't them that damaged it...

Question:
Is the wire from the hall sender connection supposed to run under the black cover alongside the coil-pack cover (where the injector cables go...)?
Could it be possible that this cable to the ECU is faulty, and not the Hall Sender?

Thanks folks.

Looks like i'll be buying a new Hall Sender. I think i'll have to pay a mechanic to fit it... too much work for me just now.

[Jas11n]

VAG-COM gave 2 00515 faults. Of course, only 1 had a description.

The shareware version only gives a description for the first code, the rest are just the code. The fully registered version gives a brief desciption of each code it gives out.

Question:
Is the wire from the hall sender connection supposed to run under the black cover alongside the coil-pack cover (where the injector cables go...)?
Could it be possible that this cable to the ECU is faulty, and not the Hall Sender?

Yes, that wire disappears off into the black cover that also houses the cables from each injector.
No idea as to cabling faulty.