Hi, Can anyone shed some light on this problem? I have a 1995 Audi A6 SE Estate (only 75000 miles) and it will not on some occasions start. It will turn over but not fire up then about 1/2 hour later will start first time and the problem will not occur for a further say 3 or 4 days. Every time I take it to the garage it behaves impecably and will only not start like at 3.00am this morning when I was called in to work. The garage says it can only diagnose the problem if the problem exists at the time. There is a factory immobiliser fitted with a dashboard light which functions but this does not seem to help as the light works OK. Any advice very welcome.

 

does it act up after fueling?

 

No not at all. It runs perfectly it's just on odd annoying occasions it won't fire up but if left for a time (say a few hours) it will start first time. For example 3.00am this morning numerous attempts to start it and get it to fire up and it wouldn't, When I got back home at 11.30am in a different car and started the Audi up it fired up first time. Since then OK it has started first time everytime but it will fail me again at sometime in the not too distant future (it might be 2 or 3 days time or a week. This has been going on for 3-4 weeks now. Very Peculiar. I do notice on occasions like today when it fired up and started at 11.30am it wasn't a clean start there was a very slight burbling from the ignition like it didn't take straight away, but it was only for a split second. The main Audi Dealer will only rely on his diagnostic machine and it has not gone wrong there, my local independent garage full of many wise and experienced mechanics also need the diagnotic test when the car is failing to start. So far whilst in the garage it has not once failed to start.

 

well looks like it is a weard problem ,if you need a DIAGNOSTIC program i can send it over to your email (VAG-COM if you find a interface for it )well like the diealer said it is hard to locate it but in case you have any fault code i may check it on WINElsa and it may help on the values ,i dont think that you have a problem with IMMOBILIZATOR becauuse if you have problem with it it want start at all.if it is diesel engine it may be the fuel injectors any of them is failing to supply with enough fuel and the engine may not start ,well if you need anything detailed from WINELSA just tell year model and engine first letters i will check it ,it could be fuel pipe i may say it is geeting air somewere and the fuel is getting back to the tank ,that will not show any FAULT CODE ,
HOPE helps .
BEKIM

 

So, does it do this when its hot? or when its cold? Or at any temp?

1. What I mean is, will it start great, then u drive somewhere shut it off, and try and restart 1/2 hr later and not start?
If so, maybe a vapour lock. Was common the the early 1980's Audis due to hot injectors.

2. Doesn't start when cold. You let it sit for a while, maybe overnight, then next morning is bad.
Could maybe to bleed back in the injection system. Sometimes bad check values in fuel injection system can do this. Maybe a cold start value, but urually they don't prevent it from starting, just make it hard to start when cold.

Is it moisture related? Meaning, does it due this on wet/damp days, but on dry days its okay?
COuld be bad wires, the can short and stop car from starting on damp days. When its running, pop the hood on a dark night, look for blue sparks along the wires. And listen for sharp clicks and snaps indicating that the wires are bad/leaking.


Sometimes things like bad coils, rotors, distrubutors can cause issues like this. The first thing is to narrow it down to either fuel or ignition. Usually this is done by listening to the engine when it doesn't start. If it fires oddly, or backfires, misfires, its likely ignition related.

If it sputters, then runs fine, its could be a fuel issue. How long since the fuel filter has been changed?

(LOL... Suddenly I realize how hard it is to convey years of automotive knowlege in a post. Hope this post might help. )

 

Thank you for all your replies they are very useful. The car is again in the garage as it started cold at 6.00am this morning then failed to start again at 11.15 am after being left for 5 hours. It doesn't matter if it's cold, warm, wet or dry the problem doesn't seem weather related. I have printed off all your comments and have forwarded them to the garage and I will keep you informed of any progress made. Once again many thanks and I shall make a Paypal donation to your website. £20 quid OK?

 

Hi,

Just something you can try to see if it might remedy the problem.

In another link on this site, someone asked a question about 'the engine popping' and backfires to which I had a similar problem but also mine sometimes was a bit temperemental starting.

My problem was to do with a solenoid that's linked to the air mass meter (near the air filter housing) and releases the build up of pressure in the fuel tank. When there's a build up of pressure in the fuel tank, this solenoid is supposed to cut in and release the pressure in the fuel tank. If you lift your bonnet up and leave the engine running, after a while you will hear the solenoid clicking away as it's releasing the pressure in the tank (that's if it's working correctly). We found that if we moved the solenoid slightly, it stopped clicking and if we put our ear to the petrol filler cap, you can hear it trying to suck air in through the filler cap and the engine noise changes dramatically. As soon as we enabled the solenoid again, it went back to normal. So I either have a dodgy solenoid or a break in the wiring, that sometimes cause the solenoid not to work and what I was getting was over-fuelling causing a backfire and sometimes hesitant starting next time I tried.

What I have done as an interim measure, until we know for sure whether it's the solenoid itself or the wiring, is to loosen the filler cap a turn or two so that air can get in through the filler cap. This has stopped the backfire AND the hesitant starting.

Obviously, this mightn't be your problem but it might be worth loosening your filler cap and seeing howthe car behaves for a few days. If it solves it, then it may be a solenoid problem. If not, then it's obviously something else but you haven't wasted money on a needless part.

Lui

 

Well it finally failed to start at the garage and the diagnostic machine is telling my mechanic that there is a fault with the Cam Belt sensor and also with the Crankshaft Sensor. I agreed to them replacing the Crankshaft Sensor (£70) and it still failed to start so I have now agreed for them to replace the Cam Belt Sensor an extra £200 on top!!!! As I have just had my Cam Belt changed by the same garage I am slightly perplexed and a little suspicious (I'm a born cynic) . They don't think it's a fuel problem although I have copied them the contributions from this website. I'll know more tomorrow (wednesday) when the Cam Belt Sensor arrives. Am I being given the runaround? Any ideas or thoughts most welcome.

 

Turned out to be faulty Camshaft Sensor and faulty Crankshaft Sensor. Parts £270, Labour not bad @ £50. Anyway thanks for all the posts and ideas, no doubt I'll be back.

 

Had a similar problem with my A6.
Changed the plugs and the engine temp ssensor and it start first time all the time now.
Hope this helps.