Q7 won't start

[Michael O Neill]

Hi every one i Have a 2007 Q7 i'v had it from new there,s 65783 miles on it, my problem is sometimes it won't start like it has a bad battery or starter, the thing is i'v put a new starter & a new battery, new alternator, new starter relays also a new key reader has any of you good people have any idea what could be the problem thanks

[Bigdave1230]

When it won’t start does it turn over fast but not fire or slow like the battery is flat?

[Michael O Neill]

Like there’s a flat battery & even if I’ve been driving for a while, if I put jump leads on it fine & starts like there’s nothing wrong 

[Bigdave1230]

Mine was similar. Drive to a petrol station and the car would turn over like the battery was flat. Turn the ignition off and try again and maybe 2 or three time later it would fire up like normal. It was a corroded earth. I put an earth between the earth point where you jump start the car and the engine manifold and it’s been fine ever since. Audi said it’s quite common but people think it’s the starter so when Audi replace the starter they clean the earths at the same time it’s in the to do list issued by Audi uk. There’s a thread on the next page with the heading “poor start”. Have a look lower down. This site won’t let me post pictures because of a upload limit unfortunately so can’t show you mine

[Bigdave1230]

Sorry heading Is “Slow Start”

[Michael O Neill]

thanks but i'v already done the earths still same prob 

[Bigdave1230]

When you say you’ve done the earths do you mean you’ve cleaned them or tried a separate earth from the engine direct to the body. Have you checked the battery voltage with a multimeter. When the engine is running it should be  just over 14v. Does everything electrical work on the car (ie you don’t have a electric window that doesn’t work or something like that?

[Michael O Neill]

I have put 2new earth cables on from the engine to the body, I’m get 14.3 v at both engine & chassis & all is working fine 

[Bigdave1230]

🤔 Roughly how long after you turn the car off is it before it won’t start again

[Michael O Neill]

I could leave the car for week & it will start Frist time I turn it over then I could leave it for 5 minuets & it won’t turn over then if I take the keys out & put them back in it would start right away 

[niedzial1983]

Was the new battery codded in ?

[Michael O Neill]

Yes

[Michael O Neill]

Yes

[Bigdave1230]

If it won’t turn over at all then if you take the key out and put back in then it will then I don’t think it’s going to be battery related. It sounds more immobiliser related. There’s a start/access authorisation module on the steering column that the key reader talks to when the key is put in that would cause it to not turn over if it thought it was the wrong key etc. I’m guessing you’ve had a diagnostic check to see if it’s thrown any codes up. If you have a spare key I’d try using that to eliminate a key transponder issue. 

[Bigdave1230]

It sounds like you have changed quite a few bits already (starter, relays) so it’s narrowed down a bit but even so you could be changing parts until the cows come home without hitting the nail on the head and meanwhile the Q7 has turned into the 6 million dollar car! Audi dealers do a diagnostic only service for about £60 which I’d be tempted to do before changing anymore parts.

[Nycaudi]

hey michael, did you fix your issue? if yes how? am having same issue and have already replaced those parts you mentioned except the extra earth cable as i dont know which grounding points and i have v8 4.2 na version

[Magnet]

Hello NYC,

The original poster hasn’t returned to the forum for almost 2 years. I think you stand more change of getting a reply by sending him a PM.

Kind regards,

Gareth. 

[Nycaudi]

thanks