S8 D2 Lazy starter on hot start

[strummagnet]

Hi. I have been tootling about this weekend and had an issue Saturday where the car was slow in turning over when at normal operating temperature. Cold start was perfect but throughout the day just got gradually worse, when on the last very reluctant hot start I just took it home and dumped it on the drive.

Found this answer within a D3 thread and wondering if this could be the case?
http://forum.a8parts.co.uk/showpost....72&postcount=7

This morning car spun over with no issues when cold but once again sluggish on hot start (made sure I was back on the drive before attempting)

I have VCDS lite but there doesn't seem to be any error codes logged, no eml on either.

Any advice on next step?

[HPsauce]

Hmm, maybe not? It depends what you mean by "slow".
If by slow you mean the starter sounds less lively and the engine cranking more slowly then it's likely something else.
If by slow you mean it cranks as normal but takes longer to fire up then maybe.

I've had a few cars with CPS failure over the years and they tend to be pretty blatant and terminal unless the sensor is just a bit loose.
In my experience the car more likely just stops running, sometimes with a few misfires on the way down, rather than failing to start.

[strummagnet]

Originally Posted by HPsauce

If by slow you mean the starter sounds less lively and the engine cranking more slowly then it's likely something else.

Yes HP, very slow cranking to the point it feels like the battery has drained then the car catches. Runs perfectly normal afterwards.

[MikkiJayne]

Damn. I'm really sorry you're having problems with it

I'd probably change the starter first tbh. The junction box is new, and all the terminals are nice and clean so its unlikely to be a power problem.

We'll need to sort a time for you to bring it back once Andrew's is done.

[strummagnet]

Originally Posted by MikkiJayne

Damn. I'm really sorry you're having problems with it

I'd probably change the starter first tbh. The junction box is new, and all the terminals are nice and clean so its unlikely to be a power problem.

We'll need to sort a time for you to bring it back once Andrew's is done.

Its no problem MJ. I would expect some settling in so no drama. The car gets looks and comments which is positive, and any chance to cruise down to Devon is always a bonus

[strummagnet]

Originally Posted by MikkiJayne

I'd probably change the starter first tbh

Can you advise part number of replacement please?

[MikkiJayne]

077 911 023e

https://spareto.co.uk/products?utf8=...rds=077911023E

[MikkiJayne]

We sorted this out this morning - turns out it was the earth strap, although a slightly unusual presentation of the problem.

Obviously I cleaned all that stuff up when the engine was out, but measuring the voltage while running showed 14.2 at the junction box but only 13.3 at the battery. This left the battery only 40% charged (and unfortunately 40% health) hence the lazy starting. When I investigated further, I discovered a layer of grey aluminium oxide dust between the earth strap and the mounting block on the body. I think the reason it got worse to start when hot was that all this area gets hot as well and so everything expanded a bit, including the aluminium oxide dust, thus reducing the available voltage even more.

Cleaning up the terminals with some scotchbrite got rid of the dust, and with a replacement battery fitted it jumps to life as it should I gave everything a coat of waxoyl to hopefully prevent corrosion getting back in again.

[Conan_the_Librarian]

The Liberian is doing his happy dance!

[strummagnet]

Originally Posted by Conan_the_Librarian

The Liberian is doing his happy dance!

Yep. We put money on a certain Mr smug popping up