Car won't start checklist....

[tommyweaves]

Is it worth investigating the immobiliser? Very recently had a friend with 60 plate Smart car. Left lights on over a weekend, totally flat. Wouldn't do a damn thing even after a jump from another massive battery, half hour fast charge etc etc. Search on the net suggested the answer was locking/unlocking/rocking the car combo. Bizarrely it worked!

[cheshired5]

Originally Posted by tommyweaves

Is it worth investigating the immobiliser?

Yes, if all the other data had checked out but currently the low cranking rpm means that the ECM won't fire the injectors.

Until the basics are covered, investigating anything else isn't really useful.

I'm confident it'll fire up first time with a new battery.

[Semnoz]

Thanks for pointing this out. The S4 is indeed 'only' rated at 720CCA.

I'm swapping it for an S5 on the way home from work (and that is 800CCA !).

That's one big pricey battery. I'm aware that I probably could have got a dealer to replace it for less, but car is stuck on driveway and dealer is not on route to work....and I like Bosch batteries.

[tommyweaves]

Originally Posted by cheshired5

low cranking rpm means that the ECM won't fire the injectors.

That's interesting to know.

[Splodger]

How much can a battery on its last legs affect the way the car runs? Since mine was changed the car feels different/better whether that's just in my head or not I don't know?

[tommyweaves]

Originally Posted by Splodger

How much can a battery on its last legs affect the way the car runs? Since mine was changed the car feels different/better whether that's just in my head or not I don't know?

I'm no expert but I believe funny voltages etc can affect electronic modules. Mind you, my car definitely goes faster and drives better after I've washed it!

[cheshired5]

Originally Posted by Splodger

How much can a battery on its last legs affect the way the car runs? Since mine was changed the car feels different/better whether that's just in my head or not I don't know?

As mentioned, system voltage glitches can affect many aspects of engine management.
On a more fundamental level, a dying battery needs a larger current output from the alternator which in turn requires a stronger magnetic field that creates an extra load on the engine.

Now that you're sorted, I would check the electrical system to ensure that the previous battery failure was isolated and not caused by something else.

[Semnoz]

Originally Posted by cheshired5

Not sure I agree with your fuel filter suggestion.

If you follow the logic and guidance in the video, your fuel pressure is fine.
Your rpm however, is not ok neither is your cranking voltage.

The most obvious cause is a battery past its best but you could also run some simple multimeter tests on your starter motor to confirm its good operation.
There's a starter testing video on my YouTube channel too.

Thanks again - all appears to be sorted now after fitting the new battery.

It didn't start on its first attempt, but after waiting 10 minutes, I tried again and it powered up nicely, no hesitation. It cranks much quicker now

Comparing the Torque log outputs this time, on start-up, the ECU voltage dropped to its lowest reading of 9.87V at the same time the engine had reached 137rpm with 5769psi at the fuel rail.

The Torque logging interval isn't quite small enough as the next entry has the engine at 1011rpm, fuel pressure at 5863psi and ECU voltage at 11.02, and that's the point at which the Mass Air Flow Rate suddenly jumps, which I assumed means the engine has 'fired up'.

So I can't quite tell what at what engine speed injection/ignition began (I'd need to be logging hundreds of times per second to obtain that granularity). Yesterday, the engine speed didn't go above 160rpm and wouldn't fire, so it would have been interesting to see if today, the engine did fire up at about that same engine speed (160rpm or slightly above), which could imply the new battery was helping other aspects of the engine (as hinted in the previous comment from CheshireD5). But I'm going to assume it started because the new battery allowed the engine to quickly reach 200rpm and above.

It was nice to see on the log that after driving around for a few minutes and then turning the engine off, the battery rested at 12.93V, which is a nice healthy voltage.

Oh, and unsurprisingly, the windows move up and down quicker, the mirrors fold in quicker and finally the rear RHD central locking works ! I guess it all just needed a bit more juice. Obviously I can now say I should have changed the battery before, but I like to get the most out of old batteries and use my CTEK conditioner to keep it going.

Interestingly, the old battery was at least a Volvo marked item (so not crap) however, it's CCA rating is 700A, which isn't correct for this model of Volvo. I'd be interested to know how old this battery is:

[cheshired5]

Originally Posted by Semnoz

I'd be interested to know how old this battery is

The year and week number of the first charge is stamped on top of one of the terminals.

[Semnoz]

Originally Posted by cheshired5

The year and week number of the first charge is stamped on top of one of the terminals.

Haha - amazing. I knew the car's date of manufacture was the 1st of November 2007, and would you believe it: