WRX starting problem following battery charge

[xRIEx]

I went to start it on Wednesday (after 4 days or so not being used) to discover the battery was flat. Got it charged (removed it from the car as the charger instructions advised), put it back in - it started after 6-8 seconds. Drove to work, and it started fine for the drive home later in the day.

The morning after, went to start it but it wouldn't turn at all - the central locking had been fine, and the dash had lit up until I turned the key all the way - not enough juice to turn the engine. So battery back out, back on charge. I guess the battery is on its way out but I thought I'd give it another go anyway.

I've put it back in this morning, tried starting it and there's plenty of power to turn the engine (I've had it for 30 or 40 seconds on the key, I would guess) - the problem is the engine won't fire, it's just the starter turning over and over.

Any ideas what could be wrong with it?

Thanks in advance.

[ScoobieWRX]

Could be immobiliser or crank sensor. Can you hear the fuel pump priming even though it won't start. If you can then it won't be your immobiliser and more likely your crank sensor or even possibly MAF sensor but with what you've described more likely crank sensor.

New battery would be my first port of call.

[xRIEx]

The immobiliser seemed to be working fine, deactivating as normal.

I'm pretty sure I could hear the fuel pump priming, but I'll have a proper listen.

I noticed in the manual it said after reconnecting the battery, switch the key to 'on' but not start for 10 seconds for the throttle sef-diagnosis to do its thing. Did that, obviously didn't make a difference.

[v8250]

sounds like not enough cranking power in the battery. how old is the battery? when replacing buy the same size battery, same post orientation, but find battery with max AH cranking output i.e BOSCH, VARTA, EXIDE etc. some come with 5yr guarantees these days...worth spending a little extra for the max cranking output -to- battery footprint. use this site for size/footprint/post position reference to manufacturer...it's very useful.

http://www.tayna.co.uk/Car-Batteries-C48.html

[xRIEx]

I don't know how old the battery is, only had the car 5 weeks. The current battery is a Varta D47.

[ScoobieWRX]

Either your battery is faulty or something is draining the battery. You would need to see how much draw there is on your battery when everything is switched off.

If you have a faulty crank sensor your car will definitely not start.

It might be an idea for you to get hold of either a VAG OBDII cable and a copy of Free SSM, or a cheap hand held OBDII diagnostic device device with LCD screen to check for and clear any DTC errors. They don't always throw up a check engine light so be mondful of that.

Also, when starting a scoob, do not touch the gas pedal either before or during the starting process.