Technical Start stop.... then wont start.

[ruby67]

Hi,

We have a 2012/13 Fiat 500 1.2 petrol (Colour Therapy)

It's been to Fiat once, and it there now, has been for 2 weeks and they are stumped.

Symptoms:

Start-Stop system stops the car at traffic light etc. Car won't start.

If you push start the car it fires right up.

Turning the ignition key does nothing, no cranking no dimming of lights, no draw on battery, no clicking of starter.

If you change battery or 'jump' it nothing, see above.

If you bridge between the starter and the battery positive it starts right up.

Clutch switch is good.

Start-stop battery sensor is good.

Fitted new ground straps

Checked battery.


Simply put the ignition circuit is live but won't engage the starter. Seems like whatever the car does to 'stop' the car is still in force.

Leave it a while and it starts up, stop-starts fine and it might be days before it happens again. I've searched but can't find anything like this.

 

[typecastboy]

How bizarre, never heard that one before. Clearly a sensor or ECU fault, it’s a matter of elimination I’m afraid. MES may shed some light if you are near anyone that has it.

 

[jrkitching]

Welcome back!

This is an unusual one; I don't recall seeing anything quite like this before.

What happens when you run with S/S disabled (on your car you may need to disable it every time you start)?

 

[ruby67]

Thanks, I'm a classic VW Porsche guy so I'm used to problems, but used to fixing them in short order.

This does smell of a ECU / Software fault to me. When I've driven while this has been happening ( including a big 350mile trip to clear the pipes as it were) I disable the S/S. I've had no problems, but that's not really a 'fix'

Also we live in London and it's bad enough that half the South East of England drive in each day and pollute the locals air we don't want to be doing it ourselves as most on City driving is with the engine off anyway.

Hopefully Fiat spot something but half the battle is getting them to replicate the fault.

 

[John202020]

Bcm? immobiliser? Fuse/relay box/corrosion? Could be as simple as a snapped (internally ) starter signal wire as in rear hatch type fault?

 

[alexGS]

Bcm? immobiliser? Fuse/relay box/corrosion? Could be as simple as a snapped (internally ) starter signal wire as in rear hatch type fault?

I imagine the starter solenoid must be activated by a relay that might be faulty in this case; perhaps the key switch bypasses this relay, but the Start-Stop needs it?

You would expect that the engine ECU would include an actuator test for ‘engine start’. I’m always surprised when a dealer with official equipment isn’t able to pinpoint faults any better than we might. Surely they will find it...

-Alex

 

[randjepandje]

I think i had a similar issue on my 500 (2011, ta-85).

Normally i start my car, push S/S off and then start driving.
One time i forgot to push S/S off, i realized it when i was braking down for a red traffic light and pushed the S/S button right when S/S kicked in and turned the engine off. Actually it turned everything off..

That moment nothing was working anymore, no emergency lights, pulling out/in the ignition keys, nothing worked. (it was in central Amsterdam, so big traffic and panic in my head since people behind me were already having heavy hands on their claxons).
I didn't knew what i was doing or going to do, so i popped open the hood and saw nothing strange. When closed the hood i got back in the car, wanting to dial the police or insurance about what to do. At that same time i put back my keys in the car and it started!

it happened only once, but my S/S is working (tried id afterwards on numerous occasions in safe locations). I didn't try to reproduce the timing of pushing the S/S button at the moment S/S is kicking in....