Fiat Seicento - engine cutting out - help please!

Hello Stu

Crank position sensor (cps) is a good bet.

One key characteristic is that it fails when car has got to full temp. In the past I have identified a failing cps by spraying it with something cold, brake cleaner or similar will suffice. The cooling effect temporarily bringing back the cps into life.

Typically no fault codes will throw up from a failing cps

whilst I'm not normally an advocate of throwing components at a fault, for the relatively low cost of an aftermarket cps it would at least rule that out.

The Fiat diagnosis software you want is MultiEcuscan, there is a free version.

www.multiecuscan.net/

It does all the Fiat / Alfa group cars. If you go on the website you can see what connection type you need. I’m not sure with the Seicento, but with some of the similar era Alfa’s I’ve had a Vag-com Type cable will only get you into some of the functions, and an ELM type reader will get you into more. Fiat also transpose some pins in the OBD connector, so you need adapter cables (bought or DIY made) to access some ECUs, for example on my 166 to read fault codes on the automatic gearbox I had to get an adapter cable. All the info is on the MultiEcuscan website as to what functions you can access.

Regarding the actual fault, I think this apples to all the Fiat FIRE engines, but certainly on the 1.2 versions I’ve had, theres a hose that’s part of the crank breather assembly that connects under the air box. This can split with heat/time and cause some rough idling type issues, might be worth checking out?

Hi All,

I got the car round this morning and started investigations. Firstly, I can't find any air leaks, perished hoses or anything like that. The symptoms are that it drives fine on a 1 mile trip to the shops, always starts first time hot or cold, but any longer trips, when it's fully warmed up, cause the engine to cut out when you slow down or come off the throttle at a junction or to park. Again, always restarts. No EML light on while the engine is running, just that it comes on with the battery light when you first turn the key, and back on when it cuts out.

I removed the crank position sensor, noting it's a Magneti Marelli branded one (could be original?) and unplugged it. Checking it's resistance I get 1250 ohms across the two pins that give resistance, this drops by maybe 100 ohms if you pass a non metallic piece of metal near it. I tried warming it gently (at a safe distance) over the hob in my campervan and the resistance increased as it warmed up, to around 1550 ohms, but didn't lose resistance with the heat as I expected it might if failing? Cooling down it returned to around 1250 ohms.

I cleaned it up, refitted it and had a look at the camshaft position sensor, this gives around 600 ohms resistance, not sure if that's correct or not? I believe it's a hall effect sender rather than magnetic?

I've installed Mutliecuscan on my laptop and await the VAG-COM cable to see if that can throw any light on the subject. As it is, I still suspect the crank position sensor and am inclined to try replacing that next.

Any more input much appreciated!

Stu

Thanks, I’ve ordered that crank sensor - worth a gamble as it was under a fiver with discount code, pick it up tomorrow. I believe the car has been behaving itself a little better since I cleaned up the crank and cam sensors, so hopefully I’m on the right track.

My diagnostic cable arrived too so I’ll see if I can find anything out via that.

Thanks again :-)

Stu

Hi,

I wasn’t sure about HAAS either, and it certainly wouldn’t be my brand of choice but in terms of chucking £5 at a new part to eliminate it, worth a go as the alternatives were around 10x the price.

I scanned the ECU yesterday and found no DTCs, and my Mum reported that the car hasn’t cut out since I’d first cleaned up the cam and crank sensors a week ago. I swapped in the new crank sensor, drove it around for a while up to full temp and repeatedly tried to get it to cut out, and it wouldn’t. Scanned again, no DTCs so left it at that and put the old crank sensor in the boot for a spare just in case.

My Mum has since used it for a few local journeys on which it would cut out previously, and so far so good...! Fingers crossed :-)

Thanks
Stu