Seicento Ignition/ECU problem

[wilse]

Hi all,

Despite being an avid fan/user of this forum for years I’ve finally decided to register to ask for help. I’ve exhausted as much as possible the current forum links regarding a problem I’ve got with my 2000 Seicento Sporting but have finally accepted ‘defeat’ and need some assistance. The problem I’ve got is intriguing to say the least. It starts first time every time but after approximately 15 minutes it completely dies, no shudder, no misfire, nothing, just stops. After happening twice (the second time being right outside my house, had to push it onto the drive!) I called a ‘breakdown’ mechanic who said it’s either the crankshaft sensor, HT leads and plugs or the ECU. Having changed the crankshaft sensor 3+ months earlier without problems he ruled this out. I then changed the leads and plugs but again after 15 minutes or so the car just dies. I read on numerous threads that it could be the coils so happily replaced these last Saturday. I anxiously sat on the edge of the drive clock watching while it ‘purred’ away, having fired up first time after replacing the coils. Yet again, 15 minutes in and it died. This time however it allowed me to instantly restart the engine but died again after 9 minutes at which point it wouldn’t start again. The fan kicked in a few times so I don’t think it’s anything to do with overheating. As I say, it starts first time and runs normally without any spluttering or misfire and then just goes all stealth on me. I’m beginning to suspect it might be a bug in the ECU but would greatly appreciate your thoughts before forking out for a new one to be fitted/programmed.

Thanks in advance for your feedback.

Regards,

Wilse

 

[Most Easterly Pandas]

Why was the crankshaft sensor ruled out, just because it was changed 3 months previously? It could still be a faulty part!

Why was the original changed? I personally think its more likely to be this atm, even though its recently been changed.

 

[fingers99]

The only way to rule out the Crank Sensor is to check for spark and fuel past the injector(s) when the car has conked out. If either, it cannot be the crank sensor. If both, it certainly is. Get a "genuine" replacement from Fluffy the Impaler, FIAT, etc. You may have been sold a dodgy Chinese copy, even if it has Quinton Hazell stamped on it.

2000 could be SPI or MPI. If MPI, it makes sense to get the codes read. Any fool with a code reader can do it. A better code reader may be able to pick up the fault "live", as it occurs.

Although coil packs do fail, the chance of both coil packs failing at the same time is very remote.

I'd not rule out an earth fault or a dodgy engine temp sensor.

 

[rallycinq]

Right back to basics, why does it stop?

As suggested, check for spark and fuel, it must be either or both.

From there its easy to work out why its missing.

Cheers

D

 

[woj]

If it is an SPI, then the temp. sensor as Fingers suggested could be an issue. For MPI rather not, as you report that the fan works as expected, and in MPI this is ECU controlled.

Then, it does sound a bit like a dodgy RPM sensor, it is not an uncommon symptom for them to die when warm. As asked already, why was it replaced in the first place?

Finally, the fuel lines / filter could be clogged up, something to check. In MPI there is no fuel filter, you would have to take out the pump assembly and check the sieve there.

ECU wise, if it is an SPI, then 99.99% that it is not a problem. MPI - depends on the ECU, one series mounted in MPI is infamous, I never remember which exactly that is.

Oh, and yes, diagnostics / tester / code checker is always your first check to do.

 

[wilse]

Hi all,

Thanks for responding so quickly, much appreciated.

Had lots of starting problems so after researching potential issues i replaced the crank shaft sensor. Immediately fired up and had no issues with the car starting, both since fitting and now. I have basic knowledge about this sensor and understand how it controls, via the ecu, the firing timing etc but i don't get why it fires up and runs smoothly and then after an almost identical period of time it cuts out and stops. Is it perhaps linked to the engine temperature?

What's the 'safest' way to check for sparking after it's cut out? pull off an HT lead, fit a spare plug and see if it sparks? As you say, if no spark is apparent it seems to highlight a sensor issue. Wonder if i can get it replaced free as it's less than a year old?

Your continued advice would be appreciated.

wilse

 

[fingers99]

They tend to fail when hot (pretty common issue with electrical kit).

Best way to check for spark is as you'ver outlined. but do lie the plug on top of the rocker cover -- it needs a path to earth.

For SPI car, to check for fuel past the injector (only one), pull off the air cleaner cover and peer straight down the throttle body while someone cranks it. You should see fuel dribbling onto the butterfly.

On MPI cars, safest way is to look for fuel wet plugs (but not completely foolproof).

TDC sensor isn't so much controlled by the ECU as controls it: without a signal from the TDC sensor, the ECU thinks the engine isn't turning, so it doesn't fire the plugs or injectors.l

For MPI/SPI, SPI cars have a small, rectangular air cleaner housing, MPI cars a big, roundish one. There are pics in the guides/FAQs -- links at top of page.

 

[wilse]

Thanks for the feedback. I guess my first port of call is to check for sparks and fuel after it fails to see if it's a TDC sensor issue. If i get both then i guess i can rule that out, unless it has some heat affected issue that results after 15 minutes. I think it's the 15 minute timing that gets me; why so repetitive. I like the advice regarding the ECU realistically not being the problem. It's a rectangular air filter so an SPI engine. If i get sparks and fuel after it dies what do you advise is the next logical steps to check.

Again, feedback greaty appreciated.

wilse

 

[fingers99]

If i get sparks and fuel after it dies what do you advise is the next logical steps to check.

Perhaps not the most logical next step, but I'd next clean up all the visible erath leads in the engine compartment -- it won't take long, and it's free. Physically remove them, scratch up both ends until you see bright metal, coat with vaseline, re-attach. The main ones run from inner arch to top of gearbox -- I'm assuming 1108 -- and battery negative to inner arch.

Sometimes there's another, smaller, one, running from the coil pack and another to the ECU itself. On FIATs of this era earth are always black.

If that doesn't do the trick, swap out the engine temperature sensor. You'll find this on the inlet manifold, coded blue.

 

[wilse]

Hi all.

Latest update; just started the car, fired up first time, and let it run. Passed the 15 minute mark and all was well. At 19 minutes it seemed to splutter for a few seconds as if it was struggling but then continued as normal. This lasted for about a minute before dying. I'd already prepared a spare spark plug and lead so quickly whipped off one of the new leads and fitted it, laying the exposed plug on the rocker cover, as suggested. Got the wife to crank it over but got no spark. Removed the air filter housing to look into the carb and got m'lady to crank it over again. I didn't see any fuel 'dribbling' so can i assume the it's the crank shaft sensor that's faulty? The reason for replacing this last time was bad starting problems that eventually resulted in no starting at all, even after cleaning. Replaced it and had no starting issues at all, until now.

So all, am I off to buy another sensor or should i try a few other things first?

Advice apprecaited.

wilse:bang:

 

[fingers99]

I'd get another sensor. They're pernickity things at the best of times (which is why some folk fitting aftermarket ECUs have binned the original magnetic type for the more trustworthy hall sensor type -- unfortunately this -- probably -- Woj might know -- won't work with the standard ECU).

Big Mick (aka Fluffy the Impaler) at eurocarcare in Derby (Google will find) is probably your best/cheapest option.

 

[DannyCento]

Yes, don't waste time on it, get it changed under guarantee. And after fitting it check that the gap between it and the toothed pulley is as per the manual 0.5 to 1.5mm

 

[wilse]

Hi Fingers & Danny,

Thanks for your advice. Having searched hi and low i can't find the receipt for the last one i bought so going to have to buy another. Although the car spares shop (Central Auto Supplies) is just round the corner i'm hesitant on getting another from them in case they have/acquire another dud. Have looked at eurocarcare as you suggested but they haven't got anything listed on their website. Will call them tomorrow and see if they can get one down to me for the weekend. I'll keep you all posted.

Thanks.

wilse

 

[gyugyujol]

mate, so no excessive petrol smell and stuff?
i'm facing cutouts and smell. retightening the vacuum hoses somewhat made it better, but while constantly monitoring the ECU via Fiat3pin+usb whenever i am driving my Lambda Sensor error comes up occassionally and the water temperature sensor [not the one that controls the dashboard gauge, the other one the ECU uses] does not really change value while engine gets warm.

i dont really think the TDC sensor is the culprit as it had been changed 97 times, hadn't it?

over-/underfuelling or such?
i'm heading to the car parts store tomorrow to get the water temp sensor and replace it straight away. after that fingers crossed and testdrive with monitoring.

so u might look around other sensors as well. if urs is MPI it might be different. mine is SPI

 

[wilse]

Hi all,

I just wanted to update the post and be the bearer of good news. After biting the bullet and buying another crankshaft sensor I got the old girl running again this afternoon. The one i took off looked a little 'corroded' on the end so in hindsight perhaps i should have done the whole spark/fuel test and tried cleaning off the end of the sensor before blindly forking out for new plugs/leads and coils but hey ho, it should make her run better especially with the weather quickly deteriorating. Ran her for 30 minutes with occasional revving without any problems. While i had the car jacked up and wheel guards off i was also able to change over the windscreen washer pump tubes as the front motor has packed up and needed it working for it's soon to be booked mot. For those with this issue it takes seconds to change the tubes over, just learn from my impatience at not having a bottle at hand. Stuff pissed all over my leg before i managed to get the tube back on and find an empty bottle!!

I took her for a little spin and noticed the brakes were a bit soft but i think that's because she's been sitting idle for a couple of months. I'll give her a good boot before the mot to clean out the pipes and de-cake the brakes.

Thanks for all your advice and assistance with this. Hopefully this post will help others as much as it's helped me.

Keep up the good work boys. Will raise a beer or two in your honour later.

wilse