Hi,
Just joined site today and was hoping someone may be able to help me with my Seicento 899 Spi 1999.

I took it for a drive and was sitting in traffic and the radiator fan came on. This was all fine as the engine didnt overheat and I got to my destination. Re-started the engine and came home absolutely fine. Went to use the car a week later, it started and chugged really badly with black smoke from the exhaust. Normally it revs up when starting from cold and then settles down.

I checked the plugs and they were all black as though the engine was getting too much fuel and not enough air. The air filter is clean and there was no obstruction in the piping. I took the top off the Spi unit and there was fuel entering the throttle body as normal. After trying to rev the engine hoping there may be a blockage let the engine idle, then I heard a popping noise coming from the injector/throttle body, the fuel stopped flowing and now it wont start at all! Only when you release the ignition key you get a spray of fuel from the injector. I removed the fuel inlet pipe from the side of the Spi and fuel comes through from the pump on turning the key. The plugs are wet but the engine just doesnt fire!

If anyone could help would be very greatful. Many thanks in advance!

I checked the plugs

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There's a couple of things that spring to mind (I had similar problems on a 94 Cinq).

The air idle valve - also known as the air idle bypass or a stepper motor - may be dirty and sticking (or even need replacing). It's on the throttle body and easy to take off. From the front of the car, look at the throttle body - the air bypass valve is on the left, lower down. It also has an electrical connector.

The other thing is the fuel pressure regulator, which is nothing more than a diaphragm with a spring - next to the injector and held on by 4 screws. Apart from checking the diaphragm for splits, there's not much else you can with it.

If the diaphragm is split that would allow fuel to literally gush through - and more likely than not, you'd smell the petrol.

Do the easy things first. Remove the air idle valve and clean it/the seat. Don't try and turn the valve body by hand. Just clean it... or replace it if you think it's faulty

Hi Glenn,
Thanks very much for your reply and help! I have already removed the clamp plate and injector and also the 4 bolt fuel pressure regulator, (1 bolt sheared off). The diaphragm and spring were all fine. I managed to get it done up tight enough to seal it. The injector had a clear area so you can see fuel inside it and it has fuel in there.


I will take the stepper motor off and clean it. Ive replaced the coolant temperature sensor as I thought this may be the cause of the problem when the rad fan came on as it was only £4, but this didn't work.


Will let you know what happens with the stepper motor. Many thanks again! Ashley.

centofan said:

Hi Glenn,
Thanks very much for your reply and help! I have already removed the clamp plate and injector and also the 4 bolt fuel pressure regulator, (1 bolt sheared off). The diaphragm and spring were all fine. I managed to get it done up tight enough to seal it. The injector had a clear area so you can see fuel inside it and it has fuel in there.


I will take the stepper motor off and clean it. Ive replaced the coolant temperature sensor as I thought this may be the cause of the problem when the rad fan came on as it was only £4, but this didn't work.


Will let you know what happens with the stepper motor. Many thanks again! Ashley.

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Could also be the crank shaft position sensor starting to break down.
Have a look to see if getting good quality regular sparks at plugs when cranking.

Ive replaced the coolant temperature sensor

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Does your particular engine have 2 sensors...? The earlier Cinq does.. One is for the temp gauge and the other sensor is part of the engine management system. However, I don't think it's a temperature sensor at fault.

I doubt very much if the fuel injector is at fault.. something in the management system is causing it to over-fuel (and overheat).

You're absolutely positive that no error codes are present?

Hi Jackwhoo.

Many thanks for your info. I took the crank sensor off a cleaned it up with brake fluid and the centre metal core now looks as good as new. I also tested the input voltage to the sensor and got a voltage reading of 2 volts.

Would this be the correct voltage for the sensor to work as I cannot find any specifications regarding the sensor?

Many thanks again! Ashley.

Hi again Glenn,

The sensor I replaced as I thought it may be this is the coolant temperature sensor. It fits on the thermostat housing and has a 2 pin blue plug connected to it.

I found the diagnostic plug on the ECU but its not the standard 16 pin type but a 3 pin type. I bought a convertor lead and plugged it into my V/W fault code reader as I havent got a Fiat reader but this didnt work. All it shows is "LINKING ERROR"

I will take the stepper motor off and clean it with some brake cleaner on Friday after work. Hopefully this will work!

Would you happen to know where I could obtain a Fiat 3 pin reader?

Many thanks again, Ashley.

You'll get one on ebay
https://www.ebay.co.uk/p/88g-Obd2-Diagnostic-Cable-Adapter-for-Fiat-ALFA-ROMEO-Lanica-Black/1843251392?iid=322275706331

The adapter needs to be connected to the car battery, too ..

However, having said that, my scanner was almost completely useless for the Cinq.

I believe - believe - that people on this forum use some software called mutiecuscan which can be downloaded for use onto a laptop. I think multiecuscan can be downloaded from somewhere on this forum website. No doubt someone else will point you in the right direction ..

Hi Glenn,
Just took the stepper motor of the side of the spi unit. Bolts were torx type and were very tight, but I managed to remove them ok. Ive sprayed the inside the unit and the stepper motor with carburettor cleaner and wiped them clean.
Theres a flat metal drive rod that comes out of the spi, which will not turn by hand. The stepper motor has a plastic disc inside it which looks like it should turn, but is solid.
I havent forced it as I only tryed moving the two items by hand. Is this disc in the stepper motor supposed to turn?
If so I will try and lever it as it has 9 grooves around the edge which I will be able to get a screwdriver into. Many thanks! Ashley.

Hi again Glenn.
The cable you pointed me to on e-bay I already have. This is the one I connected to my fault code reader and it didnt work.
The cables that connect to a battery wouldnt reach the car battery, so I ran it off a different battery. Just sent you another message regarding the stepper motor. All the best, Ashley.

The cable you pointed me to on e-bay I already have.

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It's a pain .. those early 3 pin connectors. I never had any success connecting, and nor did anybody else who tried using their own scanners.

You can always ask a Fiat dealership (who will charge you) - assuming they actually have the old type scanner.

Just as an afterthought - and assuming you have a spark - try disconnecting the electrical connector on your MAP. Then try and start/run the car. To check if you have a spark - you probably know - remove a spark plug but leave the lead connected, and let the plug rest on the engine block while the engine is cranked.

The symptom of a faulty MAP is 'kangaroo petrol', and the car may also cut out but restart immediately then cut out again. You may also get an erratic tickover, juddering, lack of power ...

For the home mechanic who has problems .. and there are no error codes (or no way of checking) it comes down to 'guessology'. You won't be the first or last to change sensors and units to try and cure the problem. We've all been there, done it, got the tee shirt and shouted at God ..

You've obviously done all the tings that anyone else would do. You're sure that fuel is coming into the throttle body, so that rules out a faulty fuel pump. If you've got a healthy spark that pretty much rules out the ignition system ..

... which brings us back to the fuel/air mix. The injector is obviously working but something is telling it to supply too much fuel (or not enough air..) - hence the black plugs.

Just as an aside - and I'm going back many years - probably before you were born - a popping noise from the exhaust indicated a too rich fuel mixture, whereas a popping noise from the carburettor indicated a too weak mixture. That was in the days of points and carbs. Now, of course it's all engine management systems..

Get somebody to crank the engine over while you spray wd40 around the INLET manifold. If you get a cloud of blue smoke (burnt wd40) from the exhaust, that points towards a perished/leaking inlet manifold gasket.

Though having said that, from the symptoms you describe, it does point towards a problem in the fuel/air mix. Sooty plugs= over rich mixture.

On a personal level, I would change the stepper motor as opposed to trying to do anything with it. If that didn't cure the problem I think I would then change the MAP. Or maybe I would change the MAP first ..

Both MAP and stepper motor are relatively inexpensive.

If you take your car to a workshop they'll charge a minimum of £50 an hour plus parts .. and it may not fix your problem..

Do it yourself, Ashley. If you replace something that was ok .. well, believe me, you ain't the first to do that ..

Hi Glenn,
Many thanks again for all your advise. You have been very helpful! Ive had the car for 11 years and its done 126000 miles. I bought it with 51000 on the clock in 2006, so I think ive had my moneys worth! Its just a shame to see it go for scrap for the sake of a sensor!!

I forgot to tell you that I did buy a MAP sensor before buying the Coolant Temperature Sensor, but this acted the same as what the old one did (when the engine was running!). Going back to the stepper motor that I removed earlier. Is the disc inside supposed to spin as it will not move at all. Just wondering if this may be the culprit!!Once again many thanks for all the info.

The stepper motor is supposed to turn - it varies the amount of air going through. I'm not too sure about the disk that you mention as mine didn't have one.

The stepper motor has something like 200 pre-ordained positions. Turning it by hand can play havoc with it, assuming it's working in the first place. I'm sure somebody who is a lot more knowledgeable than I am will write in and explain all about it.

But, as you say, it's a shame to scrap the car for the sake of a sensor. Your car has a value - literally - of about £60, scrap value. Personally, I would try another sensor to see what happens. It's always nice to see a 'valueless' car kept on the road just because somebody has bothered.