Stuff to think over
New member
Hi Folks,
I.ve been trying to fix a seicento 2000, 1108 SPI petrol for up to 8 weeks now, but don’t seem to be able to make the right diagnosis. I hope some expert (on fiat or just experience) can enlighten me a little as I seem to run out of options.
Below a Spartan translation of history and what I have checked. If the translation is not clear enough, please say so and I will look into it. Since I already tried a lot (and thought a lot about it J) it’s quite a long text.
Tnx in advance.
History.
I own the car for about 10 months now. Bought it in good faith without warranty for a fair price.
After a few weeks some trouble with the heater. I returned the car since I owned it for a week and didn’t have time to look into it myself. They released some air from the radiator, refilled and everything was fine. Winter went by and the heater went out of use.
At some point I had an overheating engine. All coolant was gone. I again did not have time. Several times I refilled and vented.. During the summer. Eventually I had time to fix things and arranged some workspace time.
One week before this time the car stopped accelerating in a normal manner. Injector fault lit up on the dash. Idle sounded fine, extremely slow revving gave no problems up to 100 kmh. As long as I did not want power and was very very patient the car drove me home. When I persisted in applying the gas to deep the engine would stall.
Since the coolant did not leak from anywhere I assumed the leak was inside the engine.
In the workspace I started with replacing the distribution belt and head gasket. I replace the first part of the exhaust pipe as it was crappy also. I made sure the timing was correct.. (As far as I can see)
I replaced fuel filter, oil filter and so on.
The problem remained. When looking directly into the injector and going with the sound I concluded there must be a lack of fuel during acceleration.
A fiat dealer read the ECU with a lot of trouble and gave me a list of possible causes, which are the well known sensors here and there. I have no actual fault codes as we speak.
After this a series of tests and exchanges were done in unloaded condition in workspace which I will list below.
The injection fault light turns on during acceleration only. When at constant rev weather this is idle or not, the light goes out after a few seconds. When playing with the gas pedal it glows up again as the problem arose again.
Pump pressure is constantly around 1 Bar as it should be. Before, during and after the problem arises, this pressure is constant. I exchanged the pump to be sure. No difference.
The return pipe gives plenty of fuel when running. Power is supplied to the pump at all times, so the pump relays is fine.
With a cold engine some (up to 3 or 4 times) heavy revving is possible.. after that time things only get worse. I figure this must be a cold start programming since the lambda probe is not heated yet and so on.
I figured the Cat might be obstructed to I tried with only the first exhaust bend and Lambda probe to be sure. (there is no Lambda probe after the cat) It didn’t make a noticeable difference.
When I add fuel in an artificial way, things are less bad.
I tried this by closing the return fuel line and thus pressure rose in the injector. This seemed to help a little.
I tried spraying xtra fuel in the throttle and this also had a positive effect.
In a later stage I artificially kept the fuel return relais open, with the same positive effect.
This made me more confident it was a fuel problem.
To be sure I cross checked with a other SPI unit, including throttle potentiometer and inlet temp probe. It made no difference at all… how are the odds of both of them having the same defect. BTW It came from a running car.
In a later stage I also cross checked the idle actuator, which also did not make any difference.
I manually clogged the air inlet leading the actuator to make sure it was closed. It made no difference.
I checked all mass points, cleaned and reconnected.
Actuator resistance is ok, ca 50 Ohms on both coils.
Injector resistance is ok.
MAP resistance is ok.
Lambda heater resistance is ok.. it heats when applying power to it.
Throttle potentiometer resistance is ok, although about ½ way the resistance goes down again.
Battery voltage is ok (14,xx V)
Cable between alternator and battery is ok.
Since the lack of fuel is not a direct defect of the injector, the ECU must not be extending the open time in the right way. Question is.. why won’t it.
I live-measured Lambda probe. After heating within a few minutes (increasing from 0,02 to 0,90 Volts) after starting it seems stuck on 0,9 Volt.
This would mean a rich mixture. This is always the case, on any engine speed, idle or stable on any RPM. When accelerating though it almost always directly drops to almost zero 0,0x Volt.
When looking and listening closely when running idle there seems to be too much fuel applied, which would explain the high Lambda readings.
To be sure I lend a brand new Lambda probe. The heater resistance was a little higher and I had to switch the wireing.
The new sensor heated a lot faster, but eventually came up with the same behavior in voltages and the engine problem remained the same. I tried for 1,5 hour to try and let the ECU ajust to the new sensor. It reported the same values, so it made no difference. After removing it, it was charcoal black. I replaced it with the original Lambda probe.
When connecting the Lambda probe but placing it outside the exhaust, it constantly reports a lean mixture (0,02 – 0,05 Volts (which is a fact)). It does not have any effect on the engine behavior though. The problem remains.
I connected the 3rd multimeter to the MAP sensor. It runs between 0,5 en 4,5 Volts. When sucked artificially it reacts quite fast. When closing the MAP hose (which I exchanged temporarily to be sure) during high vacuum (when running Idle) and so creating a false vacuum reading it did not have any effect on the engine behavior. When pulling out the hose during Idle running the engine sounds like it is going to stall, but keeps running in a hesitant way.
What puzzled me was the diagram in the workplace manual. It stated the MAP voltage should be around 4,5 Volts when on atmospheric pressure (ca. 1 bar) and lower, down to 0,5 volts when there is a vacuum applied to it. Later on I read something about this principle somewhere in the forums here also.
What I measured is about 0,5 volt when the engine is not running. When Idle (high vacuum, right ?) around 3,6 volts, just like when stable running on any RPM. When ballasting the engine, like in acceleration, this voltage drops to 0,xx Volt as does the Lambda voltage which drops to 0,0x Volts also. When slightly increasing RPM instead of abruptly applying gas, the MAP Voltage varies between 2 and 4 Volts and the engine seems fine. (e.g. sounds that way )
Why is my MAP behaving in a reverse order ? The cables and connections seem un-messed with.. otherwise I would think is was connected in a mirrored way somehow.
Can anyone confirm this behavior ?
Throttle potentiometer (2 of them) behave in the same way. Around 0,5 volts when Idle up to 4,5 Volts when fully opened. This seems ok from my point of view. Does anyone disagree ?
When fully heated the engine sometimes corrects the lack of fuel when kept on the verge of stalling for about 30 seconds or so.. it then picks up and RPM increases rapidly.. when the throttle is closed again and I try to rev again.. the problem reappears.
Fuel fume recirculation valve.. one of the problem points the dealer pointed out to me after reading the ECU.
It is checked by the ECU right after start for about one second it opens. There seems to be an alternating behavior from this relay. When running Idle it is closed (as it should be) when revving it opens. What I found strange is the alternating behavior of this relay. It sometimes switches on and of about 2-5 times a second (wild guess). When I connect an external powersupply to it, it permanently opens and when closed there seems an influence on engine behavior. This would mean it works fine. I am not sure about the quick alternating though. I tested the relay on resistance and it is ok. I connected an extra relay between the valve and the ECU and used external power for the valve to make sure the relay would not short circuit the ECU at some point. The switching was the same though. There is a one way valve on the Coalfilter which is for letting air in, according to the manual. Yet.. sometimes I can smell fuelfumes from the valve. Closing it with ducktape made no difference to engine behavior. All pipes from and to the filter are ok as far as I can detect.
The REV/TDC sensor was also a problem point according to the dealer.
Cables seem ok from what I can see. References state it should be a shielded cable due to the sensitive signal the sensor sends out, yet I can’t see any shieling up until it enters the big tree of cables. When removes the engine stalls immediately. There is room for movement from and to the crankshaft-gear within witch the engine keeps running. All tooth seem fine and there is no play on the crankshaft so the distance between the tooth and sensor is constant.
When measuring resistance though, it reads 1 KOhm when cold and 1,3 KOhm when warm where it should be between 550 and 650 or so according to the manual. Since the engine runs with the sensor in place and not when out of place I assume it is ok.. Yet it is strange and not knowing the RPM , I assume, would make it quite impossible for the ECU to calculate the right injector timing and so on. The manual also states the ECU can’t use a “standard” value for REV sensor data (which is logical) Can a sensor like this be half broken ?
Coolant temp sensor. I did not check it, but since the vent starts running when the engine gets warm, I assume it is ok. Am I right in assuming this ?
There also seems to be a minor leak in the radiator which I won’t fix until this problem is over…
We don’t service any person vehicles in our workshop, so we can’t do a 4-gass measurement and we don’t have a scope for checking injector frequency either.
For now I was wondering the following:
MAP sensor reading correct ?
REV sensor resistance ok ?
What may I have overlooked ?
Is the ECU running on safe (getting home) programming ? (Is there such a programming ?)
Is the ECU perhaps not interpreting the REV values right ?
Is the ECU indeed reset by ½ a day without power, or do I really have to do the stuff from the Haynes manual (running hot, fan start, fan stop, fan start, turn off engine, disconnect battery, wait, reconnect ?) Which one is right ?
I am thinking about:
A wild guess.. replacing the REV.. I can’t borrow.. have to buy… (EUR 40)
Assembling the ECU reader project somewhere on this forum, hoping to find new data an insights.
An ECU swap.. which will cost EUR 80,- (don’t know what I get) and EUR 200,- with 3 month warranty.
Opening up ECU to see if there is (liquid) damage. Resolder components on ECU PCB and perhaps..
Replacing the EEPROM with the one on this forum, or an original one, that is anyone can help me to obtain a chip containing the original software or a copy of it. (ECU is a standard MM: IAW 16FM.E6/6A37-C0)
I read a lot on this forum and I find a lot of well knowing enthusiasts here, so I really hope some bright mind sets me on track as I (almost) seem to be stuck on the verge of spending serious money on an old car not really knowing if it will solve the problem… Money is not the problem.. spending it without results is.
My hope is on you guys (and girls J)
Any insights are greatly appreciated.
I.ve been trying to fix a seicento 2000, 1108 SPI petrol for up to 8 weeks now, but don’t seem to be able to make the right diagnosis. I hope some expert (on fiat or just experience) can enlighten me a little as I seem to run out of options.
Below a Spartan translation of history and what I have checked. If the translation is not clear enough, please say so and I will look into it. Since I already tried a lot (and thought a lot about it J) it’s quite a long text.
Tnx in advance.
History.
I own the car for about 10 months now. Bought it in good faith without warranty for a fair price.
After a few weeks some trouble with the heater. I returned the car since I owned it for a week and didn’t have time to look into it myself. They released some air from the radiator, refilled and everything was fine. Winter went by and the heater went out of use.
At some point I had an overheating engine. All coolant was gone. I again did not have time. Several times I refilled and vented.. During the summer. Eventually I had time to fix things and arranged some workspace time.
One week before this time the car stopped accelerating in a normal manner. Injector fault lit up on the dash. Idle sounded fine, extremely slow revving gave no problems up to 100 kmh. As long as I did not want power and was very very patient the car drove me home. When I persisted in applying the gas to deep the engine would stall.
Since the coolant did not leak from anywhere I assumed the leak was inside the engine.
In the workspace I started with replacing the distribution belt and head gasket. I replace the first part of the exhaust pipe as it was crappy also. I made sure the timing was correct.. (As far as I can see)
I replaced fuel filter, oil filter and so on.
The problem remained. When looking directly into the injector and going with the sound I concluded there must be a lack of fuel during acceleration.
A fiat dealer read the ECU with a lot of trouble and gave me a list of possible causes, which are the well known sensors here and there. I have no actual fault codes as we speak.
After this a series of tests and exchanges were done in unloaded condition in workspace which I will list below.
The injection fault light turns on during acceleration only. When at constant rev weather this is idle or not, the light goes out after a few seconds. When playing with the gas pedal it glows up again as the problem arose again.
Pump pressure is constantly around 1 Bar as it should be. Before, during and after the problem arises, this pressure is constant. I exchanged the pump to be sure. No difference.
The return pipe gives plenty of fuel when running. Power is supplied to the pump at all times, so the pump relays is fine.
With a cold engine some (up to 3 or 4 times) heavy revving is possible.. after that time things only get worse. I figure this must be a cold start programming since the lambda probe is not heated yet and so on.
I figured the Cat might be obstructed to I tried with only the first exhaust bend and Lambda probe to be sure. (there is no Lambda probe after the cat) It didn’t make a noticeable difference.
When I add fuel in an artificial way, things are less bad.
I tried this by closing the return fuel line and thus pressure rose in the injector. This seemed to help a little.
I tried spraying xtra fuel in the throttle and this also had a positive effect.
In a later stage I artificially kept the fuel return relais open, with the same positive effect.
This made me more confident it was a fuel problem.
To be sure I cross checked with a other SPI unit, including throttle potentiometer and inlet temp probe. It made no difference at all… how are the odds of both of them having the same defect. BTW It came from a running car.
In a later stage I also cross checked the idle actuator, which also did not make any difference.
I manually clogged the air inlet leading the actuator to make sure it was closed. It made no difference.
I checked all mass points, cleaned and reconnected.
Actuator resistance is ok, ca 50 Ohms on both coils.
Injector resistance is ok.
MAP resistance is ok.
Lambda heater resistance is ok.. it heats when applying power to it.
Throttle potentiometer resistance is ok, although about ½ way the resistance goes down again.
Battery voltage is ok (14,xx V)
Cable between alternator and battery is ok.
Since the lack of fuel is not a direct defect of the injector, the ECU must not be extending the open time in the right way. Question is.. why won’t it.
I live-measured Lambda probe. After heating within a few minutes (increasing from 0,02 to 0,90 Volts) after starting it seems stuck on 0,9 Volt.
This would mean a rich mixture. This is always the case, on any engine speed, idle or stable on any RPM. When accelerating though it almost always directly drops to almost zero 0,0x Volt.
When looking and listening closely when running idle there seems to be too much fuel applied, which would explain the high Lambda readings.
To be sure I lend a brand new Lambda probe. The heater resistance was a little higher and I had to switch the wireing.
The new sensor heated a lot faster, but eventually came up with the same behavior in voltages and the engine problem remained the same. I tried for 1,5 hour to try and let the ECU ajust to the new sensor. It reported the same values, so it made no difference. After removing it, it was charcoal black. I replaced it with the original Lambda probe.
When connecting the Lambda probe but placing it outside the exhaust, it constantly reports a lean mixture (0,02 – 0,05 Volts (which is a fact)). It does not have any effect on the engine behavior though. The problem remains.
I connected the 3rd multimeter to the MAP sensor. It runs between 0,5 en 4,5 Volts. When sucked artificially it reacts quite fast. When closing the MAP hose (which I exchanged temporarily to be sure) during high vacuum (when running Idle) and so creating a false vacuum reading it did not have any effect on the engine behavior. When pulling out the hose during Idle running the engine sounds like it is going to stall, but keeps running in a hesitant way.
What puzzled me was the diagram in the workplace manual. It stated the MAP voltage should be around 4,5 Volts when on atmospheric pressure (ca. 1 bar) and lower, down to 0,5 volts when there is a vacuum applied to it. Later on I read something about this principle somewhere in the forums here also.
What I measured is about 0,5 volt when the engine is not running. When Idle (high vacuum, right ?) around 3,6 volts, just like when stable running on any RPM. When ballasting the engine, like in acceleration, this voltage drops to 0,xx Volt as does the Lambda voltage which drops to 0,0x Volts also. When slightly increasing RPM instead of abruptly applying gas, the MAP Voltage varies between 2 and 4 Volts and the engine seems fine. (e.g. sounds that way )
Why is my MAP behaving in a reverse order ? The cables and connections seem un-messed with.. otherwise I would think is was connected in a mirrored way somehow.
Can anyone confirm this behavior ?
Throttle potentiometer (2 of them) behave in the same way. Around 0,5 volts when Idle up to 4,5 Volts when fully opened. This seems ok from my point of view. Does anyone disagree ?
When fully heated the engine sometimes corrects the lack of fuel when kept on the verge of stalling for about 30 seconds or so.. it then picks up and RPM increases rapidly.. when the throttle is closed again and I try to rev again.. the problem reappears.
Fuel fume recirculation valve.. one of the problem points the dealer pointed out to me after reading the ECU.
It is checked by the ECU right after start for about one second it opens. There seems to be an alternating behavior from this relay. When running Idle it is closed (as it should be) when revving it opens. What I found strange is the alternating behavior of this relay. It sometimes switches on and of about 2-5 times a second (wild guess). When I connect an external powersupply to it, it permanently opens and when closed there seems an influence on engine behavior. This would mean it works fine. I am not sure about the quick alternating though. I tested the relay on resistance and it is ok. I connected an extra relay between the valve and the ECU and used external power for the valve to make sure the relay would not short circuit the ECU at some point. The switching was the same though. There is a one way valve on the Coalfilter which is for letting air in, according to the manual. Yet.. sometimes I can smell fuelfumes from the valve. Closing it with ducktape made no difference to engine behavior. All pipes from and to the filter are ok as far as I can detect.
The REV/TDC sensor was also a problem point according to the dealer.
Cables seem ok from what I can see. References state it should be a shielded cable due to the sensitive signal the sensor sends out, yet I can’t see any shieling up until it enters the big tree of cables. When removes the engine stalls immediately. There is room for movement from and to the crankshaft-gear within witch the engine keeps running. All tooth seem fine and there is no play on the crankshaft so the distance between the tooth and sensor is constant.
When measuring resistance though, it reads 1 KOhm when cold and 1,3 KOhm when warm where it should be between 550 and 650 or so according to the manual. Since the engine runs with the sensor in place and not when out of place I assume it is ok.. Yet it is strange and not knowing the RPM , I assume, would make it quite impossible for the ECU to calculate the right injector timing and so on. The manual also states the ECU can’t use a “standard” value for REV sensor data (which is logical) Can a sensor like this be half broken ?
Coolant temp sensor. I did not check it, but since the vent starts running when the engine gets warm, I assume it is ok. Am I right in assuming this ?
There also seems to be a minor leak in the radiator which I won’t fix until this problem is over…
We don’t service any person vehicles in our workshop, so we can’t do a 4-gass measurement and we don’t have a scope for checking injector frequency either.
For now I was wondering the following:
MAP sensor reading correct ?
REV sensor resistance ok ?
What may I have overlooked ?
Is the ECU running on safe (getting home) programming ? (Is there such a programming ?)
Is the ECU perhaps not interpreting the REV values right ?
Is the ECU indeed reset by ½ a day without power, or do I really have to do the stuff from the Haynes manual (running hot, fan start, fan stop, fan start, turn off engine, disconnect battery, wait, reconnect ?) Which one is right ?
I am thinking about:
A wild guess.. replacing the REV.. I can’t borrow.. have to buy… (EUR 40)
Assembling the ECU reader project somewhere on this forum, hoping to find new data an insights.
An ECU swap.. which will cost EUR 80,- (don’t know what I get) and EUR 200,- with 3 month warranty.
Opening up ECU to see if there is (liquid) damage. Resolder components on ECU PCB and perhaps..
Replacing the EEPROM with the one on this forum, or an original one, that is anyone can help me to obtain a chip containing the original software or a copy of it. (ECU is a standard MM: IAW 16FM.E6/6A37-C0)
I read a lot on this forum and I find a lot of well knowing enthusiasts here, so I really hope some bright mind sets me on track as I (almost) seem to be stuck on the verge of spending serious money on an old car not really knowing if it will solve the problem… Money is not the problem.. spending it without results is.
My hope is on you guys (and girls J)
Any insights are greatly appreciated.
