Technical Hot start issue with a twinair

[caoc9]

Hi

I know this is in the 500 section, but my engine is that same. Many more have bought the 500 I think, hense a better chance of somebody has experienced something similar...

I have my car (2015 Fiat Punto 0,9 101bhp Twinair. 143.000km) for about 9 months. The guy how sold it to me, was very admit about to use the right oil, he just had it serviced with new sparkplugs. It ran fine for ar few months, then startet to be reluctant to start when the engine is hot. As soon as it has cooled down (1-2 hours) it starts fine.

When it wont start (hot engine, but not necessarily very hot!), it cranks, and does not ignite (it sounds). This will/can continue many times over. Sometimes it ignites, and the engine stutter for a few seconds with very rough sound and few RPMs, no change if I press the accelerator, and then it dies. When it eventually gets going, it will do the stutter thing for a while 20-40 sec, and then runs completely normal, full throttle response and no issues what's so ever. When it is going it works normal. The car will smell like gasoline when I have struggled to start it, other wise no gasoline smell.

I have tried a lot to fix it, but still no luck.

I have change:
Oil change (Including an motor wash and filter)
Camshaft sensor (with ECU reset)
Throttel buddy (with ECU reset)
Crankshaft sensor (with ECU reset)
Tried a new set of coils

My mechanics has no idea what to do next, he is talking about maybe lack of cumbustion, the valve "lifters" (dot know the right word) or maybe the piston rings. But it does not sound right to me....

Any pointers would be most appreciated.

Kind Regards

Per

 

[A3jeroen]

Is your oilfilter 100% Ok? It needs oilpressure to operate the valves. There is a separate filter in the Uniair as well.

gr J

 

[caoc9]

Hi J

The oil filter was recently changed, but the issue was there before. I have not changed/cleaned the filter on the unfair module... Is that something I can check myself, where is it located?

Thanks for the pointer.

Regards

Per

 

[John202020]

Not an answer but a question for other members,
I wonder, assuming the valving is ok/uni air, if you trick the engine into thinking its cold would it start normally by say disconnecting the temp sensor-only one or more? It would be a simple test to try whilst it's playing up?
Petrol smell I'd say a result of lots of cranking?

 

[varesecrazy]

Hi again

Did 'your mechanic' find any error codes when plugging in to reset things

(The punto is strange -weird)

When in a FIAT specialist the official FIAT diagnostic equipment found
1340 logged fault instances..On my punto TA

One other question..
The main BLACK cable from Battery Negative to Motor -Gearbox

Did you have this replaced..?
some people find it can cause poor electrical supply

AND ITS CHEAP TO REPLACE

 

[caoc9]

Hi again

Did 'your mechanic' find any error codes when plugging in to reset things

(The punto is strange -weird)

When in a FIAT specialist the official FIAT diagnostic equipment found
1340 logged fault instances..On my punto TA

One other question..
The main BLACK cable from Battery Negative to Motor -Gearbox

Did you have this replaced..?
some people find it can cause poor electrical supply

AND ITS CHEAP TO REPLACE

No error codes. I originally went to a fiat dealership garage and they did not find any codes either. After 3 hours they cleaned the throttle body an claimed it fixed or I had to get a new one. I eventually did, but that did not fix the issue.
I have looked at the ground cable, it looks ok. Looks can be deceiving I know, but I have tried an additional ground cable between battery and engine when it won’t start, also no change…..

 

[varesecrazy]

Your problems with HOT starting:

Does it happen 100% of the time..or just 'some days' ?


I suspect you had a good car for 2 or 3 months.. because of COLD air temperatures

Warmer summer air is showing the issue


My panda 1.5 hour misfire is 'summer only'.. ok in the Winter

Its other problem is 100% repeatable..

Been there for 25,000 miles no change..

I am convinced it is a wrong reading from a temperature sensor

Both or my cars are 85 hp euro 5 and euro6

Yours appears to be what we called a' 105 ' in the uk (only in a 500 ..)

 

[caoc9]

Your problems with HOT starting:

Does it happen 100% of the time..or just 'some days' ?


I suspect you had a good car for 2 or 3 months.. because of COLD air temperatures

Warmer summer air is showing the issue


My panda 1.5 hour misfire is 'summer only'.. ok in the Winter

Its other problem is 100% repeatable..

Been there for 25,000 miles no change..

I am convinced it is a wrong reading from a temperature sensor

Both or my cars are 85 hp euro 5 and euro6

Yours appears to be what we called a' 105 ' in the uk (only in a 500 ..)

Not a 100% of the time. But it is more often now, than a few months ago.

Well I live en Denmark, so warm weather is normally not a problem. The problem started early February.

I’m for sure not ruling out a wrong temperature reading, but I do not experience any misfire once it is running, and the outside temperature is not a big factor I think.

Regards

Per

 

[caoc9]

The problem is still there:-( Could it be the boost pressure sensor (BOSCH 0 281 002 996)? It should contain a temperature sensor that could give a wrong reading to the ECU?

 

[varesecrazy]

The problem is still there:-( Could it be the boost pressure sensor (BOSCH 0 281 002 996)? It should contain a temperature sensor that could give a wrong reading to the ECU?

Hello again,

It is certainly worth investigating..

So it has been awkward to start HOT in both spring, summer and autumn...?

 

[caoc9]

Hello again,

It is certainly worth investigating..

So it has been awkward to start HOT in both spring, summer and autumn...?

Yes, the time of year is not really a factor. It’s normally the length of the tip…