Technical Fiat stilo 1.2 Starting issue

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Technical Fiat stilo 1.2 Starting issue


New member
Feb 17, 2023
Hello everybody,

First of all, thank you for taking the time to read this post. It's my first post, I have no idea how everything here works so I'm open to suggestions from all of you.

I have a 2002 Fiat style 3 door with a 1200cc petrol engine that has been converted to LPG. This conversion was done about 2 years ago.

About 1 year ago the car started to misfire in the cold weather. It was difficult to start and the idle was unstable while the car was not warmed up. If I tried to drive the car before it was warm, it wouldn't have the strength to go. The RPM would just go down and I needed to put the throttle way down and almost rev the engine form it to be able to move.

At first this only happened on cold days but after a while it started to happen all the time. It was not starting for the first 3 to 4 key turns and them when finally started the issue as the mentioned above.

My father is a mechanic and has been trying to help me with this problem. At first we thought it might be the conversion to LPG. We disabled the whole system and the car was fine for a while. We turned the system back on but it was still fine. A few more weeks passed and the problem returned. In the meantime we have already changed the spark plugs 2 times, we have changed the crankshaft sensor but nothing worked. Twice the fuel pump failed. We thought that might be it. It has already had two new ones and the car is fine for a while but then the problem returns.

However, the last attempt we made was to replace the car's ECU. This was 4 months ago. The car was fine, even on very cold days there was no problem. We thought it was finally resolved. However yesterday the car started again with the same symptoms.

We don't know what else to try.

Have any of you had this problem or have any suggestions of what might be happening?

Thank you all! Have a good day.
Not sure if you're aware but if nothing else the LPG system needs its own regular maintenance including changing parts and recalibrating, usually done by the same outfit who fitted it for you in the first place.

If you disabled the LPG system (its usually got its own 'new' fuse) the car should run okay on petrol, and if not, needs be systematically diagnosed to find what's failing/failed. Once you've got it running fine on petrol, the LPG can be re-initialised. At the moment you seem to have too many variables going on at the same time, which makes specific diagnosis virtually impossible.
Don't LPG cars always start on petrol, then switch to gas? If so, then it's a "petrol side" issue, not a "gas side" issue.

I think the fuel regulator might be letting too much fuel go back to the tank rather than to the injectors... so they could be spraying fresh air, which is obviously a weak mixture and only works when the car is hot. You say you crank it and crank it... but you don't say you noticed a strong petrol smell... so the problem might be a "shortage" of petrol in the fuel rail.

It's interesting that you had two fuel pump failures.. I presume these were second hand pumps, not new new ones? A pump runs all the time once the engine has started, so you can't over-work them. It may be a coincidence that they failed... but I can't think of a problem that makes the pump break and also causes poor starting (usually a weak or failed pump causes the poor starting).

Ralf S.
Don't LPG cars always start on petrol, then switch to gas? If so, then it's a "petrol side" issue, not a "gas side" issue.

Ralf S.

Usually Yes, but also No :unsure: .

Standard starting is on petrol until the temp rises, and then the sensor tells it to switch to LPGs. However there is also the ability to force it onto LPG straight away if you wanted to.

If there's a problem with the LPG system, then it could be going straight onto LPG instead of petrol, or switching between the two, or not working properly on either, hence suggesting to take away the LPG input and concentrate on getting it running on petrol.

That isn't to say all the petrol thoughts and suggestions are not valid :cool: