I run an 07 late Mk 1 1.4 petrol Fabia, which intermittently won’t start when the external air temperature is up in the 20C+ range. Always starts immediately usually and shows no fault codes at all. Seems mixture related as it smells ‘petrolly’ when it happens. Green Flag showed us a get-round which works every time it plays up by holding the accelerator down and turning the ignition off and then on. It's only an intermittent fault.

Any clues anyone please? Car’s well maintained and done 5K miles since its last service incl new spark plugs.

Possible coolant temp sensor.

Any update on this, some people in warmer places than UK have found that the EVAP solenoid can cause this issue, maybe sounds a bit strange but seems to be true - in a few cases.

Got a new original Skoda sensor today and plan to fit it this weekend. This process alone has sent the hot weather

 packing! Will update once I have info to report.

 

Thanks for the constructive help in both the posts above.

Fitted the new sensor earlier today - it was the 2-terminal type. Not a hot day today and it started and re-started fine afterwards. My wife drove it later too on a routine journey and without any prompt said the car feels smoother. The tickover is more even, noticeable at the first start-up after fitting, and it feels more responsive generally to drive. Filled it up with fuel to see if the MPG improves in the days ahead, as it may well have been running generally richer than it should. Main fault was the poor restart on hot days so may not get a proper check on this happening for a while. Well, it is summer  

Good!  

Now that you have included "restart" in hot weather it 99.9% pointed to the ECT sensor and not the occasional EVAP solenoid that I suggested as an outside possibility.

This can be where a fully compliant VW Group scan tool helps, okay if the ECT sensor is not handing the correct temperature but a credible/possible one, no fault will get logged, but you could have been able to see what the ECT sensor thought the temperature was - and worked out if that was correct or not.