Would not start

[edam]

It cranked but would not start
BUT
I remembered that I had run it for a few seconds 2 days ago
I came in and checked on this forum and found it was the classic answer to start it with my foot on the gas pedal. It eventually started .
After 2 days ??

[embee]

I think you identified the issue. Don't start and run any modern car for just a few seconds.

There are often various adaptive or learning functions within many ECUs which will store or adapt the last values for all sorts of parameters, and running it for a very short time can catch them out. If they don't get enough time and/or cycles it can be possible for the adaption process to not be fulfilled and it can for example revert to a default value, which is often not appropriate for the next starting conditions.
I don't know if the Jazz behaves this way, but certainly other cars I've had do. My old Yaris would be very reluctant to start next morning if I moved it on the drive when partly warm and only ran it for a few seconds. Running it for a bit longer solved the problem.

Always run the engine for at least 30sec, preferably more like 1min and ideally hold the revs up a bit, maybe 2000rpm or so. This does 2 things, it gives it enough run time to be happy and it also helps keep the plugs clean of wet carbon (plug temp is very sensitive to rpm, 2000rpm will help heat them up fairly quickly).

[ColinB]

When I encountered this a few years ago the AA man who rescued me advised that, if I need to move the car slightly, do it by driving round the block.

[Lord Voltermore]

I had a car that started first time, without needing to use  any throttle, for 12 years on its original battery.  Then it started firing up first time  but cutting out after a second or two  unless I used some throttle to keep it running. After a few seconds using some  throttle it would then idle and behave normally for the rest of that trip.  Until the next trip.  . 

I discovered that I had really been pushing my luck with such an old the battery. I was fooled by the fact it still gave over 12volts when at rest and  had enough amps for one short healthy sounding cranking, which up until then invariably started the engine. I then discovered it had very little in reserve and voltages were fluctuating under load.      I think this affected ECU settings.   Once the engine was running the alternator took over, giving 14 volts to keep the ECU happy.  And may explain the advice to let the engine run for 30 seconds or more.      A new battery solved the problem.   

Although this car was a corsa, and a diesel, I think similar  battery gremlins could affect a Petrol Jazz

[madasafish]

Weather is cold/cool.Start a car and the ECU enriches the mixture. Then switch off. Surplus petrol condenses on plugs/cylinder walls and head. As engine is cold, petrol does not evaporate quickly - especially as it is winter.
Try starting again and ECU enriches mixture as engine is cold.
Repeat and engine does not start.

Lots of air needed = full throttle.

I battery is discharged  (lots of short runs?) or elderly, voltage drops. ECU may not work properly  and plugs may not fire well.

So check battery voltage.  Should be 12.5V plus .
Charge battery if needed.

Any 8 years car with low mileages (?)  will likely need a new battery..