Just put the engine back in my 2015 3W after a clutch change. It's been stood in the garage with no battery for around 4 months but I have added more fresh fuel than was left in the tank - so I don't THINK ts fuel.
It appears to be consistent.. Runs for around 1 min and then slows slightly then coughs, splutters and quits. If you start it again it runs for around 20 seconds and does the same - so appears to be heat related. Done 50,000 miles with all the usual mods including a new fuel pump at 20,000 miles, drive coupling upgraded etc etc
https://youtu.be/l15L0_i_2HESo far I have checked and changed:
Crank sensor
Coil pack
Ignition leads
Fuel pressure (52PSI and steady)
No errors in the ECU
Does the same without the air cleaner
The cam belt hasn't been touched.
I have heated the ECU before I start it and it doesn't make any difference. It was a bit colder this morning and it ran a bit longer so its def temp related. It has been suggested it might be the inlet manifold seals which I will change next.
Just throwing it out there for any ideas.. Failing that its going on eBay CHEAP
Many thanks
Dave