That would make sense that the engine only runs on one bank, and doesn't set any fault codes. Shutting it off and restarting might get the relay working and it will then run on all eight cylinders. How did you diagnose it? Was the problem sporadic, or did it happen on a regular enough basis so that you could track down the cause?
It might have set a code if the relay coil had failed. The Motronic ECU controls the relay coil. The ECUs seem to monitor the coil circuits of at least some of these relays. Interestingly, the left bank fuel pump Speed 1 relay coil circuit is in parallel with part of the Evap Test Pump circuit. Issues with the Evap Test Pump have been known to cause a Fuel Pump "B" fault message. Counter-intuitively, fuel pump "B" seems to be the Speed 1 pump.
Page 125 or 126 in the owner's manual for the rest of the Left Side Passenger Compartment relay-fuse descriptions. The cool/cold start issue on this 2008 430 Scuderia ( a friend's car) was always intermittent. The local Ferrari dealership guessed at an oxygen sensor issue and replaced one. That did not correct the problem. When the start problem did happen, my friend had to shut off engine and wait maybe ten minutes then start engine again. The engine either operated normally or he had to repeat the wait then start process. We looked for similar issues with other F430 and 430 Scuderia and associated solution, but did not find an exact match. My friend thought maybe; voltage too low, a loose electrical connection, Ignition ECU issue, a fuse, or a relay issue. When the failures occurred he did not smell unburned fuel from the left cylinder bank exhaust. When the ECUs checked out he moved on to fuses and relays.
When I purchased my 2009 430 Scuderia in 2015 I noticed a cold start issue. When started, it would idle roughly and not at a higher cold idle I would expect. If I shut off and immediately restarted, it was fine, idling smoothly and faster. It would do this about every other cold start...perhaps every third cold start. I mentioned it to Ferrari of Seattle and the service manager Eric mentioned there was a software update they could perform to correct this. I had them do it, (it was very inexpensive at the time, perhaps $125 labor) and it never recurred after the update. That was 10 years ago.
