Such a heated discussion...

But the few facts remain-
... fuel pump ...
... ignition system ...
... ECU ...
- won't operate without voltage.
- AND -
... the rotor in the alternator, though being electromagnetic, will itself retain some magnetism without power applied and can generate some voltage if spun fast enough. Whether that is enough voltage for the rotor to self-excite is up for debate and may depend on the age of the alternator and how often it's been operated.
Given that, there are a few conditions that must be met... there must be enough residual fuel pressure in the system or the fuel pump must get enough power to supply sufficient pressure to allow the injectors to inject some fuel with the pulse given by the ECU which itself is drawing power to operate both itself and the injectors while the igniter and coil has to be getting enough power to create spark of sufficient energy to ignite the fuel mixture in the cylinders. The fuel pump, ECU and igniter / ignition circuits are all separate but interdependent.
If the alternator / charging system is otherwise operating properly, this would not necessarily be a problem if the alternator's rotor can be spun up to sufficient speed to meet the minimum current and voltage requirements of all the systems.

Considering this, an electrical system in good condition should be able to bump start if done properly. A compromised system won't. So saying that "mine does" and "mine doesn't" isn't in any way indicitave of all systems.

It just means "some do" and "some don't" and you can't apply that as a blanket statement that either "all should" or "none should".

 

Okay, I will bow to that knowledge... so simple, yet so genious.

 

Very good points...I have just never heard of alternators self exciting that's all. I mean in normal operating conditions if you unplug the exciting circuit from the alternator it will not put out charge. I know that they self excite after they have been initially charged but I don't completely understand how regulators work on a circuit level.

I know an EFI vehicle should never be run without a battery in place however. The battery acts as a voltage stabiliser, without it ECUs can be easily damaged by voltage spikes.