Actually,
The fuel injection in your car fires two injectors at a time. You only fire two
cylinders per crankshaft revolution so the electronic injection fires the
applicable cylinders. The injection is referencing various factors about the
engine and has a computer map to compare or reference to. The computer references
rpms, air flow, temp, and of course O2 in the exhaust. These factors all 'tell'
the injection how much fuel to inject just before the intake valve opens. Since
the amount of time before the valve opens is such a small amount of time the
injectors that are going to a cylinder that fires that revolution of the crank
receive their injection of fuel. In other words, the firing order is 1342 so
on the first revolution only cylinder 1 and 3 are fired, on the next revolution
4 and 2 are injected fuel. This is LH injection that I'm describing.

I'm sure some of the other electronic injection systems deal with a cylinder at a time basis but the computing power for that is much greater and since cost is also a factor it was economical at that time to have a computer that fires groups of appropriate cylinders with each revolution.

The system in my car is a different injection which does spray fuel all the time.
It is called K-jet and sprays an appropriate amount of fuel that the cylinder will suck in when the valve opens. This type of system is actually more a mechanical system and doesn't time or pulse the injectors. They are only injector valves.

Hope this helps you. Let me know if you would like me to clarify anything I wrote.
Dave 82 242ti 273k mi.