Solenoids were applied to fuel injection in 1913. To this day, physics still limits their force and speed.

Relatively weak and slow, the solenoid is confined to operating a servo valve in the injector.
  • The servo valve in turn directs fuel pressure to only open or close the injector needle.
The solenoid and servo valve cause significant, and now unacceptable, time delays.

The solenoid and servo valve confine injector operation to open or closed.

Very finely tuned for some speed, operation is then sensitive to fuel properties.