All of the Omega petrol engines use an electronically controlled fuel injection system, a key component of this is the fuel injector it self.

Although the principal of operation of the fuel injector is fairly simple, the part is actually a very high precision item which should be handled with care.




Fuel is supplied to the injector from the fuel rail, this is simply a piece of pipe or box section which contains high pressure fuel (2-3Bar) which is supplied by the fuel pump. The pressure in the rail is maintained by the fuel pressure regulator (can be found mounted onto the fuel rail often with a vacuum connection to allow pressure adjustment dependent on engine load).

By supplying current to the solenoid section of the fuel injector the plunger opens and the fuel is allowed to spray from the spray nozzle. The spray nozzle does two things

1) It atomizes the fuel which ensures it mixes well with the air and allow more complete combustion to occur.

2) In the case of the ECOTEC engines, it sprays onto the back of the hot inlet valve which also aids atomization.

Given that the fuel is of a known pressure, its possible to deliver an exact quantity into the cylinder by varying the length of time that the fuel injector is allowed to open for. This is often referred to as the period or pulse.

The ECOTEC units all use a system called "SFI" (Sequential Fuel Injection) this uses a single injector per cylinder, and traditionally injects fuel immediately upstream of the intake valves just as they are opening.

In order for SFI to work it must know which cylinder is on the intake stroke, this information is supplied by the cam sensor. If the cam sensor fails, the ECU will adopt a limp home mode where all injectors are pulsed simultaneously and the revs are subsequently limited.

Things to note.

Due to the injectors being simply solenoids, its not unusual to hear a light ticking noise from them.

If poor quality or contaminated fuel is used then the injectors can clog and the spray pattern can be affected (unusual on the Omega!), regular fuel filter changes should help to prevent this.