Fuel Injector: Description and Operation

MPFI Injector - Cross Section:

Primary And Secondary Injector Placement:

DESCRIPTION
The fuel injectors (primary and secondary) are solenoid operated metering valves, controlled by the PCM, that deliver pressurized fuel to a single engine cylinder. The PCM energizes the injector solenoid, which opens a ball valve, allowing fuel to flow past the ball valve, and through a recessed flow director plate. The director plate has six machined holes that control fuel flow, generating a conical spray pattern of finely atomized fuel at the injector tip. Fuel is directed at the intake valve, causing it to become further atomized and vaporized before entering the combustion chamber.

OPERATION
There are 16 injectors, one primary and one secondary injector for each cylinder. Primary injectors are in operation during engine cranking and throughout the engine's operating range. Secondary injectors deliver fuel only when enabled by the PCM, and only during periods of high engine speeds and loads ("FULL" power enrichment mode).

An injector that is stuck partly open would cause loss of pressure after engine shut down. Consequently, long cranking times would be noticed on some engines. Dieseling could also occur because some fuel could be delivered to the engine after the ignition is turned "OFF."

The ball and seat design of the Multec port fuel injectors eliminates the need of ever having to use an injector cleaner. By design, the fuel metering portions of the fuel injector are not exposed directly to the intake manifold gases that are responsible for the build-up of deposits that can cause injector clog.

Some cleaners may contain high percentages of methanol and other solvents that cause damage to the injectors coil wire insulation. Damaged insulation results in low resistance or shorted injectors. Also, high percentages of methanol or other solvents can increase friction at the injectors critical bearing surfaces, resulting in premature wear.