Fuel Injector: Description and Operation

Injector And Poppet Nozzle Assembly:

DESCRIPTION
Each Sequential Fuel Injection (SFI) fuel injector assembly is a solenoid-operated device, controlled by the VCM. The Sequential Fuel Injection (SFI) fuel injector assembly meters the pressurized fuel through a poppet nozzle to a single engine cylinder.

OPERATION
The VCM energizes the injector solenoid, which opens an armature valve (1), allowing fuel to flow past the ball valve and through a fuel tube to the poppet nozzle.

An increase in fuel pressure causes the poppet nozzle ball to open from its seat (2) against the extension spring force. This allows the fuel to flow from the nozzle (at approximately 280 kPa (40 psi)).

De-energizing the injector solenoid closes the armature. De-energizing also reduces the fuel pressure acting on the poppet nozzle ball. The extension spring closes the ball to the seat. The extension spring also checks the pressure between the ball and seat and the injector armature and fuel tube shutoff.

RESULTS OF COMPONENT FAILURE
An injector poppet nozzle that is stuck partly open would cause a loss of pressure after the engine shut down. Consequently, the driver would notice long cranking times on some engines. Dieseling could also occur because the fuel injector could deliver some fuel to the engine after the driver turns the ignition to OFF.

DIAGNOSIS
These components are diagnosed in The Injector Balance Test and The Injector Coil Test.

Refer to Computers and Controls / System Diagnosis / Procedures / Diagnostic Tables / System Diagnostic Tables / Fuel Injector Balance Test and Fuel Injector Coil Test.