K 1500 Truck 4WD V8-305 5.0L VIN M SFI (1996)
Fuel Injector: Description and Operation
Injector And Poppet Nozzle Assembly
DESCRIPTION
Each fuel injector assembly is a solenoid-operated device, controlled by the VCM. The fuel injector assembly meters the pressurized fuel through a
poppet nozzle (5) to a single engine cylinder. The VCM energizes the injector solenoid, which opens an armature valve (3), allowing fuel to flow past the
ball valve and through a fuel tube (1) to the poppet nozzle.
An increase in fuel pressure causes the poppet nozzle ball to open from its seat 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 (4) 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 (2). The extension spring also checks the pressure between the ball and
seat and the injector armature and fuel tube shutoff.
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. These components are diagnosed in The Injector Balance Test and The Injector Coil Test. Refer to Fuel Injector Balance Test. Refer
to System Diagnosis / Diagnostic Tables. See: Computers and Control Systems/Testing and Inspection
