Fuel Injector: Description and Operation

Fig. 1 Fuel Injector:

FUEL INJECTORS
The fuel injectors are 12 ohm electrical solenoids (Fig. 1). The injector contains a pintle that closes off an orifice at the nozzle end. When electric current is supplied to the injector, the armature and needle move a short distance against a spring, allowing fuel to flow out the orifice. Because the fuel is under high pressure, a fine spray is developed in the shape of a hollow cone. The spraying action atomizes the fuel, adding it to the air entering the combustion chamber. The injectors are positioned in the intake manifold.

The injectors are positioned in the intake manifold with the nozzle ends directly above the intake valve port.

The Auto Shutdown (ASD) relay supplies battery voltage to the injectors. The PCM controls the ground paths to the injectors. By switching the ground paths on and off; the PCM can fine-tune injector pulse width. Injector pulse width refers to the amount of time an injector operates. The PCM operates all injectors.

The PCM determines injector synchronization from the camshaft position sensor and crankshaft position sensor inputs. The PCM grounds the ASD and fuel pump relays after receiving the camshaft position sensor and crankshaft position sensor inputs.

The PCM energizes the injectors in a sequential order during all engine operating conditions.

CIRCUIT OPERATION
Power for the fuel injectors is supplied on circuit A142 when the contacts in the Automatic Shut Down (ASD) relay are CLOSED. Battery voltage for the contact side is supplied on circuit A14. This circuit is HOT at all times and protected by a 20 amp fuse located in cavity 15 of the Power Distribution Center (PDC).

Power for the coil side of the ASD relay is supplied on circuit F12. This circuit is HOT when the ignition switch is in the START or RUN position. Ground for the coil side of the relay is controlled by the Powertrain Control Module (PCM) on circuit K51.

When the PCM supplies a ground path for circuit K51 the contacts in the ASD relay CLOSE connecting circuits A14 and A142. Circuit A142 powers the fuel injectors and is spliced internal to the PDC to supply an ASD relay energized input to the PCM.

The PCM controls the ground path for the injectors as follows, and each of the circuits connects to the white PCM connector:
- Circuit K11 is the ground circuit for Injector #1. Circuit K11 connects to cavity B4 of the PCM.
- Circuit K12 is the ground circuit for Injector #2. Circuit K12 connects to cavity B15 of the PCM.
- Circuit K13 is the ground circuit for Injector #3. Circuit K13 connects to cavity B5 of the PCM.
- Circuit K14 is the ground circuit for Injector #4. Circuit K14 connects to cavity B16 of the PCM.
- Circuit K38 is the ground circuit for Injector #5. Circuit K38 connects to cavity B6 of the PCM.
- Circuit K58 is the ground circuit for Injector #6. Circuit K58 connects to cavity B12 of the PCM.
- Circuit K26 is the ground circuit for Injector #7. Circuit K26 connects to cavity B2 of the PCM.
- Circuit K28 is the ground circuit for Injector #8. Circuit K28 connects to cavity B13 of the PCM.
- Circuit K5 is the ground circuit for Injector #9. Circuit K5 connects to cavity B3 of the PCM.
- Circuit K8 is the ground circuit for Injector #10. Circuit K8 connects to cavity B14 of the PCM.