Fuel Injector: Testing and Inspection

POWER SUPPLY CHECK

1. Disconnect injector harness electrical connector and turn ignition "ON".

2. Check for voltage at the W/R wire terminal of the harness side connector.

IGNITION "OFF" - 0 volts
IGNITION "ON" - 12 volts (battery voltage)

If no voltage is present, check main relay and wiring between main relay and injector harness connector (refer to CHASSIS ELECRTICAL DIAGRAMS).

RESISTANCE CHECK (OFF VEHICLE)

Individual Injector - Resistance Checking:

Check resistance between terminals on individual injectors, as shown in figure.

RESISTANCE......approx. 12 - 16 ohms

If resistance is not within the specified range, replace injector(s).

INJECTOR SPRAY PATTERN AND LEAKAGE CHECKING

NOTE: Before performing any work on the fuel system, relieve fuel system pressure by starting engine with fuel pump relay (circuit open relay) disconnected and let run until engine dies, then slowly and carefully remove hose on outlet side of fuel filter. Cover with a clean rag while removing hose, to avoid spraying fuel in your face.

1. Remove intake manifold dynamic chamber and fuel rail with injectors. Leave fuel lines connected.

Fuel Rail (Delivery Pipe) W/Injectors Attached For Testing:

2. Secure injectors to fuel rail with wire, making certain that injectors are straight and cannot move (see illustration).

Energizing Fuel Pump At Diagnostic Connector:

3. Energize fuel pump by bridging terminals "Fp" and "GND" of the diagnostic test connector, and turning the ignition "ON". See illustration.

4. One at a time, place nozzle end of each injector into a suitable container, and energize injector momentarily by applying power and ground while observing the spray pattern.

^ A finely atomized, cone shaped mist of fuel should spray from the injector nozzle.

WARNING: Fire hazard. Use appropriate connectors and long jumper wires so as not to create any sparks near the injectors or the container of fuel. The mist of fuel sprayed from the injector can ignite very easily.

5. Repeat step 4 for each injector.

6. Dry off injector tips with a clean cloth and check for fuel dripping from injectors. After a minute or so, some wetting or even a drop of fuel seeping from an injector nozzle is acceptable. More than one drip per minute, with the fuel pump running, is unacceptable.

Leaking injectors and injectors with poor spray patterns can sometimes be cleaned, with a chemical fuel system cleaner, and re-used. Use a cleaner designed for fuel injectors. Also some brands of gasoline contain a cleaning additive for fuel injection systems. If clogged or leaking injectors are suspected, switching to one of these brands may help.

If cleaning does not restore normal injector operation, replace the injector(s).