Fuel Injector: Testing and Inspection
POWER SUPPLY CHECK1. Disconnect electrical connectors from all injectors.
2. Check for voltage at the B/Y wire terminal of the harness side of connector for each injector.
IGNITION "OFF" - 0 volts
IGNITION "ON" - 12 volts (battery voltage)
If no voltage is present with ignition "ON", check main relay and wiring between main relay and injector harness connector (B/Y wire) for open or short to ground. If voltage is present with ignition "OFF", check for faulty main relay or short to power in wiring harness between main relay and injector.
Checking Injector Resistance:
INJECTOR RESISTANCE CHECK
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. On the 929 DOHC V-6 engine, fuel system pressure can also be relieved by gradually and carefully loosening the banjo bolt on the cold start valve (on top of the throttle body). Cover with a clean rag when doing so, to avoid spraying fuel.
1. Remove intake manifolds, dynamic chamber, and fuel rail with injectors. Leave fuel lines connected to fuel rail.
Fuel Rail With Injectors Attached For Testing:
2. Secure injectors to fuel rail with wire, making certain that injectors are straight and cannot move (see illustration).
Jumping Fuel Pump Test Connector:
3. Energize fuel pump by bridging the terminals of the yellow 2 pin test connector and turning the ignition "ON" (connector is located near the air flow sensor). 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 or remote switch, 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 gasolines contain a cleaning additive for fuel injection systems. If clogged or leaking injectors are suspected, switching to one of these gasoline brands may help.
If cleaning does not restore normal injector operation, replace the injector(s).