Fuel Injector: Testing and Inspection
Injectors - On Car Electrical Checking:
POWER SUPPLY CHECK
1. Disconnect injector harness electrical connector.
2. Check for voltage at the B/Y 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 ELECTRICAL DIAGRAMS).
INJECTOR RESISTANCE CHECK (ON VEHICLE)
Injectors - On Car Electrical Checking:
With injector harness disconnected, check resistance between terminals of the injector side of connector with wire colors as shown in diagram.
INJECTORS #1 & #3
Check between terminals B/Y & LG/R
INJECTORS #2 & #4
Check between terminals B/Y & LG/B
RESISTANCE (BOTH TESTS)....6 - 8 ohms
NOTE: This test checks the resistance of injector pairs connected in parallel. The resistance through the circuit is always less than the smallest resistance in the pair. If the measured circuit resistance is greater than 8 ohms, but less than approx. 16 ohms, then one injector has an open. If this is the case, test the injectors individually to find which one is faulty. If the measured circuit resistance is greater than 16 ohms, both injectors in the pair are faulty, or there is an open in the wiring between the connector and the injectors.
Individual Injector - Resistance Checking:
INJECTOR RESISTANCE CHECK (OFF VEHICLE)
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, LEAKAGE AND VOLUME 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.
Leak Checking Fuel Injectors:
2. Secure injectors to fuel rail with wire, making certain that injectors are straight and cannot move (see illustration).
Fuel Pump Test Connector:
3. Energize fuel pump by bridging the terminals of the yellow 2 pin test connector (located near the air cleaner box) and turning the ignition "ON". See illustration
4. One at a time, place nozzle end of each injector into a suitable measuring container, and apply power and ground to energize injector for 15 seconds, while observing the spray pattern.
^ A finely atomized, cone shaped mist of fuel should spray from the injector nozzle. Note volume of fuel collected in container.
2.5 - 3.0 ozs (74 - 89 cc)
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 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).