Fuel Injector: Testing and Inspection
***UPDATED BY TSB #F00193, JANUARY 11, 1993OPERATION CHECK
1. Warm up engine and run at idle.
2. Listen for "click" at each injector with a screwdriver or stethoscope.
3. If engine will not start and no "click" is heard while cranking, check resistance at each injector. It should be 12 - 16 ohms.
4. If injector resistance is okay, check wiring between injectors and ECU terminals 2A, 2U, and 2V. Repair any open or shorted wires.
5. Check voltages at ECU terminals 2A, 2U, and 2V:
a. 2A is an ECU ground and should read 0V.
b. 2U and 2V are injector grounds through the ECU. If always 0V, check the main relay. Also check for open or short circuit between injectors and terminals 2U and 2V. A reading that is always 12V indicates an ECU malfunction. For further ECU troubleshooting information, refer to COMPUTERS AND CONTROL SYSTEMS.
RESISTANCE CHECK
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).
SPRAY PATTERN AND LEAKAGE CHECK
Injector Leakage Check (1):
1. Remove air valve from dynamic chamber.
2. Carefully wire each injector to fuel rail as shown.
3. Disconnect electrical connectors and remove injector/fuel rail assembly with fuel hoses still attached.
Injector Leakage Check (2):
4. Connect a jumper wire across diagnosis connector terminals "F/P" and "GND." Turn ignition switch "ON."
5. One at a time, place nozzle end of each injector into a suitable container, and apply power and ground to energize injector, 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. Mist of fuel sprayed from the injector can ignite very easily.
6. Repeat step 4 for each injector.
7. 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).