Injection Quantity, Leak and Spray Pattern Test

NOTE: Before attempting this test, make sure that the fuel system pressure is to specifications. If incorrect fuel pressure is suspected, perform FUEL SYSTEM PRESSURE TEST first.

1. Remove electrical connector(s) from fuel injector(s).
2. Remove the fuel rail with injectors from the intake manifold.

Bridging System Relay:

3. Turn ignition OFF.
4. To start fuel pump, remove the [1][2]system relay (located in center console behind ash tray) and seat belt reminder relay.
5. Connect a lead between terminals 30 and 87/2 and between 30 and 85 on relay base. The fuel pump should start operating. Check by listening to the pump. Pump can be heard by removing the tank cap. If fuel pump does not run, see FUEL PUMP(S).

Bridging Suppressor Relay:

6. Disconnect suppressor relay located in front of coolant expansion tank.
7. Bridge terminals 3 and 4 of relay base.
8. Check (at each injector connector) for the one terminal with current.
9. Connect a test lead between that terminal and its connection at the injector.
10. Connect a lead between ground and the other terminal at one injector. Injector will now start operating.
11. Use a fuel resistant clear container to catch the fuel.

Spray Pattern Test:

12. Check the spray pattern of the injector.
A poor spray pattern can cause the following problems:

^ Hard starting and stalling when cold
^ Restart problems after short trips
^ Poor coold driveability
^ Rough idle
^ Backfiring on acceleration
^ Combustion knock
^ Surging at cruise speed
^ Dieseling

If a poor spray pattern is observed, use an industry approved fuel injector cleaning system and perform cleaning process as instructed by cleaner manufacturer. When done, recheck spray pattern.
If fuel injector pattern is very poor, replace and retest with new injector.

NOTE: On vehicles with high milage, it is recommended to replace the fuel injectors in sets. This may save you diagnosis time an the other injectors that could fail shortly after replacement of the first bad injector.

13. Use a fuel resistant measuring cup and meter the volume of fuel injected over a one minute period.

Volume: approx. 170 cc/min at correct system pressure of 43 psi (300 kPa)

If reading is different, replace and retest with new injector.
14. Disconnect injector jumper wire to ground.
15. Clean tip of injector immediately and check for injector leakage.

Leakage: less than two drops per minute at tip

If leakage exceeds two drops per minute, replace and retest with new injector.
16. Repeat steps 10 through 15 on all remaining fuel injectors.
17. Disconnect all jumper wires, reinstall all relays and the fuel rail with injector(s) (use new seals if needed).