Chart 6C-3 Injector Flow/Resistance Check

INJECTOR FLOW/RESISTANCE CHECK (CHART 6C-3)















DESCRIPTION:
The Injector Flow/Resistance Check compares the fuel pressure drop when each injector is pulsed for a set amount of time. Since each injector is pulsed the same, the fuel pressure drop for each injector should be approximately the same. Suspect fuel injectors can be identified by either too high or too low fuel pressure drop. This check also determines if the resistance of the injectors is within specification. Injector resistance out of specification can cause driveability conditions that are intermittent or that do not show up during an injector flow check. This chart requires J 34730-1 Fuel Pressure Gage and J 39200 voltmeter

NOTES ON FAULT TREE:
1. Selecting P505 for 5 seconds will energize the fuel pump to build fuel pressure. Then selecting individual injectors with P510 will allow you to seethe fuel pressure drop associated with each injector. If all eight injectors drop some pressure then the circuit is not open. Any injector that drops no pressure has an open in the circuit or faulty injector.
2. Checking if a fuse was open causing either injectors 2, 3, 5 and 8 or 1, 4, 6 and 7 not to operate.
3. Checking if CKT 481 or CKT 482 is open from the fuse to C102,
4. Check injector resistance at the engine temperature when the condition occurs. Injector resistance will normally increase with increasing temperature. Faulty injectors may measure OK cold, but not hot. Normally injector resistance should be between 8 and 25 ohms.
5. If injector resistance is normal but the injector flow pressure drop was not within 2 psi of the other injectors, replace that injector.
6. Checking for a short in the fuel rail harness or a shorted injector.
7. Checking for an open or high resistance in the fuel rail harness or an open or high resistance injector.
8. Checking for an open or high resistance inside the intake manifold.
9. Checking for an open or high resistance injector.
10. Checking for an open between C128 and the PCM or a faulty PCM that is causing the injector not to operate.
11. Checking for open or high resistance injector circuit.
12. Checking for open between S136/S137 and fuel injector.
13. Checking for shorted fuel injector. Injector resistance should be checked at the temperature the condition occurs. Faulty injectors may measure OK cold, but not hot. Normally, injector resistance is between 8 and 25 ohms.
14. Checking for open or high resistance injector.
15. Checking for faulty PCM or open injector control circuit.