Part 1 of 3
Chart A-3 - Engine Cranks But Won't Run (Part 1 of 3):
Wiring Diagram for Chart A-3 - Engine Cranks But Won't Run:
CHART A-3 - ENGINE CRANKS BUT WON'T RUN (PART 1 OF 3)
Circuit Description:
The C3-I uses a waste spark method of spark distribution. In this type of ignition system, the ignition module triggers the # 1/4 coil pair resulting in both # 1 spark plugs firing at the same time. # 1 cylinder is on the compression stroke at the same time # 4 is on the exhaust stroke, resulting in a lower energy requirement to fire # 4 spark plug. This leaves the remaining high voltage to fire #1 spark plug.
The Sequential Fuel Injection type of fuel delivery system utilizes 6 separate injector driver circuits to activate the 6 fuel injectors. While cranking, the ECM activates all 6 injectors simultaneously (all at one time). After a calibrated engine rpm is reached, and a good Cam signal has been received by the ECM, the injection mode of operation is changed to Sequential (timed separately).
For timing of spark plug firing, a cam sensor "hall effect" switch is used. The cam sensor sends a signal (Sync-Pulse) to the ignition module when cylinder # 1 is 25° after top dead center on the compression stroke. This signal is used to start the correct coil firing sequence and to enable sequential fuel injection. The engine will continue to run if the cam signal is lost while running, however, will not restart after shut down and a Code E041 will be stored.
The crank sensor sends a signal to the ignition module and then to the ECM for reference rpm and crankshaft position. There are three windows in a disc (interruptor) which is mounted to the harmonic balancer. These windows pass by the sensor and as each window passess, the next coil is triggered.
Test Description (Cont'd): The following numbered steps correspond with the step numbers on the diagnostic chart.
1. Identification of "TYPE I" or "TYPE II" ignition system is very important, because the "TYPE I" diagnostics will not work on "TYPE II" systems. Identification can be made by comparing the position of the coil towers with the drawing at the top of the chart. This step verifies "SES" light operation, TPS, and Coolant Sensor signals are normal. A blinking injector test light verifies that the ECM is monitoring the C3-I reference signal and attempting to activate the injectors.
2. Both the Cam and Crank Sensors have been verified as functioning properly, as is evidenced by the blinking injector test light. A fuel pressure test, at this point, will separate the diagnostic path into either a fuel related fault or ignition system malfunction.
3. The 8 terminal injector harness connector must be disconnected to avoid flooding of the engine and fouling of the spark plugs. By testing for spark on plug leads 1, 3 and 5, each ignition coil's ability to produce at least 25,000 volts is verified.
4. By testing the problem coil's control circuit with a test light, a determination can be made as to the problem coil being faulty or the module's internal driver for that coil being the source of the complaint.
5. An injector with a resistance value of less than 10 ohms (shorted) could cause repeat ECM failures.
6. Tests for battery voltage on CKT 839. If voltage was present, the "light off" test result was caused by no activation pulse reaching the injector connector from the ECM.