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:
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 and # 4 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 remainding 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 seperately).
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 sequence of coil firing 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 wil 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 passes, 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 II" diagnostics will not work on "TYPE I" 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. The blinking injector test light verifies a working Cam Sensor. A fuel pressure test, at this point, will seperate 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. An erratic spark may be an indication of an open secondary winding in one of the ignition coils. This can result in internal arcing which may seek ground through the C3-I module resulting in a stall or "Cranks But Won't Run" condition.
4. By switching the problem coil with a working one, 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 639. If voltage was present, the "light off" resulted from the injector not receiving an pulse from the ECM.