Chart A-3 Engine Cranks But Won't Run (VIN 7)
CHART A-3
(Page 1 of 3)
ENGINE CRANKS BUT WON'T RUN 1986-1987 3.8L TURBO (VIN 7) (PORT)
Circuit Description:
The C(3)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 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).
CHART A-3(Page 1 of 3) ENGINE CRANKS BUT WON'T RUN 1986-1987 3.8L TURBO (VIN 7) (PORT):
Test Description: Step numbers refer to step numbers on diagnostic chart.
1. 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 C(3)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) must be replaced.
6. Tests for battery voltage on CKT 639. If voltage was present, the "light off" test result was caused by no activation pulse reaching the injector connector from the ECM.
CHART A-3
(Page 2 of 3)
ENGINE CRANKS BUT WON'T RUN 1986-1987 3.8L TURBO (VIN 7) (PORT)
Circuit Description:
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 to the ignition module (CKT 633) is lost, however, will not restart after shut down and a Code 41 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. As these windows pass by the sensor, the next coil is triggered.
CHART A-3(Page 2 of 3) ENGINE CRANKS BUT WON'T RUN 1986-1987 3.8L TURBO (VIN 7) (PORT):
Test Description: Step numbers refer to step numbers on diagnostic chart.
7. Verifies ignition feed voltage at terminal "P" of the C(3)I module. Less than battery voltage would be an indication of a CKT 439 fault.
8. The test light to 12 volts simulates a reference signal to the ECM which will result in an injector test light blink. This test validates CKT 430, the ECM and the injector driver circuits.
9. If the Cam Sensor signal circuit, terminal "B", is momentarily jumpered to the ground circuit, terminal "C", and the engine is cranked without
turning the ignition switch "OFF", the response should be an injector test light blink. This is a result of the artificial "Cam Signal" being transmitted through the C(3)I module to ECM terminal "All" and the ECM activating the injector driver circuit.
10. Verifies a proper Cam signal circuit voltage of 6 to 9 volts and a good ground from the C(3)I module to terminal "C" of the sensor connector.
11. Determines if the incorrect voltage reading was due to a fault in CKT 633, an open in CKT 632 or a faulty C(3)I module.
CHART A-3
(Page 3 of 3)
ENGINE CRANKS BUT WON'T RUN 1986-1987 3.8L TURBO (VIN 7) (PORT)
Circuit Description:
For timing of spark plug firing, a cam "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 to the ignition module (CKT 633) is lost, however, will not restart after shut down and a Code 41 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. As these windows pass by the sensor, the next coil is triggered.
CHART A-3(Page 3 of 3) ENGINE CRANKS BUT WON'T RUN1986-1987 3.8L TURBO (VIN 7) (PORT):
Test Description: Step numbers refer to step numbers on diagnostic chart.
12. Jumpering the Crank Sensor harness terminals "B" and "C" together simulates a Cam signal to the C(3)I module. Then, by repeatedly jumping the Crank sensor harness terminals "B" and "C" together a Crank signal is simulated which should result in the injector test light blinking.
13. Verifies a proper Crank signal circuit voltage of 6 to 9 volts and a good ground from the C(3)I module to terminal "B" of the sensor connector.
14. Determines if the incorrect voltage reading was due to a fault in CKT 643, an open in CKT 642 or a faulty C(3)I module.