CDI Electronics Outboard Ignition Troubleshooting Guide

116 TROUBLESHOOTING GUIDE - Mercury Troubleshooting Mercury Troubleshooting Mercury Six Cylinder Engines 1994-2003 225/250 3.0L Engines Using CDM Modules Service Notes: Please use the Factory recommended spark plug (currently Champion QL77CC) gapped at 0.035” for EFI engines and 0.040” for Carbureted engines. The Crank Position Sensor should be gapped at 0.040” +/- 0.020”. The maximum spark timing is controlled by the ignition ECU and is non-adjustable. As long as the ECU, Crank Position Senor and Throttle Position Indicator are functioning properly, the maximum timing will be correct. NO SPARK OR WEAK SPARK ON ANY CYLINDER: 1. Disconnect the Black/Yellow stop wires from the harness. Retest. If the engine’s ignition now has spark, the stop circuit has a fault. Check the key switch, harness and shift switch. 2. Inspect the spark plug wires, boots and spark plugs. Check for chafing on the wiring and harnesses. 3. Inspect and clean all engine and ignition ground connections. 4. Check the Stator Harness for loose connections. 5. Check the Alternator for dragging and shorted diodes. 6. Check the Crank Position Sensor resistance as given below: WIRE READ TO RESISTANCE Red White 900-1300 NO SPARK OR WEAK SPARK ON ONE CYLINDER: 1. Inspect the spark plug wires, boots and spark plugs. Check for chafing on the wiring and harnesses. 2. Clean and inspect CDM ground wire connection to engine ground. 3. If the cylinders are only misfiring above an idle, connect an inductive RPM meter to all cylinders and try to isolate the problem cylinders. 4. Check the Stator resistance and DVA output as given below: WIRE READ TO RESISTANCE DVA (Connected) Green Engine GND 990-1210 100 V + Green/Red Engine GND 990-1210 100 V + Green/Yellow Engine GND 990-1210 100 V + Green/Blue Engine GND 990-1210 100 V + Green/Orange Engine GND 990-1210 100 V + Green/Black Engine GND 990-1210 100 V + 5. Check the resistance of each of the CDM modules as follows: RED METER LEAD BLACK METER LEAD READING CDM Pin # A C 1200-1400 Ohms CDM Pin # D A DIODE* CDM Pin # A D DIODE* CDM Pin # D B DIODE* CDM Pin # B D DIODE* CDM Pin # A B DIODE* High Tension Lead A OEM 700-1300 Ohms – CDI 2200-2400 Ohms * Diode readings are to be read one way, then reverse the leads and read again. You should get a low reading in one direction and a higher reading in the other. TIMING FLUCTUATES: Service Notes: It is normal for timing to fluctuate 2° @ idle. If engine overheats (above 200°F), Engine Temperature Sensor will retard timing to limit RPM to 3000. If engine RPM exceeds 6000, over-rev circuit in ECU will retard timing to reduce RPM. If engine RPM drops below 475, idle stabilizer in ECU will advance timing 3° to 6°. 1. Clean and inspect all ground connections. 2. Check the Crank Position Sensor gap (0.040” +/- 0.020”) and resistance as given below: WIRE READ TO RESISTANCE Red White 900-1300