CDI Electronics Outboard Ignition Troubleshooting Guide

114 TROUBLESHOOTING GUIDE - Mercury Troubleshooting Mercury Troubleshooting 4. Disconnect the CDM modules one at a time and see if you get spark back on the problem cylinders. If it does, replace all CDMs. 5. If the cylinders are only misfiring above an idle, connect an inductive RPM meter to all cylinders and try to isolate the problem cylinders. 6. Check the resistance of each of the CDM modules (see NO SPARK ON ANY CYLINDER above). CDM OR TRIGGER REPEATEDLY BLOWS ON SAME CYLINDER: 1. Check the trigger wires for shorts to engine ground as a shorted trigger wire can destroy a SCR inside the CDM. 2. In contrast, a shorted SCR inside the CDM can destroy a trigger coil. Check the trigger resistance and DVA output (see NO SPARK ON ANY CYLINDER above). 3. Cut the Black/Yellow stop wire from the CDM not sparking. Measure DC voltage from Black/Yellow (from the harness) to engine ground. Turn the ignition switch on and off several times. DC voltage should never exceed 2V. If it does, the stop circuit has a fault. Check the key switch, harness and shift switch. 4. Replace the CDM on the cylinder dropping spark. MISS AT ANY RPM: 1. Disconnect the Yellow wires from the stator to the rectifier and retest. If the miss clears, replace the rectifier. 2. Connect an inductive tachometer to each cylinder in turn and try to isolate the problem. A high variance in RPM on one cylinder usually indicates a problem in the trigger or CDM module. Check the trigger DVA voltage (see NO SPARK OR INTERMITTENT SPARK ON ONE OR MORE CYLINDERS above). 3. Perform a high-speed shutdown and read the spark plugs. Check for water. A crack in the block can cause a miss at high speed when the water pressure gets high, but a normal shutdown will mask the problem. 4. Check the triggering and charge coil flywheel magnets for cracked, broken and loose magnets. 5. Rotate the stator one bolt hole in either direction and retest. 6. Index the flywheel and check the timing on ALL cylinders. On carbureted models, the control module rev limit function starts to retard timing in sequence (2, 3, 4, 5, 6, 1) at 5800-6000 RPM. The control module will retard the timing each cylinder up to 30 degrees (starting with #2) and then stop firing that cylinder if the RPM is still above the limit. It will continue to retard, then shut down each cylinder until the engine drops below the limit. NO SPARK OR INTERMITTENT SPARK ON #1, #2 and #3 OR #4, #5 and #6 CYLINDERS: 1. Check the cranking RPM. A cranking speed less than 250-RPM will not allow the system to spark properly. 2. Disconnect the CDM modules one at a time and see if you get spark back on the problem cylinders. 3. Check the stator resistance and DVA output as given below: WIRE READ TO OEM RESISTANCE CDI RESISTANCE DVA (Connected) DVA (Disconnected) White/Green Green/White 380-430 380-430 160-400 V 200-400 V (*) White/Green Engine GND Open Open 160-400 V < 2 V Green/White Engine GND Open Open 160-400 V < 2 V (*) This reading can be used to determine if a stator or the CDM modules have a problem. For instance, if you have no spark on any cylinder and the stator’s DVA reading is low – disconnect the stator wires and recheck the DVA output. If the reading stays low – the stator is bad. If the reading is now within spec – at least one of the CDM modules is bad. 4. Check the trigger resistance and DVA output (see NO SPARK OR INTERMITTENT SPARK ON ONE OR MORE CYLINDERS above). 5. Check the trigger DVA output as given below: WIRE READ TO RESISTANCE DVA (Connected) Purple Engine GND Open 0.2 to 2V White Engine GND Open 0.2 to 2V Brown Engine GND Open 0.2 to 2V Blue Engine GND Open 0.2 to 2V Red Engine GND Open 0.2 to 2V Yellow Engine GND Open 0.2 to 2V 6. If (#1, #2 and #3) or (#4, #5 and #6) is not sparking, swap the White/Green and Green/White stator wires and