CDI Electronics Outboard Ignition Troubleshooting Guide

102 TROUBLESHOOTING GUIDE - Mercury Troubleshooting Mercury Troubleshooting NO SPARK OR INTERMITTENT SPARK ON ONE OR MORE CYLINDERS: 1. Check the trigger resistance and DVA output as given below: WIRE READ TO RESISTANCE DVA (Connected) DVA (Disconnected) Purple White 800-1400 4 V + 4 V + (#) Brown White/Black (or Black) 800-1400 4 V + 4 V + (#) Purple Engine GND Open 1 V + N/A White Engine GND Open 1 V + N/A Brown Engine GND Open 1 V + N/A White/Black Engine GND Open 1 V + N/A (#) This reading can be used to determine if a pack has a problem in the triggering circuit. For instance, if you have no spark on one or two cylinders and the trigger’s DVA reading for that cylinder is low – disconnect the trigger wires and recheck the DVA output. If the reading stays low – the trigger is bad. If the reading is now within spec – the pack is bad. (Note) If #1 and #2, or #3 and #4 are misfiring, check the trigger as described above. The trigger has two coils firing four cylinders. #1 & 2 share a trigger coil and #3 & 4 share a trigger coil. Also, the switch box is divided into two parts. The #1 and #2 cylinders spark on one side and #3 and #4 spark from the other side of the switch box. If the trigger tests are okay according to the chart above, but you have two cylinders not firing (either #1 and #2, or #3 and #4), the switch box or stator is bad. 2. If you have two cylinders not firing (either #1 and #2, or #3 and #4), switch the stator leads end to end on the switch box (swap Red with Red/White) and (swap Blue with Blue/White). If the problem moves to the other cylinders, the stator is bad. If the problem stays on the same cylinders, the switch box is likely bad. 3. Check the DVA output on the Green wires from the switch box while connected to the ignition coils. Check the reading on the switch box terminal AND on the ignition coil terminal. You should have a reading of at least 150V or more at both terminals. If the reading is low on one cylinder, disconnect the Green wire from the ignition coil for that cylinder and reconnect it to a load resistor. Retest. If the reading is now good, the ignition coil is likely bad. A continued low reading symptom indicates a bad power pack. 4. If the cylinders are only misfiring above an idle, connect an inductive tachometer to all cylinders and try to isolate the problem cylinders. 5. Check the triggering and charge coil flywheel magnets for cracked, broken and loose magnets. SWITCH BOX 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 switch box. 2. In contrast, a shorted SCR inside the switch box can destroy a trigger coil. Check the trigger resistance and DVA output (see NO SPARK OR INTERMITTENT SPARK ON ONE OR MORE CYLINDERS above). 3. Replace the ignition coil on the cylinder dropping spark. ENGINE WILL NOT SHUT OFF: Disconnect the stop wire at the switch box. Connect a jumper wire to the stop wire from the switch box and short it to engine ground. If this stops the switch box from sparking, the stop circuit has a fault. Check the key switch, harness and shift switch. If this does not stop the switch box from sparking, replace the switch box. Repeat test as necessary for additional switch boxes. WILL NOT ACCELERATE BEYOND 3000-4000 RPM: 1. Disconnect the Yellow wires from the stator to the rectifier and retest. If the engine now has good spark, replace the rectifier. 2. Connect a DVA meter between the stator’s Blue and Blue/White wires. Run the engine up to the RPM where the problem is occurring. DVA voltage should increase with RPM. A sharp drop in DVA right before the problem occurs usually indicates a bad stator. (Read from Blue to engine ground if the engine has a Red stator kit installed). 3. Connect a DVA meter between the stator’s Red and Red/White wires. The DVA voltage should show a smooth climb in voltage and remain high through the RPM range. A reading lower than on the Blue wire reading indicates a bad stator. 4. Connect an inductive tachometer to each cylinder in turn and try to isolate the problem. A single cylinder dropping spark will likely be a bad switch box or ignition coil. All cylinders not sparking properly usually indicates a bad stator. 5. Perform a high-speed shutdown and read the spark plugs. Check for water. A crack in the block can cause a