CDI Electronics Outboard Ignition Troubleshooting Guide

95 Mercury Troubleshooting Mercury engine. 5. Check the flywheel magnets for cracked, broken and loose magnets. NO SPARK OR INTERMITTENT SPARK ON ONE CYLINDER: 1. Check the flywheel magnets for cracked, broken and loose magnets. 2. Check the trigger resistance and DVA output: WIRE READ TO OEM RESISTANCE CDI RESISTANCE DVA (Connected) DVA (Disconnected) Brown/Yellow Brown/White 750-1400 700-800 4 V + 4 V + (#) Brown/Yellow Engine GND Open Open 1 V + N/A Brown/White Engine GND Open 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 cylinder 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. 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 places. 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 indicates a bad switch box. 4. Check the ignition coil’s primary resistance from the Positive (+) Terminal to the Negative (-) Terminal. You should read 0.02-0.04 ohms. 5. Check the ignition coil’s secondary resistance from the sparkplug wire to engine ground. You should read 800- 1.1K ohms. If out of this range, replace the ignition coil. 6. Connect an inductive tachometer to each cylinder and compare the RPM readings at the RPM where the problem is occurring. If only one cylinder is dropping out, swap the ignition coil locations and retest. If the problem follows a coil, replace the coil. If it stays on the same spark plug, replace the switch box. 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 CYLINDER above). 3. Replace the ignition coil on the cylinder dropping spark. ENGINE WILL NOT SHUT OFF: Disconnect the Black/Yellow stop wire at the switch box. Connect a jumper wire to the Black/Yellow stop terminal (or 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 and harness. If this does not stop the switch box from sparking, replace the switch box. WILL NOT ACCELERATE BEYOND 3000-4000 RPM: 1. Connect a DVA meter between the stator’s Black/Yellow wire/terminal and engine ground. 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. 2. Connect a DVA meter between the stator’s Black/White wire/terminal and engine ground. The DVA voltage should show a smooth climb in voltage and remain high through the RPM range. A reading lower than on the Black/Yellow wire/terminal reading indicates a bad stator. 3. 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. 4. 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. 5. Check the flywheel magnets for cracked, broken and loose magnets. 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. In the water or on a Dynameters, check the DVA output on the Green wires from the switch box while connected