Outboard Ignition Troubleshooting – Page 17 – Mercury Battery CD Ignitions Without Points
This page covers Mercury three cylinder battery-powered CD ignition systems without points, including 332-4796 and 393-4797 type ignitions. These procedures cover no spark, intermittent spark, trigger testing, distributor checks, and high-speed miss diagnosis.
Mercury Battery CD Ignitions without Points
Three Cylinder Engines
332-4796 / 393-4797 Type Ignitions
Three Cylinder Engines
332-4796 / 393-4797 Type Ignitions
Service Note: Check battery voltage at approximately 3500 RPM. Maximum allowable reading is 16 volts and minimum is 12 volts. Running below 12V or above 16V can damage the ignition. Check for loose connections or a bad battery. Maintenance-free batteries are not recommended for this application.
General
- Clean all battery connections and engine grounds.
- Disconnect the mercury tilt switch and retest. If the ignition works properly, replace the mercury switch.
- Connect a spark gap tester to the spark plug wires and check for fire on all cylinders. If some cylinders fire and not others, the problem is likely in the distributor cap, rotor button, or spark plug wires.
- Perform a voltage drop test after the engine is repaired to verify there is not a voltage supply problem to the CD module. At cranking and while the engine is running, use a DC voltmeter and put the black lead on the battery positive post and the red lead on the positive battery cable at the starter solenoid. Keep the black lead on the battery post and move the red lead to the positive post of the rectifier, then to the red and white terminals on the switch box. If you find a reading above 0.6V, there is a problem at the point where the voltage jumped. Repeat the test on the negative side by placing the black lead on the battery negative post and the red lead on the negative cable terminal, then moving to engine block, rectifier base, and case ground of the CD module.
No Fire at All
- Connect a spark gap tester to the high-tension lead coming from the ignition coil and set it to approximately 7/16". If it fires there but not through the spark plug wires, there is a problem in the distributor cap, rotor button, or spark plug wires.
- Check DC voltage present on the white and red terminals while cranking. It must be at least 9.5 volts. If not, there is a problem in the harness, key switch, starter battery cables, or battery.
- Check DC voltage on the white/black trigger terminal while cranking. There must be at least 9V available with the trigger wire connected.
- Check DVA voltage between the blue and black trigger wires while they remain connected to the switch box. You should read at least 3V. A low reading indicates a bad trigger.
- Check DVA voltage on the green wire going to the coil. It should be over 100 volts at cranking.
Only Fires When You Let Off of the Keyswitch
- This symptom usually indicates a bad trigger or low voltage.
No Fire or Intermittent on One Cylinder
- Connect a spark gap tester to the high-tension leads coming from the distributor cap and set the gap to approximately 7/16".
- Align the rotor with the #1 spark plug wire. Disconnect the trigger wires and connect a jumper wire from the white/black trigger terminal to the black trigger terminal on the switch box.
- Connect another jumper wire to the blue trigger terminal, turn the ignition switch on, and strike the jumper wire from the blue terminal against engine ground. Do not hold it against ground. Only the #1 spark plug wire should fire. If another spark plug wire fires, there is a problem in the distributor cap.
- Repeat the test for the other cylinders.
High Speed Miss
- Check battery voltage on the red and white terminals of the switch box at high speed. Voltage should be between 12.5V and 16V DC. A reading outside this range can damage the CD module. If the reading is abnormal, perform the voltage drop test described above.