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ONLY HAS SPARK AS LONG AS THE STARTER IS ENGAGED: This symptom usually indicates a bad trigger or low voltage.


  • 1.

    Connect a spark gap tester to the high-tension leads coming from the distributor cap and set the gap to approximately 7/16”. (Use of a CD Tester is recommended).

  • 2.

    Align the rotor with #1 spark plug wire. Disconnect the trigger wires and connect a jumper wire from the brown trigger terminal to the white trigger terminal.

  • 3.

    Connect another jumper wire to the black trigger terminal turn the ignition switch on. Strike the jumper wire from the black terminal against engine ground – (DO NO HOLD THE JUMPER AGAINST ENGINE GROUND). Only the #1 spark plug wire should fire. If any other spark plug wire has fire, there is a problem in the distributor cap.

  • 4.

    Repeat the test for the other cylinders.


  • 1.

    Check the battery voltage on the red and white terminals of the switch box at high speed, the voltage should be between

    • 12.5

      V and 16V DC. A reading outside this range will damage the CD module. If the readings are abnormal, perform the


voltage drop test described above. Perform a high-speed shutdown and read the spark plugs. Check for water. A crack in the block can cause a high miss at high speed when the water pressure gets high, but a normal shutdown will mask the problem.

Four Cylinder Engines 1970-1971 Engines with 337-4406/337-4411 Ignitions

WARNING: Check the battery voltage at approximately 3500 RPM, MAXIMUM allowable reading is 16 volts and minimum is 12V. Running below 12V or over 16 volts will damage the ignition. Check for loose connections or a bad battery. Maintenance free batteries are NOT recommended for this application.

SERVICE NOTE: Due to problems associated with this system, it is recommended that the system be converted over to a 332- 2986/393-3736 type system. (CDI Electronics offers a conversion kit, P/N – 114-2986K1)

Engine Wiring Connection for Testing Ignition 337-4411 Module


  • 1.

    Clean all battery connections and engine grounds.

  • 2.

    Disconnect the mercury tilt switch and retest. If the ignition works properly, replace the mercury switch.

  • 3.

    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.

  • 4.

    Perform a voltage drop test after the engine is repaired to see if there is a problem with the voltage going to the CD module. At cranking and while the engine is running, use a DC voltmeter and put the black meter lead on the battery POS (+) post and the red meter lead on the positive battery cable at the starter solenoid. Keep the black lead on the battery post and shift the red meter 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 up. For instance, if the meter reads 0.4V until you get to the white terminal and then jumps to 2.3V on the white terminal –this indicates a problem in the key switch, or harness. Repeat the test for the negative battery post by putting the black meter lead on the battery NEG (-) post and the red meter lead on the negative battery cable terminal, then shifting to the engine block, rectifier base and case ground of the CD module.


Mercury Troubleshooting

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