Re: S.L.O.W. symptoms without slow powerpack
Inside of the potting on the rectifier are a group of diodes. Normally, failure of the diodes for any of the reasons that you are familiar with prevents the rectifier from performing normally.
Too often, when the diodes fail, they generate enough heat to melt the potting and fuse the wires from the several diodes, allowing the battery voltage to flow to the ignition or to heat the potting in the rectifier to the point of ignition.
It is the precise reason that the troubleshooting instructions from various sites list disconnecting the rectifier as one of the first tests when there is no spark.
See CDI Electronics
Troubleshooting Guide:
"
"Four Cylinder Engines
NO SPARK ON ANY CYLINDER:
[FONT=Times New Roman,Times New Roman](Note: If the engine has spark with the spark plugs out but not with them installed, the timer base is either weak or the engine is not spinning fast enough. See # 6 and #8.) [/FONT]
[FONT=Times New Roman,Times New Roman]1. Disconnect the black yellow stop wire and retest. If the engines' ignition now has spark, the stop circuit has a fault-possibly the key switch, harness or shift switch. [/FONT]
[FONT=Times New Roman,Times New Roman]2. Disconnect the yellow wires from the rectifier and retest. If the engine has spark, replace the rectifier. [/FONT]
[FONT=Times New Roman,Times New Roman]3. Check the stator resistance. You should read about 500 ohms from the brown wire to the brown/yellow wire. [/FONT]
[FONT=Times New Roman,Times New Roman]4. Check the DVA output from the stator. You should have a reading of at least 150V or more from the brown wire to the brown/yellow wire (while connected to the pack). [/FONT]
[FONT=Times New Roman,Times New Roman]5. Check the timer base resistance from the #1 to the #3 sensor wire, and from the #2 to the #4 sensor wire. Reading should be 10-20 ohms on each set (or 30-40 ohms for CDI Electronics Blue Timer Bases). [/FONT]
[FONT=Times New Roman,Times New Roman]6. Check the DVA output from the timer base. A reading of at least 0.5V or more from the #1 sensor wire to the #3 sensor wire, and from the #2 sensor wire to the #4 sensor wire (while connected to the pack) is needed to fire the pack. If the output is low, you may try to reset the air gap between the timer base sensor and the triggering magnet using a Sensor Gap Gauge (553-9702) or use the following procedure: [/FONT]
[FONT=Times New Roman,Times New Roman]a) Loosen the two mounting screws on the sensors and the nuts located in the epoxy on the outside of the heat shield of the timer base. [/FONT]
[FONT=Times New Roman,Times New Roman]b) Slide the sensors in toward the crankshaft until the sensor touches the stop boss located at the base of the sensor mounting area. Tighten the mounting screws. [/FONT]
[FONT=Times New Roman,Times New Roman]c) Coat the face of the sensors with machinists bluing or equivalent. [/FONT]
[FONT=Times New Roman,Times New Roman]d) Install the flywheel without the key and rotate the flywheel at least one full turn. [/FONT]
[FONT=Times New Roman,Times New Roman]e) Remove the flywheel and check to see if the trigging magnet struck the face of the sensors. If it did, back the sensor out approximately 0.005" and repeat steps c, d and e. [/FONT]
[FONT=Times New Roman,Times New Roman]f) If the ignition fired, finger tight the nuts on the outside of the heat shield and coat them with RTV. [/FONT]
[FONT=Times New Roman,Times New Roman]g) If still no fire, replace the sensor. [/FONT]
[FONT=Times New Roman,Times New Roman]7. Check the DVA voltage on each black/white wire to engine ground. You should have a reading of at least 150V or more (while connected to the pack). If the reading is low, disconnect the trigger wires from the pack and recheck the black/white terminals on the pack. If the voltage jumps up to an acceptable reading, the timer base may have a problem in the internal wiring (possibly a thin spot in the insulation on one wire). [/FONT]
[FONT=Times New Roman,Times New Roman]8. Check the cranking RPM. A cranking speed of less than 250-RPM will not allow the system to fire properly. "[/FONT]
