Re: 1973 50 Hp Johnson no spark
From the CDI Troublshooting Guide:
Two Cylinder Engines
NO SPARK ON EITHER CYLINDER:
1. Disconnect the black yellow stop wire and retest. If the engine's ignition has spark, the stop circuit has a fault-check the key switch, harness and shift switch.
2. Check the stator resistance. You should read approximately 500 ohms from the brown wire to engine ground.
3. Check the DVA output from the stator. You should have a reading of at least 150V or more from the brown wire to engine ground (while connected to the pack).
4. Check the timer base?s resistance from the black/white wire to the white/black wire. Reading should be 10-20 ohms (or 30-40 ohms for CDI Electronics 133-0875K1). Note: The original factory specifications was 8-14 ohms, this was changed around the mid 1970?s in response to the change in SCR?s triggering requirements.
5. Check the DVA output from the timer base. A reading of at least 0.5V or more from the black/white wire to the white/black (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.
a. Loosen the two mounting screws on the sensor and the nut located in the epoxy on the outside of the heat shield of the timer base.
b. Slide the sensor in toward the crankshaft approximately 0.005? at a time.
c. Coat the face of the sensor with machinists bluing or equivalent.
d. Install the flywheel according to the service manual and crank the engine over.
e. Remove the flywheel and check to see if the trigging magnet struck the sensor face.
f. If the ignition fired, finger tight the nut on the outside of the heat shield and coat it with RTV.
7. If still no fire, slide the sensor in another 0.005? and repeat steps c through f.
6. Check the DVA voltage on each trigger wire to engine ground. You should have a reading of at least 150V or more from the black/white wire and the white/black wire to engine ground (while connected to the pack). If the reading is low, disconnect the trigger wires from the pack and recheck the terminals on the pack. If the voltage jumps up to an acceptable reading, the timer base may have a problem in it?s internal wiring (A thin spot in the insulation on one wire).
7. Check the cranking RPM. A cranking speed of less than 250-RPM will not allow the system to spark properly.
