fishsurfer
Cadet
- Joined
- Oct 28, 2014
- Messages
- 16
I have a 20HP Mercury 1990 that is misfiring intermittently. Its starts first pull everytime and has 115psi on both cylinders. I measured 0.762k and 3.2k for the trigger and stator coils and replaced the spark plugs. I don't have a DVA but have a Fluke 124 scopemeter and took a few shots so hopefully someone can spot something. It looks like all parts are firing as required and I even used a Colortune spark plug to verify the spark and mix for both cylinders. I'm thinking a faulty coil pack. Any ideas would be a great help.
Pics are
1) Stator coil output
2) Switch box output not connected to the coils
3) One switch box output vs stator coil pulses. The switch box pulses follow the stator pulses for this cylinder. The other cylinder is the same.
4) Trigger coil output
5) Alternating switch box output pulses for both cylinders. No missing pulses.
All these are taken with spark plugs out and pulling the cord. Misfire happens idling and revved.
Pics are
1) Stator coil output
2) Switch box output not connected to the coils
3) One switch box output vs stator coil pulses. The switch box pulses follow the stator pulses for this cylinder. The other cylinder is the same.
4) Trigger coil output
5) Alternating switch box output pulses for both cylinders. No missing pulses.
All these are taken with spark plugs out and pulling the cord. Misfire happens idling and revved.