All Small Six Diagnosing with air/fuel meter

[DON]

I can definitely understand grounds with points type system

 

[Frank]

I can definitely understand grounds with points type system

Actually the electronic ignitions would be more susceptible to distributor body-to-block ground fault unless they are otherwise grounded. Matter of amperage- more amps will push through resistance more. Original points, all the amperage for the coil is going through the points, grounding via the breaker plate, into the distributor body, into the block. My points with the TFI module, the points have to ground 12 milliamps. Any corrosion or oily interference with that weak signal ground, it's broken. I don't know how the magnetic pickup signal is "closed", but it's not much of a signal in amps, relative to factory points.

 

[pmuller9]

I don't know how the magnetic pickup signal is "closed", but it's not much of a signal in amps, relative to factory points.

The signal generated by a pickup coil and reluctor alternates polarity and is not connected to ground in any way.

 

[Frank]

The signal generated by a pickup coil and reluctor alternates polarity and is not connected to ground in any way.

10-4! Thanks for that.

 

[DON]

The signal generated by a pickup coil and reluctor alternates polarity and is not connected to ground in any way.

So grounding in the distributor is not a factor with the MSD distributor, correct?
That was my thought to begin with.
I checked resistance in the existing pickup coil and a new one, there was 1 ohm difference. It was 587 and 588

 

[vssman]

Did you try wiggling the wires while you measured resistance?

 

[pmuller9]

So grounding in the distributor is not a factor with the MSD distributor, correct?

That is correct.
Check both leads coming from the distributor with an ohm meter and there should not be any continuity to ground

 

[DON]

I didn’t check to ground, but I will. I would think if it was grounded it wouldn’t function at all. I didn’t purposely move wires but I can do that as well. The terminals are out of the housing. The ohms were stable

 

[drag-200stang]

At this point I would put in a points dist. and coil. to rule out the MSD combo.
PS, do not lose the oil pump drive.

 

[DON]

How about a 4 prong module to start with?

 

[Frank]

How about a 4 prong module to start with?

sounds logical. Been pleased with the magnetic dist (DS2) and GM module in one truck, flawless for some time now.

 

[DON]

My thought is to do one thing at a time, then I will know what it was. I am really starting to think about a faulty item. The only thing that I don’t buy is the symptoms are exactly the same

 

[drag-200stang]

My thought is start back to good old points system and see what happens and then go from there.

 

[DON]

I think my original dizzy has petronix. It’s been a long time. I will have to look

 

[DON]

I do I’d recheck the ohms on the pulse generator, it was stable when wires were moved, and checked both wires to ground

 

[DON]

Update: problem solved. Short story, a float valve was stuck shut. Replaced bowel assembly, with new float, valves ( bowels were already on the list to replace). Ran like a top. Just got back from an hr ride.
Details on troubleshooting. I was talking with my buddy, retired, life time mechanic. He was going to bring over some sort of scope, digital I think. I got to taking with him in detail about problem, and fuel came around. I had just gone thru the carbs within the last 6 mths, set idle with O2 meter, checked float levels. After talking with him, I kept thinking about fuel, so next day I pulled float level plugs and sure enough, one float wasn’t floating, smacked the bowel a couple times, jiggled the float and in came the gas. New bowels are on, adjusted, runs great.
Thank you all for the input. I was baffled but it was a learning experience. I have learned a lot about MSD ignition.
And when diagnosing, have an open mind!!

 

[drag-200stang]

Does anyone remember my saying. ''If you think it is ignition related it will be air/fuel related, and if you think that it is air/fuel it will be ignition". Every time.

 

[DON]

You have been studying Murphy’s law!

 

[Bill1958]

Update: problem solved. Short story, a float valve was stuck shut. Replaced bowel assembly, with new float, valves ( bowels were already on the list to replace). Ran like a top. Just got back from an hr ride.
Details on troubleshooting. I was talking with my buddy, retired, life time mechanic. He was going to bring over some sort of scope, digital I think. I got to taking with him in detail about problem, and fuel came around. I had just gone thru the carbs within the last 6 mths, set idle with O2 meter, checked float levels. After talking with him, I kept thinking about fuel, so next day I pulled float level plugs and sure enough, one float wasn’t floating, smacked the bowel a couple times, jiggled the float and in came the gas. New bowels are on, adjusted, runs great.
Thank you all for the input. I was baffled but it was a learning experience. I have learned a lot about MSD ignition.
And when diagnosing, have an open mind!!

"And when diagnosing, have an open mind!!"
Great job..."having an open mind" and your tenacity got you to the finish line...along with all the great input from the pit crew here.
I wouldn't have thought of a stuck float valve...I'll have to remember that one...and my own name