Fluctuating neg. to ground on ignition coil

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Yes... the cam question dropped to the bottom of my list when the OP showed the smooth operation in his latest video. But valvetrain-related is something like erratically sticking valves.
 
nm9stheham said:
Since you are working on this, OP. Measure all the resistances of the spark plug wires. They should typically be in the range of 3000 to 6000 ohms and none should be over 10000 ohms. And check spark plugs for tight caps on the upper ends, and firm seating. How new are the plugs?
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Measured all the spark plug wires today, got between 11000 and 12000 Ohm except for the short one between the ignition coil and the distributor cap that got around 5000 Ohm.

Spark plug wires are Accel radio suppression wires 8 mm.
20200621_141309.jpg
 
That is higher than I usually allow. I find them more commonly to be in the 5000 ohm range, + or -, for the main wires, when new.

I see this link that discusses spark plug wire resistance in some detail. It indicates that your resistance range is OK, but I never run with them with that high resistance. Usually when they get that high in resistance, they are getting a bit old. SPARK PLUG WIRES

The whole purpose of the resistance is to slow the rate of the current rise the spark, to suppress radio and electronics interference. But too much resistance, then the spark energy gets suppressed so much that it may or may not fire the mixture. This is somewhat suspicious with your idling miss....especially as it occurs with heat.

What spark plug model are you using? And to what distance is the gap set?
 
Got in touch with an old collegue that is an electronics freak, so he will bring his oscilloscope today and try to do some measurements.

Any input on what to look for would be appreciated.

I suppose it´s the secondary pattern that could be interesting?
 
512Stroker said:
Here read this it should help
Spark plug reading can be complex and sometimes frustrating task this page will help make it easier and the results rewarding
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Oh, that was interesting!

I had no idea that much could be read from the spark plugs.

I had the valve seals replaced this spring as it was smoking blue at warm up after sitting a couple of days.

Not sure if the new seals solved the problem as it still smokes at warm up, maybe there was old oil left since before the valve seal replacement?

So today I took the little Mopar for a spin on the highway, with a lot of full throttle accelerations up to 5000 RPM, it smoked at first but later there was not a trace of smoke when I pushed the throttle hard.

Removed spark plugs and took some pictures, it´s hard to get the colours right, but the plugs are very clean after this run and the colour is sort of grey-ish, with some changes at the ground strap bend, see pictures and inserted arrows below.

I'm still not sure of what I see, still confused but on a higher level.
Tänsdtift 2.jpg
Tänsdtift 1.jpg
Tänsdtift 3.jpg
 
Stephan D said:
Oh, that was interesting!

I had no idea that much could be read from the spark plugs.

I had the valve seals replaced this spring as it was smoking blue at warm up after sitting a couple of days.

Not sure if the new seals solved the problem as it still smokes at warm up, maybe there was old oil left since before the valve seal replacement?

So today I took the little Mopar for a spin on the highway, with a lot of full throttle accelerations up to 5000 RPM, it smoked at first but later there was not a trace of smoke when I pushed the throttle hard.

Removed spark plugs and took some pictures, it´s hard to get the colours right, but the plugs are very clean after this run and the colour is sort of grey-ish, with some changes at the ground strap bend, see pictures and inserted arrows below.

I'm still not sure of what I see, still confused but on a higher level.
View attachment 1715553989 View attachment 1715553990 View attachment 1715553991
Click to expand...
Nice. I am glad you liked the information.
Yes sparks can tell you a lot about your engine
Reading the plugs is the key to tuning any engine.
The timing on the plugs is very correct - don't change.
Air fuel ratio looks lean.
Need to have more regular driving miles to get an accurate reading.
Drive the car at normal speeds for 100 miles and read the plugs again.
Good luck
 
67Dart273 said:
Try to find some local amateur radio operators, and if one of them doesn't have a scope, they may lead to other electronics oriented folks
Click to expand...

Finally got in touch with a friend and his oscilloscope, not sure of what we found out.

Can anyone interpret these graphs?

Tried on a single spark plug wire on cylinder 1, looked like this:

cylinder1.png


Wire from the ignition coil, it seems to differ a lot between the pulses to each cylinder:

Spole.png


Spole5.png
 
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