Spark plugs: light fouling with white ash - what is the cause?

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P

Polo

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Take a look at the photo that shows my daily driver (3/79 2F-federal smog) plugs with 1000mi on them. The plugs are lightly fouled with a hard white ash.

Is this a result of oil? All my nearby gas stations only sell 10% ethanol… is that it?

Thanks in advance for any info and comments.

Gordon

PlugsWith1000mi.webp
 
Looks like lean mixture to me. Mine burns oil and the plugs look like they got dipped in ashes and soot, very messy. Yours looks good and and clean, just to hot. Bigger primary main jet would be a good start.
 
Those plugs are certainly not oil fouled--I don't see any black, oily gunk on any of them. They almost look like the normal tan that good combustion should produce. Doesn't look like any abnormal electrode wear either. maybe a lean mix on the fuel, but-----Are you having engine missing issues that caused you to check the plugs? or is this just your normal periodic checkup?--if just a checkup--regap-reinstall-and wheel on-----
(Make sure plug temp range is correct)
 
Lean burn for sure
 
I did some reading about oxygenated fuel (ethanol) and it sounds like it is as simple as increasing the fuel in the air/fuel ratio by at least the percentage of ethanol in your fuel. That would be 10% for most of us. So increase primary main jet hole size by 10%?
 
Thanks for the info, I appreciate your responses.

The white ash builds up pretty quickly. I actually purchased one of these:

http://www.harborfreight.com/pneumatic-spark-plug-cleaner-32860.html

I blast clean the plugs about every three months or so... I drive 500 to 800 miles per month.

Not sure of jet size... it's a stock Aisin carb ... rebuilt by JimC about 12 yrs ago. Can I adjust the carb rather than change the jet?

Gordon
 
Only adjustments are for idle speed and idle mixture. You would have to change jets. I think you are fine, and no need to clean the plugs so often. Drive and enjoy the the ride.
 
That type of spark plug cleaner was all the rage about 20 years ago. The problem with them is that they tend to round off the sharp edges on the electrodes that the plug designers work so hard to design. Arcs like to jump from sharp edges. That's why the iridium plugs have a serrated tip and a 'U' shaped ground electrode. Just physics.
 
The whitish ash I dont beleive is a result of a lean fuel mixture. To me, it looks like a result of some sort of fuel additive. Fuel additives that leave a whitish residue makes the plug look like its running lean when it might not be
 
The whitish ash I dont beleive is a result of a lean fuel mixture. To me, it looks like a result of some sort of fuel additive. Fuel additives that leave a whitish residue makes the plug look like its running lean when it might not be
 
melvinjo said:
The whitish ash I dont beleive is a result of a lean fuel mixture. To me, it looks like a result of some sort of fuel additive. Fuel additives that leave a whitish residue makes the plug look like its running lean when it might not be
Click to expand...

My experience also. To the OP, either stop putting gas additive in your tank, or change brands of gasoline.
 
I think that is ash from light oil use, perhaps from tired valve stem seals. My FJ40 plugs look like this, but somewhat worse. Not all oil-burning trucks leave huge sooty deposits on the plugs. I would do nothing about this, except reinstall the plugs and drive it.
 
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