Spark plugs indicate lean mix on carbureted V6

What happens is when the main metering is lean is as you accelerate from a stop and that will cause a drop in vacuum sufficient to open the powervalve. then as you get going the vacuum comes up and the valve closes that causes the engine to go lean which produces less power and a drop in vacuum which causes the valve to open again and then you get a surge of power and then the vacuum comes up and the valve closes again and so on.

No you need something in the fuel to produce the tan color. Modern gasoline is like white gas they used to sell in hardware stores for Coleman stoves. Also, if the engine burns a little oil it will produce some tan on the spark plugs. The alcohol replaces other components that boosted octane and may have contributed some color on the plugs. Add some Marvel Mystery oil to you gas tank - that should help with giving your plugs some color.

Probably you need to go the other way. Lean it out until you actually get some indication it is running lean.

-jim

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Reply to
jim
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LOL! As much as I love the smell of MM Oil, I don't think it is worth the money just to get colorful spark plugs.

I just finished a marathon web search relating to reading plugs. It was a real eye opener. The subtleties involved are more than I realized and the info that I grew up with doesn't always apply today. Most of the sites are related to racing. Here are a couple that I thought were extremely informative, especially for the photos:

Reading Spark Plugs

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Plug Reading - Gas Engines - 4 Stroke
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Spark Plugs
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How might that indication present itself? Plug condition? Rise in coolant temperature? Something else that doesn't cost money in a shop to determine?

Reply to
Jack

Actually, its nothing AT ALL like "white gas" that they used to sell for coleman stoves. "White gas" was pure gasoline with no detergent or antiknock additives which would foul and clog the gas-generator in lanterns or stoves. Modern fuels may not have lead or manganese anymore, but they have a whole witches brew of anti-knock and detergent additives, oxygenates, and vapor-pressure modifiers.

Reply to
Steve

White gas is not pure gasoline. White gas or camp stove gas is almost pure Naphtha. Nevertheless, pump gas is like white gas with respect to the discussion that was on going, which you snipped. The discussion was about why gasoline burns without leaving color on the plugs. He made the point that ethanol cleans the spark plugs. I was suggesting a better way to look at it is the ethanol replaced the stuff that makes the spark plugs tan.

But now that you brought it up much of the gas sold in many parts of the country is nothing but the refinery fractions plus ethanol. From what I have read many refineries are meeting the required standard for regular mogas without adding anything other than ethanol to the refined petroleum.

-jim

Reply to
jim

| Plug insulators are still snow white after all | driving conditions. What brand are these plugs ? NGK's insulators ( bigger & so remain hotter ) can stay clean better than Champion / Denso. Your plugs' heat range sounds correct.

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| Any suggestions as to what might be causing this plug condition? I believe insulators cannot get soot in dry air ; I used to drive in

0C dry air using Champion N9Y plugs, & once for 4 hr when thermostat had overstretched & could not close so carb & engine were too cold ( weak & coughing ) in 15C dry air, no soot @ all. Now in 27-32C humid air, I have a soot problem to mitigate.

| Absolutely nothing makes sense. Why worry w-o a problem ? Are you in dry air ? If exhaust has a O2 sensor, 1 can connect a voltmeter & see if mix is lean.

Reply to
TE Chea

Which is tantamount to saying that acetone is like water because both are clear liquids...

I seriously doubt that, although I suppose its possible to barely meet the minimum standards that way since ethanol does have both limited anti-knock and very good detergent properties.

Reply to
Steve

They only need to start with 83 octane straight gas then add 10% ethanol to meet the anti-knock standards. And ethanol is the only oxygenate additive that is now in use. In regard to "barely meeting standards" - the term used by refineries to describe doing anything else is "giveaway".

-jim

Reply to
jinn

For octane, yes. For vapor pressure, detergent function, long-term storage stability, etc.... there are many shades of grey.

Reply to
Steve

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