Spark Plug Color - LJet
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Spark Plug Color - LJet
Hello world! (New owner, first post)
What color are the spark plug insulators normally on a LJet engine?
I have spent the last few weeks since purchase replacing the FPRs, o-rings, all sensors, switches, and vacuum/oil hoses. Initially it ran over-rich, but after removing the PO's resistor on the temp sensor, it runs great, no pinging, but the plugs are white.
Shouldn't the color be light-brown?
(I had an adapter fabbed to put a VDO gauge on the fuel rail; ~29psi at idle, >35psi at shutoff.)
What color are the spark plug insulators normally on a LJet engine?
I have spent the last few weeks since purchase replacing the FPRs, o-rings, all sensors, switches, and vacuum/oil hoses. Initially it ran over-rich, but after removing the PO's resistor on the temp sensor, it runs great, no pinging, but the plugs are white.
Shouldn't the color be light-brown?
(I had an adapter fabbed to put a VDO gauge on the fuel rail; ~29psi at idle, >35psi at shutoff.)
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Hello "PorKen",
The plug color on my old 81 928 were mostly white,
though 4 and 8 were a little darker.
Here are some photos:
Plugs 1-4
Plugs 5-8
The plugs on my 90 were about the same.
George
The plug color on my old 81 928 were mostly white,
though 4 and 8 were a little darker.
Here are some photos:
Plugs 1-4
Plugs 5-8
The plugs on my 90 were about the same.
George
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From: Ball Ground, GA
Spark plug color is not a very good indicator of anything anymore on a properly-running street engine in the USA - unless you have an extreme condition.
The plug color is now determined largely by the brand of fuel - the different companies use different trace additives in the fuel, and these are the primary determinants of color now.
Back in the old days, you had lead in the fuel, which created snow-white deposits. A rich fuel mix sould make a dry black deposit, oil in the cylinder would make a wet black deposit. The color you got was mainly a blend of these.
The lead is long gone. Most engines run very lean by the old standards, so there is very, very little fuel deposit. Most 928s have little oil in the cylinders, thanks to the almost-perfect cylinder wall surfaces.
The remaining deposits are mostly a very little oil, plus the fuel scavengers and other additives. These deposits may be almost any color, although tan to brown seems to be the most common. I have seen green, yellow, orange, white, black, etc., etc.
The plug color is now determined largely by the brand of fuel - the different companies use different trace additives in the fuel, and these are the primary determinants of color now.
Back in the old days, you had lead in the fuel, which created snow-white deposits. A rich fuel mix sould make a dry black deposit, oil in the cylinder would make a wet black deposit. The color you got was mainly a blend of these.
The lead is long gone. Most engines run very lean by the old standards, so there is very, very little fuel deposit. Most 928s have little oil in the cylinders, thanks to the almost-perfect cylinder wall surfaces.
The remaining deposits are mostly a very little oil, plus the fuel scavengers and other additives. These deposits may be almost any color, although tan to brown seems to be the most common. I have seen green, yellow, orange, white, black, etc., etc.
