ORIGINAL: piper_chuck
ORIGINAL: britbrat
ORIGINAL: Mohney
Not sure why it would fowl a glow plug.
If it contains any halogenated compounds it could poison the platinum catalyst. I don't know if there are any halogens present in WD-40.
They weren't listed in the ingredients when this was discussed.
Maybe it doesn't foul glow-plugs. Are there any metallic compounds in the ingredients? That could do it as well.