Originally Posted by
speedracerntrixie
I agree that it could be too rich on the bottom end but I have seen either a plug being bad out of the package or if an engine has been sitting for a while it can have rust on any of the steel internals. Rust particles will take out a plug very quickly.
Can you tell us how rust particles can take out a glow plug in a 4-cycle engine? I can't say I've heard of the valves rusting, but I suppose that'd be the only possibility?