Spark Plug Wear

[FJ4013]

Rig: 1978 FJ40 2F

This is my first time changing out the spark plugs in 3K miles. To the guys here who have had FJ40s for awhile is there any story these plugs are telling you? They are in order as they were pulled from left to right. The front plug has hardened whiteish soot which according to the manual means it might be running hot. The irony is it runs cool or at least at normal temps. I never have any overheating issues.

Any feedback is welcomed.

FWIW these are NGK plugs after approximately 3,000 miles. I just replaced them with Denso W14EXR-U (3013)

NGK Plugs - 3K Miles

• FJ4013
• Aug 23, 2018

 

[thebigredrocker]

By hot, they probably mean lean. Cool would be rich or fat.

What jets are you running? Pretty sure there are a few threads on mud that discuss re-jetting a 79 Aisan.

 

[FJ4013]

By hot, they probably mean lean. Cool would be rich or fat.

What jets are you running? Pretty sure there are a few threads on mud that discuss re-jetting a 79 Aisan.

I have a Weber 38 carb so assuming they are Weber jets.

 

[45Kevin]

Definitely running lean.
But that might also be a timing issue or your valves are not set to spec.

The one on the left appears to be OK. That would suggest a valve issue.

 

[Tancruiser]

That crusty one looks like oil burning to me.

 

[FJ4013]

That crusty one looks like oil burning to me.

Shoot. I should have mentioned a few months back I did have an issue where I was burning oil. The cylinders were honed and the piston rings were replaced and the oil burning went away. I barely added any oil the past 3K miles. I do not recall if the shop who did the cylinder job and piston rings replaced the spark plugs or not so we may be looking at the set that was in before the work was done. That would explain the oil burning look. Otherwise as she runs right now she burns no oil at all.

 

[SteveH]

I see minor oil contamination - likely from valve stem seals, in my experience. Nothing to worry about, IMO.