only one black spark plug

[HSV472]

ok about 2 mounts ago i blew the head gasket but befor that my passenger side last plug was always coming out black all fixed now but my spark plug keeps coming out black

its not oil on it its black carbon
what would cause this?

 

[Vt-Brrrlina]

according to the gregories manual

black plugs can be caused by excessive oil consumption or incorect plug type
also says plugs in this condition are generally not firing

spark plug with burnt electrodes due to incorect plug type loose plug or engine running to hot

cracked plugs from age or using to much force

 

[HSV472]

ah ok
could a bad /old rotor cap cause this(only one plug)
or a bad injector?

 

[Vt-Brrrlina]

have fun changin that ive had massive probs with mine as of late and im pretty sure the rotor was the problem - but damn gettn that dizzy cap off......

 

[vn calais manual]

id be leaning towards be a dodgey injector.

and/or lead.

 

[greenacc]

could be a leaking valve stem seal on that cylinder , or piston rings perhaps ? Does it burn much oil ?

 

[HSV472]

doesnt burn any oil at all
also the leads are new and still doing it

 

[greenfoam]

I had dodgy injectors do this a couple of times. I just throw the injector from the rich cylinder away and put another one in

 

[Cheap6]

I had dodgy injectors do this a couple of times. I just throw the injector from the rich cylinder away and put another one in

Might be worth swapping the sus. injector with another cylinder and see if the Carbon'ed up 'plug tracks the injector first though.

 

[savage1987]

if you do need to do the rotor I wrote a how-to on it.. should be able to find it in that section somewhere..


edit: found it
https://forums.justcommodores.com.au/threads/5l-efi-changing-distributor-cap-rotor.62806