spark plug check

[omega_rugal]

today i got some free time to work on the MJ, and pulled the spark plugs, 2 thru 5 were clean, they had a thin layer of carbon but could be scratched off easily, below the electrodes were good and whiteish in color... but 1 and 6... they had more carbon build up, it burns lpg so is not gasoline related, all the plugs were dry so is not oil or water getting on the combustion chamber, any ideas? dust?

[jdog]

have you changed them since it was converted to lpg?

how many miles on the plugs?

how much more build up?

[omega_rugal]

i changed them a month or 2 before the conversion, that was 4 years ago, so almost all of their life have been running on lpg, miles?  id unno, the odometer broke long ago

 

carbon buildup in 2-5 was almost non existant, only 1 and 6 had some but nothing that prevented them from firing, it was just there

 

now that i think of it, 1 and 6 are in the opposite sides of the engine, all lpg comes from the throttle body, no fancy multipoint injection, unequal air fuel ratio? if so, shouldn´t the outer cylinders get the LEANER mix? 

[jdog]

I would say probably uneaqual air/fuel mixture as to why they aren't showing lean you have got me, maybe its only lean during certain times, ie full throttle or high revs

[cruiser54]

Make sure the intake manifold bolts aren't loose.

[omega_rugal]

the intake feels solid, no loose bolts/nuts, i checked for vacuum leaks today and found none, took out 1 and 6 and they look as clean as yesterday so it may be a long term problem...

 

Quote

maybe its only lean during certain times, ie full throttle or high revs

 

due the way my lpg system is rigged, this may be it, thrttole response is a little slow, that may be the lean phase it´s causing trouble...

[jdog]

hows the egr system? hoping thats all it was, and they stay nice and clean for ya

[omega_rugal]

no egr