K-jet 450 missing when stopped in drive

[ptashek]

What will a fouled plug look like, and do they just need cleaned or replaced?  I might just wait until I can buy a whole new set of plugs.

Plenty of soot, or soot+oil "paste" build-up around and on the electrode would be a typical indicator. If the electrode hasn't deteriorated much (doesn't look corroded/pitted/burned out), it usually is fine to just carefully wire-brush all the carbon deposits off. Check and re-set the electrode gap afterwards too (I think it should be either 0.8 or 0.7mm).

[jbrasile]

Casey,

I second everyone else's opinion to the problem being electrical in nature. Once you rule out wires, cap/rotor/plugs, a bad coil will do exactly what you describe, had this happen with  the green 6.9 we restored as well as my own 78 450. Try a coil from one of your other cars just for fun, it is easy enough to change them around. Original Blue Coils from Bosch are NLA, replacements are silver with a red sticker and made in Brazil, sometimes NOS blue ones do show up on e-bay.

Tks,

Joe

[Casey]

I second everyone else's opinion to the problem being electrical in nature. Once you rule out wires, cap/rotor/plugs, a bad coil will do exactly what you describe, had this happen with  the green 6.9 we restored as well as my own 78 450. Try a coil from one of your other cars just for fun, it is easy enough to change them around. Original Blue Coils from Bosch are NLA, replacements are silver with a red sticker and made in Brazil, sometimes NOS blue ones do show up on e-bay.

I have no idea what/where the coil even is.  Still quite new to gas engines.

[ptashek]

I have no idea what/where the coil even is.  Still quite new to gas engines.

Facing the windshield it should be in the front right corner of the engine bay, beside and slighlty up from the headlamp assembly. The coil looks like this:

[oversize]

Jeez if you don't know what a coil is should you be buying a 6.9?   

[Casey]

Jeez if you don't know what a coil is should you be buying a 6.9?   

I've been driving diesel Mercedes' exclusively for the last decade, just got some 450's this year and haven't had a lot of need to tinker on them much.  You don't learn things by avoiding them.    There's no engine repair knowledge standard required for purchasing a 6.9...would you rather I just remain ignorant rather than learning?