APPEARANCE:; Spark plugs fouled, by <MMT
(Methycyclppentadlenyl
1
JMaganeseTrlcarbonyl)
^kve reddish, rusty appearance on the insulator
...and'sidefelectrode, " , CAUSE: MMTjs.an
anti-knock additive in gaso-line^ used
ip
replace
lead. During the combus-tidn process, the M MT
leaves a reddish deposit
,on
the Insulator and
side electrode., RECqMMENpAtlQN:«No engine
malfunction is Indicated,and the deposits will
not,affect plug . performance any, more
thanlead, deposits (see /\
sn
Deposits), MJMj!
fouled pl(jgs,can'be .Gleaned^egappedand-
reinstalled:','•' ',
; Ash (Lead) Deposits
. , APPEARANCE: Ash deposits are characterized,
'- by,» ifght brown-or.white'colored deposits
,/crusted^qn', the-side "or .center/electrodes.. In
some cases it may'giye the pluga rusty appear-
";arj6a" y'' ' ' '" %
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CAUSEfAsh deposits'are normally derived from
'oil, or fuel additives burned during normal com-
oustion. Nprmally they are harmless, though
' • .expessive amolints cafi cause misfiring. If
de-
' posits
arte
pxcesslye in short mileage, the valve
'guides may toe wprhi^'
•
t
REC'olv|MENDAf ION: Ash-fouierfplugs.can be
f
'.clea^^d/pappedand'reinstalled. .;^ ''
Photos Courtesy Champion Sp^rk Plug Co.
High Speed Glazing
;
APPEARANCE: Glazing appears as
H
shiny<coat"
ing
on
the plug, either yellow 'or tan In color.";
CAUSE: During hard, fast- acceleration, -plug
temperatures rise suddenly. Deposits from nor
mal combustion have no ctiance Jo fluff-off; li> i
stead, they, melt on the insulator, forming .£(h
electrically conductive coating wh,ich ;causes
-misfiring. -,
, ' ,
* ', ^ "^ '- ' , ,
RECOMMENDATION: Glazed p'l'ugsare nbte^s
£
ily; cleaned, ,-th^y' should
l
b,e .-replaced '-.With'^a
fresh"set of plugs of'the correct riealrarigeSlf
the co'nciitiqh^recurs, using.'plug's with!a',h
f
eat'
range one step colder may, bure/the problem:'",
'*'
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t
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f
'
Detonation
APPEARANCE: Detonation'is usual ly/crjafeqj '
te,rized ,by'a brpken plug insulator.. ,>,,•• .f-,ff J'
• CAUSE: A portion of the fueLcharge.w'ill, begin>
to,burn spontaneously, from the increased jieaf-
following, ignition. The explosion that, rpsulis-
.applies, extreme pressureio engine/compo
nents, frequently -damaging spark plugs/and ,
pistons.
1
' , '
- , " '
', \ >,
f
; - '
Detonation can result by dyer-advan,ced igni-
' tiori timing,- inferior gasoline (low octane) lean
air/fueL mixture,, poor carburetion, e.hgine, lug
ging or an in'crease in compressiiori ratio due^o '
combustion chamber deposits or engine modi- „
fication. - ; .,',
, , '
!
- ' '«
V
J' ;
, RECOMMENDATION: Replace'
1
the, plugs?after
1
'
correcting the problem.- ,
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t
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