'Reading' spark plugs

[Zebedee]

I've just replaced the spark plugs in my 1.9 petrol caravelle as i've absolutely no idea when they were last replaced.

The ground electrodes on all 4 plugs are a sort of rich tea biscuit colour.
I think thats about the colour they should be but can someone please confirm?





They are Bosch WR7DC+ and as its running on LPG so they are gapped to 0.63mm.

[Lollypop]

hi zebedee haynes says greybrown deposits with lightly coated corenose ideally suited to engine and engine in good condition so your looking good,i run an 88 caravelle as well with gas,my plugs are the three pronged type with no setting up needed but im not sure if they make any difference but no probs with themso far.

[kevtherev]

plug colour is only applicable after a high speed run then immediate shut down.
engine at over 3000 rpm for over a mile then switch off and check the plug colour.

they should look like yours

checking plug colour at any other time is pointless.

[shakeystu]

Look good to me, you punting them on.Lol

[kevtherev]

I might add..
Mixture can only be accurately checked on a rolling road.
Your MOT emissions check will give an accurate image of idle speed mixture,
ie. CO ideal 2.5% (rich or leaness) O2 air leaks, HC (hydrocarbons below 400ppm is good) oil leaks and lean rich mix

Lambda at around 1% is ideal

[ghost123uk]

In my experience plug colour checking does not work the same when running on LPG.

The products of combustion are very different from those produced by petrol so you certainly cannot evaluate whether your engine is running rich or lean by looking at the plugs like you can on petrol.

However it will show up any oil burning and yours look fine in that respect

[Zebedee]

Its runs sweetly, idles at a nice steady 850revs, doesn't smoke and has no loss of power. Plus i've saved over £400 in fuel costs even with LPG being 78.9p round here so i'm happy with it.
I was constantly getting one sooted up plug (and an irritating misfire) until i realised there was one plug lead with an end barely held on.

[California Dreamin]

Plugs looks good if you are looking at them conventionally but as others have said LPG is different.
As for triple electrodes (W7DTC), I've run mine on them for a couple of years and convinced myself that they are better (smoother idle/better warm up) but I have to point out that the electrodes are non adjustable and come set at well over 1mm clearance on each tip.
Therefore, It is hard to know whether this has any down sides as in making the coil work harder because of the increased gap, perhaps a weaker less sustained spark even though that spark is larger...who knows!
Standard W7DC plugs were set to 0.7mm
I have read that engines running LPG prefer smaller spark plug gaps...I'm not sure if there is any real science backing this up but 0.6mm on an electronic ignition system does sound a little on the narrow side.
The plugs you are running are pretty decent, possibly the best compromise being the latest incarnation of the original classic W7DC but with modern improvements like a tapered
v-profile nickel chromium ground electrode for better cold starting.

Martin