Black spark plugs

[anonymous-user]

Number 3 wasn't firing and I had a black and wet spark plug.

I've changed the soark plug and it's firing again on all 4.

The other 3 plugs were new. They are now black. Why?

Engine is on 45 carbs with a webcom aplha ECU.

Thx

[andyiley]

Either running too rich, or you did not run the engine long enough to get it "off the choke".

[paintman]

Is the fouling oil or excessive fuel?
Have a look at this:
http://www.gnttype.org/techarea/engine/plugs.html
and this from NGK:
http://ngksparkplugs.com/tech_support/spark_plugs/...

[anonymous-user]

It doesn't have a choke but I'm thinking the fact I've been struggling to Start it (due to one dud plug) the whole thing might have been a bit fuelly and flooded might explain it.

I've ordered some new plugs so I'll have a fesh set to go on.

The old ones (that were in up until recently) looked healthy after prolonged use and the carbs haven't been adjusted at all recently.

[paintman]

Possible that you've had a plug fail - had that a couple of times over the years.
Look on the bright side, you've only got 4 to worry about. Mine's a V8........

[anonymous-user]

Definitely a plug has failed. I changed back to an old one that I had taken out and it's running nicely.

Question is, why are the other 3 black? I think it's probably because there was so much fuel going in trying to start it up.

[littleredrooster]

The only way to assess the mixture using plug colour is to do a proper 'plug chop'. The engine needs to be up to working temp and held, under load, at a steady largish throttle opening then cut the ignition, declutch and stop. The colour of the plugs at that point can give an indication of what's happening inside.

Pulling plugs out after a period of idling or stop-start will not tell you anything useful, other than if a cylinder is not firing at all.

[Boosted LS1]

Plug chops are only really useful when under load etc. They don't help with cranking or idle conditions. If the plug has over fuelled it'll stink of petrol and be wet. If there's excess oil from the rings or valve guides the engine will smoke and the intake/exhaust ports will be oily.

[anonymous-user]

Thx for the replies gents.

I'm confident it's running well now. I'm in the process of putting it back together.

I'll report back if I have any more issues.

[anonymous-user]

..To complete this thread. It turned out to be the coil pack. It was on its way out but hadn't quite failed. Changed it and the car was happy as larry again.

[trickywoo]

I'd change the engine oil due to possible contamination with fuel.