Modern spark plugs

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peterc
Posts: 1549
Joined: Wed Mar 05, 2014 9:05 am
Location: Surrey

Modern spark plugs

Post by peterc »

Hi guys one and all.
It has been brought to my attention that modern spark plugs no longer have their central core coated to protect them from fuel penetration.
This is fine on a Fuel Injected car as they run so lean but anything with a Carb could have an issue in certain circumstances. e.g. they are easily fouled.
One day the car is running really well and the following day is as rough as hell.
What did I do wrong?
Imagine a couple of dawdling cars that needed despatching, so given a short stretch of dual carriageway I floored the throttle. Because I passed them so quickly I then realised that I was then exceeding the speed limit so throttled off accordingly. It was after this action that the car then ran rough.
The theory being that the engine was loaded up with fuel for the acceleration but because I throttled off so quickly it didn't have a chance to properly use it all thus fouling the plugs.
Numerous other checks were performed with no success until I changed all 8 plugs. Yes, they were sooty, but I had assumed something else was the cause and they would burn clean once the issue was resolved.
I'm sure we have all done something similar to that at some stage and I have never had any issues previously over the two decades I have had he car.
I don't know when they chose to stop the coating but you have been warned.
Peter C
Last edited by peterc on Fri Jun 18, 2021 9:21 am, edited 2 times in total.
User avatar
peterc
Posts: 1549
Joined: Wed Mar 05, 2014 9:05 am
Location: Surrey

Re: Modern spark plugs

Post by peterc »

In hindsight although I had been on a couple of runs before this problem occurred it had probably been started by contaminating the plugs when warming the engine up in the garage. This was following a change of coolant hoses and trying to get rid of the trapped air. I don’t have any choke facilities so the engine would not have been deliberately over fuelled but running at a fast idle is probably not the best mixture.
So moral of the story is don’t warm the engine up without driving somewhere.
Peter C
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