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Spark plugs...

Posted: Mon Jan 06, 2014 12:16 am
by turbo-tom
Bit of a weird one this.. its relating to my coursework the question is:

If a spark plug has the earth electrode corroded away will it still spark?

my answer id say that it wont? because it has nothing to ground out to and produce a spark etc

am i right? or am i wrong? cant seam to find an answer :/

cheers tom! :lol:

Re: Spark plugs...

Posted: Mon Jan 06, 2014 12:17 am
by Edweird
turbo-tom wrote:Bit of a weird one this.. its relating to my coursework the question is:

If a spark plug has the earth electrode corroded away will it still spark?

my answer id say that it wont? because it has nothing to ground out to and produce a spark etc

am i right? or am i wrong? cant seam to find an answer :/

cheers tom! :lol:
Sounds right to me.

Re: Spark plugs...

Posted: Mon Jan 06, 2014 12:20 am
by turbo-tom
Thats what I thought , been trawling the web and reading in books for ages for not to get an answer.

Cheers Ed :thumbup:

Re: Spark plugs...

Posted: Mon Jan 06, 2014 12:47 am
by Edweird
The only possibility is that a spark might jump from the electrode and ground through the cylinder head, but I think that's extremely unlikely due to the compression, as it is harder for electricity to pass through gasses when they are at higher pressure; hence why low pressure weather systems bring rain and storms.

Re: Spark plugs...

Posted: Mon Jan 06, 2014 12:55 am
by turbo-tom
hmm I guess that is possible but like you say very unlikely... cheers for that though!

can't wait to finish the course and get out in the fields repairing machinery :D

Re: Spark plugs...

Posted: Mon Jan 06, 2014 1:24 am
by dan_2k_uk
turbo-tom wrote:hmm I guess that is possible but like you say very unlikely... cheers for that though!

can't wait to finish the course and get out in the fields repairing machinery :D
Yeah. Those bloody land rovers. Always breaking down :thefinger:

Re: Spark plugs...

Posted: Mon Jan 06, 2014 8:11 am
by Ladaman
I'd think it would.

Surely the spark would just jump to the threaded part which is earthed to the cylinder head.

Do you have an old plug you can grind the earth electrode off, and then do an experiment?

Re: Spark plugs...

Posted: Mon Jan 06, 2014 11:10 am
by Tramp
I'd have thought it would track down the insulation and spark across to the threaded section, it only uses the cathod as it's the path of least resistance - when your plug gets wet or it gets carbon deposits on it it does this anyway. Although as the spark is recessed it won't ignite the fuel properly or at the right time, also it will be a different sort of spark as it's having to work harder, instead of a short fat blue spark it will be a longer thinner lighter coloured spark,

Re: Spark plugs...

Posted: Mon Jan 06, 2014 11:34 am
by ROBBIE
Ladaman wrote:Do you have an old plug you can grind the earth electrode off, and then do an experiment?
I would try this but first I would adjust the gap and see how the spark changes across the bigger gap

Re: Spark plugs...

Posted: Mon Jan 06, 2014 12:23 pm
by turbo-tom
Ladaman wrote:I'd think it would.
Surely the spark would just jump to the threaded part which is earthed to the cylinder head.
Do you have an old plug you can grind the earth electrode off, and then do an experiment?
That's what I was thinking first of all.. and I thought i did i was just going to test it and have a look but i couldnt find any laying around in the garage, and to see what would happen!
Tramp wrote:I'd have thought it would track down the insulation and spark across to the threaded section, it only uses the cathod as it's the path of least resistance - when your plug gets wet or it gets carbon deposits on it it does this anyway. Although as the spark is recessed it won't ignite the fuel properly or at the right time, also it will be a different sort of spark as it's having to work harder, instead of a short fat blue spark it will be a longer thinner lighter coloured spark,
hmm yeah so basically its going to explode the fuel rather then ignite it properly making the engine run hotter...


Anyway cheers Chaps! ive all taken your good info in and ill report back just out of interest when I get the assessment back! :thumbup: