Not a good start...Should I be worried?

[Martiny]

Martiny - out of interest what does that little trick do?

Ta,

Chris.

Ok, so here\'s the problem. Something prevents the plugs from firing. And the problem is very often fuel, oil, or a combination of oil and fuel residue on the spark plug.
The spark plug makes a spark because a very high voltage is sent to the  little node in the middle, and then it jumps to the body (earth or negative) of the plug - or actually to the little tab that\'s bent towards the node.
Its difficult to see, but the node is insulated from the body.
Now when there is too much fuel in the chamber, it can cover the insulation, and provides a much easier path for the current to flow to earth. And   now the current runs from the electrode, THROUGH that fuel to discharge to earth. Now there is no spark :-(

(Sometimes it\'s carbon buildup that provides this path rather than fuel)
(are you still with me!?)

Ok, now there\'s many reason why the fuel might land up on there... running too rich (car still in warm-up mode), old plugs, or low compression engine...leaking injectors.... etc.


Now , when we hold the throttle open during shut down, we are pumping air through the chamber, and this is cleaning any residual fuel off the plugs - (the   fuel will stop being injected as we switch the key off), hopefully leaving the plugs nice and dry , and give us the best chance of them firing first time the next time we start up.


Capisce?  Comprende?  Verstaan? Verstehen zie?

[Paul1982]

Good info martiny :-)

[d6277n]

Cheers matey. Useful to know

Chris.

[Brett]

Something thats not been mentioned yet - but when did you last drive it before it gave trouble starting?  If its been left awhile they do take some turning over to get going... :wave

[adib]

no see that car at rst4 i think, you will get use to things playing up one day and fine the next or is it my rex that just does this :Laugh

[Alison]

It was only left standing over night Brett, she\'s fine now, had no problems since. Must have just been in a strop! :Thumbs-up

[Teighto]

they all get like that !!

[ashc]

Now when there is too much fuel in the chamber, it can cover the insulation, and provides a much easier path for the current to flow to earth. And   now the current runs from the electrode, THROUGH that fuel to discharge to earth. Now there is no spark :-(

(Sometimes it\'s carbon buildup that provides this path rather than fuel)

i know what you mean but i thought fuel had such a high resistance no electricity went anywhere when a plug was flooded, thats why in-tank fuel pumps don\'t explode?

[Martiny]

i know what you mean but i thought fuel had such a high resistance no electricity went anywhere when a plug was flooded, thats why in-tank fuel pumps don\'t explode?

Ashc , thats an interesting topic, worthy of discussion, lets explore it.

My understanding is that petrol needs to be - a gas to ignite, and needs an open flame to ignite ( or a spark ).

Could it be that the petrol is actually INSULATING the 2 points of the plug where the spark needs to jump?

[ashc]

Ashc , thats an interesting topic, worthy of discussion, lets explore it.

My understanding is that petrol needs to be - a gas to ignite, and needs an open flame to ignite ( or a spark ).

Could it be that the petrol is actually INSULATING the 2 points of the plug where the spark needs to jump?

thats what i thought - if fuel actually conducted electricity, there would be all manner of problems! I was told this when i fitted my uprated fuel pump to my old silvia - the plugs were just immersed in fuel with the contacts exposed and i wondered if the tank was liable to go pooof....

but with the sort of voltages designed to produce a spark, maybe there is some conductance?