When to replace spark plugs?

[Aviator5]

Re: When to replace spark plugs?

There is no huge magnetic field, and no huge current in secondary, in fact there is no huge current in primary either, about 12A max. Overall energy dissipation is around 100 Watts only. It is a number of windings that produces high voltage.

 

[bruceb58]

Re: When to replace spark plugs?

I don't think you understand how a coil works in an ignition system.

Read this.

http://auto.howstuffworks.com/ignition-system3.htm

 

[Aviator5]

Re: When to replace spark plugs?

Yes, that what it says "High voltage current", not "High current". There is noithing but voltage is "high", or "huge" there.

 

[bruceb58]

Re: When to replace spark plugs?

Yes, that what is says "High voltage current", not "High current". There is noithing but voltage is "high", or "huge" there.

LOL...you crack me up. OK..if you get past those semantics can you see about the field collapsing and that the field induced on the secondary coils causes the high voltage?

 

[Aviator5]

Re: When to replace spark plugs?

if there was a high current there, then you would have an arc welder, not the ignition coil.

 

[JustJason]

Re: When to replace spark plugs?

There is no huge magnetic field,

Huh? Thats how coils work. There's basically 2 different types. Riseing field and collapsing fields coils. Both work by generating not high voltage, but a high magnetic field and that field gets induced to a secondary set of windings, in that secondary is where the magnetic field turns into high voltage. I'm not positive if I worded that correctly, but that's how it works.

It is a number of windings that produces high voltage

Sorta agree. But it's really more the number of windings we twist around an iron bar the stronger of a magnetic field we are making, think electromagnet. It's how we control that magnetic field, or what we do with it, is how we can get such high voltage for brief moments. Think about how big a coil would have to be if we were trying to make a sustainable 30+ thousand volts, it would be enormous.

 

[Aviator5]

Re: When to replace spark plugs?

Huh? Thats how coils work. There's basically 2 different types. Riseing field and collapsing fields coils. Both work by generating not high voltage, but a high magnetic field and that field gets induced to a secondary set of windings, in that secondary is where the magnetic field turns into high voltage. I'm not positive if I worded that correctly, but that's how it works.



Sorta agree. But it's really more the number of windings we twist around an iron bar the stronger of a magnetic field we are making, think electromagnet. It's how we control that magnetic field, or what we do with it, is how we can get such high voltage for brief moments. Think about how big a could would have to be if we were trying to make a sustainable 30+ thousand volts, it would be enormous.

Everything depends on current, in case of ignition coil, the current in a secondary is milliamps, so to produce sustainable 30+ kv is not that big of a deal. As I said it dissipates about 100 watts only. So there is nothing huge there but voltage.

 

[bruceb58]

Re: When to replace spark plugs?

I don't even know where Jason is going with this...not sure he does either.

Aviator...does it make sense what I said about the internal insulation break down?

 

[Aviator5]

Re: When to replace spark plugs?

I have to confess, that my staitment that condition of the spark plug won't affect the voltage was incorrect. The bigger the gap, the higher voltage is, but the current goes lower. In case of the open circuit it will raise up to 30-40 kv. but current is 0.

 

[Aviator5]

Re: When to replace spark plugs?

I don't even know where Jason is going with this...not sure he does either.

Aviator...does it make sense what I said about the internal insulation break down?

Yes it does, but I don't think they would design the coil that can't withstand an open circuit voltage.

 

[bruceb58]

Re: When to replace spark plugs?

I think that is all we disagree on. My understanding is that this is what causes the coils to fail for that scenario.

 

[Aviator5]

Re: When to replace spark plugs?

Maybe, but I would expect it to happen after a number of hours running. But normally the operator would realize that motor is misfiring and take an action to fix it.

 

[bruceb58]

Re: When to replace spark plugs?

Maybe, but I would expect it to happen after a number of hours running. But normally the operator would realize that motor is misfiring and take an action to fix it.

That could easily happen..in fact, could be days. It is definitely going to be a cumulative affect over a long period of operation

 

[Aviator5]

Re: When to replace spark plugs?

I had my 2000 Malibu running on sparkplugs with no ground electrode left at all, it was completely gone after 200000 miles without spark plug change. Car wouldn't start after all, but coils were fine. At the same time ignition coil failed on my 93 Safari, with perfectly good sparkplugs.

 

[JustJason]

Re: When to replace spark plugs?

boat engine coils work harder than automotive counterparts.

And when i was talking about current, I was talking about current going into the coil, not comming out of it.

 

[Aviator5]

Re: When to replace spark plugs?

boat engine coils work harder than automotive counterparts.

And when i was talking about current, I was talking about current going into the coil, not comming out of it.

Current going into a coil is not that huge either.

But back to subject. I do inspect my sparkplugs in the beginning of season (all 12 of them) and who knows how many times during a season, at least 1-2plugs on each engine every month, the ones that easy to reach. Spark plug can tell you a lot about your engine.

 

[bruceb58]

Re: When to replace spark plugs?

I had my 2000 Malibu running on sparkplugs with no ground electrode left at all, it was completely gone after 200000 miles without spark plug change. Car wouldn't start after all, but coils were fine. At the same time ignition coil failed on my 93 Safari, with perfectly good sparkplugs.

Depends on where the spark is arcing. If the wires were also degraded, you could have had an arcing to ground at another point along their length. Or the arcing could occur external to the coil...even at its tower to ground. It all depends on which path is the least resistive.

 

[Aviator5]

Re: When to replace spark plugs?

Depends on where the spark is arcing. If the wires were also degraded, you could have had an arcing to ground at another point along their length. Or the arcing could occur external to the coil...even at its tower to ground. It all depends on which path is the least resistive.

Well, that would cause engine to misfire. I'm lasy and cheap when it comes to car maintenance ( does not apply to my boat!!!), but I wouldn't drive 6 cyl car on 5.