[Diy_efi] OT - platinum plugs burning up wires

David Allen davida1
Sun Sep 11 06:13:58 UTC 2005


  The internal resistance is for radio interfarence supression and for
interference on the engine electronics.  Some distributor rotors have a
resistor in them to suppress RFI at the distributor rotor-to-cap spark gap.
  Most modern plug wires are actually resistive in and of themselves. A few
have copper wire with a resistor built into the plug boot. Most are
"supresion core" wire.  Instead of a copper wire, they have a core made of a
graphite material.  A normal length plug wire may have several thousand ohms
of resistance.
  There are two main ways in which these fail.
  The graphite core can develop a small gap due to mishandling, age,
improper installation of terminals or a combination of factors.  Each time
the ignition systen fires through this wire, there is a small spark across
this gap.  The plug still fires.  Each spark vaporizes more and more of the
core creating a longer and longer gap. Eventually this gap is too much and
the spark no longer jumps the gap.  You get a misfire. This is particularly
noticable under low RPM high load conditions like climbing a gentle hill in
high gear.  Gives a "fishbite" symptom.  You can ohm out the plug wire and
it will show infinite resistance.  May have a visibly swollen or soft area.
  Second common failure is insulation breakdown.  This happens when the
insulation gets damaged by age or heat or excessive voltage due to a
disconnected spark plug or burned away graphite core.  The insulation is no
longer able to contain the voltage and a spark jumps from the side of the
ignition lead to a metal part of the engine. Once this happens it will
repeat because the inslation becomes conductive after being penetrated by a
spark, and burned or carbonized. Visible arcing, and burning of insulation
is evident.
  When a coil fires, it sends out a pulse of current.  The resulting voltage
level is a function of how much resistance there is in the circuit and how
wide and how many gaps it has to jump (plus other factors).  The less
resistance in the circuit from the coil to the plug, the less the voltage at
the coil during each spark.  If the core of the plug wire is bad, the cap
and rotor are worn out, or the plug gap is too wide- the insulation of the
ignition coil and ignition leads can be subject to much, much more voltage
than necessary.  This can lead to the second type of failure described
above.
  I would like to see a real scientific comparison of the firing voltage
difference in a given engine at the same gap- platinum versus non-platinum
plugs.  There are so many different systems out there it is impossible to
know what can happen in every situation.  Possibly on a Hyundai the ignition
system is under designed and close to its breaking point under normal
operation.  Therefore, the small increase in firing voltage from platinum
plugs is too much.
  All I know for certain is- I haven't had any damage using them in my cars
with Delco HEI and DIS ignitions.
  Just my two cents worth!
David

----- Original Message ----- 
From: hal sumption
To: diy_efi at diy-efi.org
Sent: Saturday, September 10, 2005 12:56 PM
Subject: Re: [Diy_efi] OT - platinum plugs burning up wires


Adding resistance to the circuit will lower the current and reduce the
likelihood of burning the wires.  From what I understand, the purpose of
adding resistance to the plug wires is to reduce radio interference they may
generate.
----- Original Message ----- 
From: Becker, Damon (Damon)
To: diy_efi at diy-efi.org
Sent: Friday, September 09, 2005 10:23 PM
Subject: RE: [Diy_efi] OT - platinum plugs burning up wires


Some plugs have internal resistance, others don't.  I was under the
impression this is more to avoid burning up the coil, not the wires.

-----Original Message-----
From: diy_efi-bounces at diy-efi.org [mailto:diy_efi-bounces at diy-efi.org]
On Behalf Of Geoff Harrison
Sent: Friday, September 09, 2005 9:57 PM
To: diy_efi at diy-efi.org
Subject: Fw: [Diy_efi] OT - platinum plugs burning up wires

Rick, that does sound like bunk. Your leads may have been on the way
out.
The way I see it, doesn't make much difference what the electrodes are
made of, only a small amount of current flows when the plug fires. The
gap has more influence on the current, and never enough to burn out a
lead.
My question is, did the dealer keep the plugs?

Geoff
----- Original Message -----
From: "Rick McLeod" <dunvegan at sbcglobal.net>
To: <diy_efi at diy-efi.org>
Sent: Saturday, September 10, 2005 12:59 AM
Subject: [Diy_efi] OT - platinum plugs burning up wires


Sorry for being off topic, but I know there is a lot
of knowledge in this area on this list, and this might
be of interest to discuss (remember the recent plug
discussion?)
Recently I had an issue w/ a Hyundai where the plugs
were replaced w/ platinum at a tune up. A few k-miles
down the road, the car began running poorly, and was
taken to the dealer where it was diagnosed as having
'burned up ignition wires'. The service advisor stated
that you MUST NOT use platinum plugs in these cars
since it will cause this to happen.

My question is: What is different about them that
would cause this, it sounds like 'bunk' to me, but am
looking to the vast world of knowledge on this list to
get some insight.

Thanks

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://lists.diy-efi.org/mailman/listinfo/diy_efi

_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://lists.diy-efi.org/mailman/listinfo/diy_efi


_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://lists.diy-efi.org/mailman/listinfo/diy_efi




_______________________________________________
Diy_efi mailing list
Diy_efi at diy-efi.org
http://lists.diy-efi.org/mailman/listinfo/diy_efi





More information about the Diy_efi mailing list