[Diy_efi] OT - platinum plugs burning up wires

[Torbjörn Forsman]

I have once tried Bosch platinum plugs, on an old Skoda with breaker 
point ignition. That was no success, cold starts were difficult and 
those plugs didn't last long. So i continued using standard NGK plugs.

In my opinion, when an ignition lead goes open-circuit, this normally is 
due to bad quality of the lead itself (here in Sweden, it seems like 
nearly all resistive ignition leads sold by aftermarket companies are 
very low quality. It is often better to pick up 15-20 years old OEM 
leads from a wrecked car). Another cause is when someone is pulling the 
lead to get a stuck spark plug cap loose.

Ignition coils that are fitted on the engine and subject to much 
vibrations and heat normally doesn't get a long life. It is better to 
have the coil in a cool, calm place in the engine compartment. Maybe, 
modern coils that are potted in epoxy resin (for example, GM HEI coils) 
survive vibrations somewhat better than the old, oil- or compound filled 
ones.
For electronic ignition systems, it is extremely important to use a coil 
with the correct electrical data (mainly: resistance and inductance of 
the primary winding, and transformer ratio) for the used ignition 
module. GM HEI systems are somewhat special as they have no overvoltage 
protection in the ignition module. Instead, the coil is dimensioned so 
that the primary voltage spike can never go beyond the breakdown voltage 
of the module's power transistor. If a coil of the wrong type is fitted 
to a car with HEI, the module will fail the first time a ignition lead 
comes off or goes open-circuit!

/Torbj?rn Forsman


David Allen wrote:
>   Didn't hurt my 1991 TBI 305 with stock ign. components.  Hasn't hurt my
> mother's 1989 LeSabre with Series I 3800 and DIS ignition. On all these cars
> the ignition leads last fine.  Had one coil failure that I couldn't explain
> on the 305 but I was using a coil of unknown origin.
>   Modern graphite core wires can be fickle.  The core may be brittle; or the
> wires may be stressed or pulled during the service.  A crack opens in the
> core and as the ignition fires across this crack it burns away more and more
> of the core. Finally the wire is open-circuit.
>   However my turbo engine does not run as well with Bosch Platinums as it
> does with standard plugs.
>   Maybe I am just lucky with not ruining ignition leads?
> David
> 
> 
> ----- Original Message ----- 
> From: Bret Levandowski
> To: diy_efi at diy-efi.org
> Sent: Saturday, September 10, 2005 5:26 PM
> Subject: Re: [Diy_efi] OT - platinum plugs burning up wires
> 
> 
> Platinum plugs have a higher core resistance and require more current and
> more precise control to fire. This is not true of all platinum plugs but
> most. If the resistance in the plug or across the gap is too much, the
> current can't 'escape' through it's normal path and it has to go somewhere.
> Always the point of least resistance, whether it is the cap/rotor or plug
> wires it is going to flow somewhere. Either way, it is going to burn
> something up; possibly even your coil.
> I have experimented with different plugs and different systems and have seen
> all types of failures. From what we saw, AC Delco platinum plugs will burn
> up coils and wires quite nicely on older motors. SureFire triple platinums
> work well in just about any type of performance motor (high comp/high energy
> ignition), but not so well in older or lower compression motors. It wasn't a
> 'scientific experiment', just what we saw happen by changing plugs. So after
> much rambling..... Yes, what the tech said is true. You can burn up ignition
> components using platinum plugs in non-platinum applications. I have done it
> myself and had to have someone else tell me why. Unfortunately, you don't
> know 'til you try.
> 
> Rick McLeod <dunvegan at sbcglobal.net> wrote:
> 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
> 
> 
> 
> Click here to donate to the Hurricane Katrina relief effort.
> 
> 
> 
> _______________________________________________
> 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
>