The only coil I can find for my '84 928S is a MotoRad as sold by Pelican and others. I believe the manual specifies a coil resistance of 0.4 to 0.7 ohms / 5k to 8.7k ohms but the MotoRad is 1.4 / 8k. Any problem with running this? That spec sounds like a standard coil for a whole bunch of cars, not anything special for a 928 or anything.

 

call Mark at 928 INTL and get a used coil,
they are about the best parts you can get.
NOTE using the aftermarket NON Bosch electrical parts,
could possibly damage the rest of your system or cause other failures.

 

Thanks, sound advice. I'm just concerned that any used coil I buy will also be 40+ years old with an unknown history and remaining lifespan. At some point the Bosch coils will be extinct so I wonder if there are any good alternatives? The ones I can find have a higher secondary resistance and therefore higher spark, but I wonder if that will matter so long as the primary is correct.

 

The significance of what I suggested is that the 40 YO Bosch coils still work as they should,
as they were made with better materials, and seldom fail.

IOW its usually something else thats causing the disruption to the proper operation.

Since your car has a green wire this is the first place I would look .

NOTE Only use the Bosch green wire,
the less expensive URO brand has been demonstrated to have been poorly MFGd,
and will usually cause the engine to stop running

 

Thanks, I did confirm it was the coil. Normally they seem to fail slowly, causing running issues that worsen when hot, but this one was perfect and then failed quite suddenly so it took me a bit to figure out that was the cause. I did check the green wire and it was working fine, but the connector fell apart in my hand so I got a new OEM wire.

 

New question, how do I identify the Bosch versus URO? I bought a wire from Pelican a while back


but it only says Porsche OEM, not Bosch.

 

the way to ID it as Bosch will be that it slides easily into the distributor and the lock plate does not have to be forced to hold the connector into the body of the dizzy.
NOTE you will have to carefully trim off the black spacer on the dizzy connector

 

No way to tell without removing it from the packaging and installing it?

 

The MSD Ignition Coil - Blaster Series - High Vibration - Black are probably the best new coils made. These are made for offroad racing and the heat of off road racing. They are not cheap Chinese stuff and on my car makes just a bit more voltage than the Bosch oem ones.

 

I was looking at those. The primary is correct, and although the secondary is below spec they still produce more voltage. Seems like a decent replacement.