freediver

So the car ran really great, then it didn't. We narrowed the problem down to the original, 30-year old coil. So I bought a new Bosch blue coil, made the switch and the car ran really great. Then it didn't. Unless my multimeter is bad, the new coil is bad. Does anybody have any idea what gremlin in my shark is killing my coils? Please help. There is a track day this Saturday and I'd love to run my 928 around outside track at Miller.

Mrmerlin

it would help if you would list the year of your car and the last few things that you have fixed

SeanR

Ensure the grounds for the coil are good, the wires are good, etc.

dr bob

The Bosch Blue coils are 'high output' coils designed to work with points and a condenser. The insulation isn't stout enough to put up with the ignition electronics in a 928 generally. Find the correct coil(s) and you'll probably do better.

Depending on the year of your car, you may find other causes for no-spark, Early cars have a small coax cable from a Hall pickup in the distributor. Failing/failed cable means no good spark. Of coarse the classic stuff like caps, rotors and plug iwres all need to be in good shape for the car to run OK.

Mrmerlin

depending on the year you may also have a failed resistor there are 2 of them white barrel shaped mounted near the coil on the inner fenderwell, they get hot when the car is running but both of them have to work for the coil to work

freediver

It is a 1979. A lot has been done to it, mostly removing stuff to make it lighter for the track. I guess it would be smart to get the correct coil [slapping head].

2002maniac

It's actually a '78 if that makes any difference.

Dad, what's the part number on the Bosch coil you received? Unless you asked for a blue coil specifically, they should have looked up the correct coil for a 928.

Anyone know if there are test procedures for the hall sensor, ignition box and the inline resistors? TIA we really need to get this running!

dr bob

The inline resistor stuff is easy to verify with the wiring diagrams and a volt/ohm meter. The Hall Sensor and the "green wire" coax require an oscilloscope to test effectively. The green wire is generally an age-related replacement item. If there's checking or cracking on the wire or connectors, it's a good idea to put a new one in now even if it isn't the direct cause of your current symptoms. That same o'scope will help with isolating problems in the ignition box too.

Use caution when working on ignition system components while the system is energized. Voltages on this system are significantly higher than most standard systems. A single jolt will (hopefully) drop you on your butt. Contact with even the primary system components, while the engine is running, can be fatal. The current causes muscles to contract. The ones in the hand holding the wire, and the one pumping blood through your noggin.

2002maniac

We ended up taking the car to Dave Lomas at Motorsport in SLC and he had the car running in no time. He cleaned up the contacts and replaced some old wiring and it runs great now with the old coil.

Thanks Dave!

linderpat

hmmm, not very descriptive. What old wiring was replaced. It's good to know these things for those of us who struggle with similar issues from time to time....

Maleficio

I replaced my factory coil with a Jacob's coil. Works great.

Peter Visser

I have a 1980 Euro 928s.
Browsing the net I found a thread (I think on Pelican) where the Bosch Blue coil is described as having an internal Balast Resistor. My 928 already having 2 external balast resistors this seems slightly overdone to me: could anyone explain this to me?
I have a feeling the 31 year old ignition is no longer performing as it did when the car left the factory, even after replacing plugs, leads, cap and distributor.
I'm thinking of replacing my blue Bosch coil for a Jacobs Ultra, and would be especially interested to know if Maleficio is still happy with his after having used it for +1 year?
Thanks in advance for your help!

euro trash

The coil was on my list of things to replace. I have the 'blue' coil and it looks pretty beat with one of the posts stripped. Is the blue colored coil original or was the wrong part in there ?

Doing research I see the part should be 92860250300. I do want to put the best quality coil in there, any recommendations. Was looking at these:

http://www.928motorsports.com/parts/hpcoil.php

http://www.ebay.com/itm/Porsche-928-...16d424&vxp=mtr

archer

I am running 2 blues without any issues

ALKada

Check with Rog100 aka www.928sRus.com on the best coil (and price) for your model year.