mazing3

yep- They are 2 cylinder looking things about the size of a roll pennies.

In front of the engine, about a foot away from the coil on the left side wall. Look about half way down, mounted with just 1- 10mm bolt. Take the intake tube off on that side of course too.

They are pretty obvious to see when you look over there.

Good luck.

Robbie

crushingday

Thank you sir! Is it really supposed to be .4 and .6 ohms or did you mean 4 and 6 ohms

linderpat

My goodness, I never thought about those things one way or the other, and had no idea what they were for. Now there is one more thing to think about with respect to performance issues. I'll be going through the WSM to find out more.

9two8

The two ballast's located just in front of the PS reservoir bolted to inner fender.

http://members.rennlist.com/sharkski...istorCheck.jpg

hacker-pschorr

Years ago when my 81 still had the stock ignition I was having issues with a mis-fire above 5k RPM under boost (about 17 psi).

Long story short, at some point I tested those resistors and they were out of spec so I bypassed them, went for a drive and nothing changed. Unfortunately I don't have notes on how far out of spec they were to compare to this situation. Bottom line though, for "regular" driving having them out of whack didn't make any starting or running difference with my 81.

I also thought they were only in play during curtain times (like cranking) and not in use all the time. Need to take a close look at the wiring diagram to refresh my memory.

Either way, they are easy enough to bypass and if the problem doesn't instantly go away that is not the problem.

As suggested before, if the age of the green wire is not know - start there - it's the life blood of the ignition (and supplies a signal to the fuel brain on 80-84 US cars) and cannot be "bench tested" to determine if it's any good. Owning an 84 or older 928 means it's a good idea to have a "known good" green wire on hand at all times to troubleshoot with.

linderpat

What is their purpose? Are they like a gall bladder or appendix, something good to have but not needed to live a fairly normal life?

Also, the OP said he has swapped in 3 green wires, so that probably is not his issue.

hacker-pschorr

There are two, one I'm positive is used when cranking, I don't recall what the other is for or when it's in play. I'll check the WSM tonight unless someone gets to it sooner.

I saw that, just an FYI for anyone playing along at home.

On that note, I've had a couple ignition brains fail (box in the inside passenger side fender, below where the green wire connects). Each time it caused odd / random / intermittent issues.



Have we positively, 100%, absolutely ruled out a CIS issue? These ignition systems are stupid simple, CIS on the other hand....without the proper tools you are shooting in the dark guessing where the problem could be.

James Bailey

the coil never sees 12 volts, when cranking only one resistor is used (feed from starter motor circuit), normal running power passes through BOTH. That supplies a hotter spark for starting then an even lower voltage for normal running. That also can cause the car to start then die if the second resistor in series has failed.... Resistors get hot that can cause an open circuit and intermittent failures too. The Porsche style resistors were NLA many years ago but Mercedes also used similar units rectangular not round but function the same....Again the coil is not supposed to run on 12 volts an CAN overheat and burst spewing tar like stuff all over the inner fender.

mazing3

UPDATE--- it's not fixed.

Thought it was but bypassing the ballast did make it fire up. For about 30 seconds of rough idle, then the rpms shot up to about 2,800 and it died. That was still better than what it was doing before but I'm not quite sure I understand why it was even running. Eventually even with them jumped, we are back to the standard (turns over-VROOM-dies) I'm guessing that is just the CSV fuel igniting.

Either spark or fuel is cutting off here and I'm not sure which it is yet. I'm stuck at home with this thing and my timing light, Elec flow diagrams and my other tools at the shop I share space at.

Going to try a few more things and report later. Thanks

Robbie
78 5spd

jpitman2

I would be VERY surprised if a std DVM could give you an accurate reading of a resistor rated at less than 5 ohms, much less one rated at less than 1 ohm! If suspect try taking them to an Auto Elec, or buy new ones. Corrosion or poor contact is all I can see changing their apparent values.

jp 83 Euro S AT 56k

mazing3

I d

mazing3

Mm

hacker-pschorr

Have you done any testing of the fuel system?

These ignition systems are stupid simple. Pull a spark plug wire, connect a spark plug and crank the engine over. See spark? It's working
Before doing this I pull the fuel pump relay and start the car to burn off any fuel in the lines.


Read this:

https://rennlist.com/forums/928-foru...-pressure.html

A lot of threads on this topic, that is just the first one I found.

mazing3

The last time I had the gauge rig on to see all my pressures was in December. However, I have replaced a number of things since then and never taken another look. There's almost no way everything is still in spec. Thanks for the advice!

Good call on the burning off the fuel in the lines. I had never heard of that. Makes sense.

Robbie
78 5spd

jpitman2

I got an email about a post from the OP saying 'My MM does' re my comment on DVM accuracy, but I cant see it here? Anyway, I did say a 'std DVM', so tell us the make and model and cost of your MM please, so we know .

jp 83 Euro S AT 56k