What happens when a coil dies.....

[Wuffer]

Had an owner have his 1991 Canadian spec 850 towed here as it was running on 6 cylinders. Car has around 230k kms (142k miles) on it. Ultimately discovered the passenger side coil had spilled its guts and self destructed as shown:


Which in turn, took out the corresponding DME:


Once both replaced, car started on all 12 but on road test, idle wouldn't drop below 1000 rpms and car was surging violently. Replaced EML and all is now better. This is not the first puking coil we have seen up here that has taken out a DME as well but the first to affect the EML. Perhaps a cautionary maintenance replacement of the 25 year old coils may prevent this expensive failure.
FWIW....

[danieldd]

Is the DME repairable at this point or are you going to have to scrap it?

[Wuffer]

DME may be repairable - depends on the degree of damage and the ability to source the correct "Darlington" transistor... and my level of ambition. 8-)
I have 8 or more known good DME's on my shelf.... so a lack of ambition will most likely prevail.

[dragon850]

Wowza !

[Wuffer]

Just as a follow-up. This was not an isolated case - it was the 5th E31 that I have had to do this diagnosis and repair on over the last couple of years. Other 4 were lower mileage J-specs and a US spec 6-speed car. I don't mind as I have plenty of coils and DME's on hand at the moment but I strongly urge you to replace your coils as a maintenance item. Using either OEM Bosch or aftermarket MSD 8207's will provide a stronger spark than your tired, worn out 20-25 year old OEM coils, improving reliability and even fuel economy and... maybe eliminate the additional cost of DME/EML replacement as well.... just my $.05 worth. My own car has MSD's.

[cdnalpina]

Sage advice. The cost of a coil is far far less than a DME or EML...

[TxGR8White]

DME may be repairable - depends on the degree of damage and the ability to source the correct "Darlington" transistor... and my level of ambition. 8-)
I have 8 or more known good DME's on my shelf.... so a lack of ambition will most likely prevail.

The Top Ten Reasons I procrastinate:
1.

[CaifanSC]

What would you gents say is a good safe interval? From my recent fuel pump conversations it was suggested fuel pumps get replaced approx every 10 yrs as maintenance items. Would you say half that for coils? 5 yrs despite mileage?

[TxGR8White]

I have replaced at 35,000 - 40,000 miles. That works out to every 18-24 months.

[G8nightman]

Just as a follow-up. This was not an isolated case - it was the 5th E31 that I have had to do this diagnosis and repair on over the last couple of years. Other 4 were lower mileage J-specs and a US spec 6-speed car. I don't mind as I have plenty of coils and DME's on hand at the moment but I strongly urge you to replace your coils as a maintenance item. Using either OEM Bosch or aftermarket MSD 8207's will provide a stronger spark than your tired, worn out 20-25 year old OEM coils, improving reliability and even fuel economy and... maybe eliminate the additional cost of DME/EML replacement as well.... just my $.05 worth. My own car has MSD's.

How did you mount the MSD unit? Any pics?

[adwebinc]

How did you mount the MSD unit? Any pics?

Interested in this as well. Would like to run the MSDs, so would love to understand how to mount.

[shogun]

I can show you similar pics, ignition coil damage
https://postimg.cc/jnSLMxYx
https://i.postimg.cc/J0bZ40Tk/Ignition-Coil-Defect.png
https://i.postimg.cc/Fzq8mPBR/Ignition-Coil-Defect1.png
But, they are >20 years old, so the quality was good. Why not change the original ignition coils every 10-15 years. I will stick to Bosch.

[garylafortuna]

These came with mounting brackets, but they should be fairly easy to fabricate.

[Sansouci]

Is heat the villain which causes the plastic housing to crack and leak?
Gary's picture of MSD's from Phoenix Motor Sport seems to have cooling fins (actual or a design element - I don't know)
--Ken

[Mikekugel]

I replaced my coils last year when I replaced the wires caps and rotors. I bought the new ring style Bosch coils from AutohauzAZ, work fine. Passed CA. Smog Very clean, and runs strong!

[TxGR8White]

Is heat the villain which causes the plastic housing to crack and leak?
Gary's picture of MSD's from Phoenix Motor Sport seems to have cooling fins (actual or a design element - I don't know)
--Ken

Those are the exact same coils - the only thing added is the expensive sticker.
You will need to make a mounting plate to be able to install them in the E31 (not difficult to do - piece f aluminum and drill a couple of holes)

[peezen]

Does anyone have a plan for the mounts? I have a guy that can make them here, but none of the threads seem to have any details on the mounting bracket

[TxGR8White]

I can put something together tonight. What format? .pdf?

[peezen]

pdf would be awesome! Thanks so much

[adwebinc]

pdf would be awesome! Thanks so much

peezen - would your guy be willing to make a couple of sets? If so, let me know how much!

- - - Updated - - -

The Top Ten Reasons I procrastinate:
1.

haha!! love it!

[peezen]

I'll ask him once I surprise him with the plans. He build metal parts for boats so he'll have no problem with this, as to whether he has time right now is another thing. I'll use my powers of persuasion though

[Moxy]

Does anyone have a preference as to the coils, Autohauz has the Bosch coils for around $50.00, if they have lasted this long assuming mine are original at 160 kms and 24 years that pretty dam good by my books

Moxy

[2001740il]

If he can not do it I have a waterjet that could knock out 20 sets in no time at all.

[Max Lumens]

Or you could simply buy the Phoenix parts; I believe I have a set here 8^)

[Ledo]

Does anyone have a plan for the mounts? I have a guy that can make them here, but none of the threads seem to have any details on the mounting bracket

I made a mounting plate some days ago, it can be very simpy cut from aluminum or any other metal. I had mine laser cut and they fit perfectly. If anyone wants the file (.dwg, .dxf, .pdf, .stl...), I wouldn't mind sharing it. If you PM me your mail, i will send it your way...