What happens when a coil dies.....

[execmalibu]

Are the coils in the later M73 cars more reliable???

[shogun]

Same on M70 and S70 = 2 ignition coils.
E31 850Ci Coupe, M70, AUTO (EG23) : RING-TYPE IGNITION COIL
E31 850Ci Coupe, M70, MANUAL (EG13) : RING-TYPE IGNITION COIL
E31 850CSi Coupe, S70, MANUAL (EG93)

The M73 has 12 ignition coils http://www.realoem.com/bmw/showparts...g=05&lang=enUS

And what do you mean by more reliable. Is 20 years not enough?

[Joelchester]

I take it this does not apply to coilpacks...(840ci) ? Cheers,Joel.

[adwebinc]

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

Bill - how much for the Phoenix coils with mounting brackets? Sounds like the easier way to go. Feel free to PM me.

[Wuffer]

Thanks Erich - good to know I am not the only one seeing the sky falling. 8-)

[fursideup]

I think you mean the E38 740 with the m60 and m62 engine. My E38 M73 - 750 cars all have a single coil per bank. The RealOem website is showing the wrong info.

[execmalibu]

All three of my M73 850ci definitely have two coils! (see attached photo). They look different then the M70 coils and might be the "Ring Coils" I have read about. I think they are upgraded from the M70 coils?

As far as reliable for the record I have the ORIGINAL Bosch coils in my 1957 Porsche Speedster, In my 1973 Porsche 911S and in my 1971 MB 280SL. The Original small black Bosch Coils for 911s are very desirable and expensive. The Bosch coil in my 560SL has been working perfectly for almost 200,000 miles.

Every car on the planet had coils until the 1990s. Not to say never but a failed coil in old cars especially BOSCH coils in German cars was very unusual... If those Bosch Coils lasted 40-60 years and are STILL going strong then I would say that 20 years on the M70 coils even on a car with very low miles is not that reliable for a coil... In reality the fact that it is recommended that you should replace them regularly to protect your EML kinda sucks... Luckily they are cheap and there are improved alternatives..


The M70 coils are poorly engineered because the MSD coils are the same physical size, they do not fail and you can run any type spark plug. That has to say volumes about the Bosch coils!...

[Joe850V12]

I just recieved 2 msd coils, mission creep, now I need make brackets. Hopefully this kill the miss. It feels like one or cylinders are not fireing

I have done the caps and rotors, will do spark plugs next then the coils, if still missing, then wires. Maybe I should just have had the indy put a scope on it and tell me what is really wrong haha!

[peezen]

Quick questions as I also have the MSD's on the way; is it the coil pack that now allows us to use any spark plugs we want, or do the wires need to be replaced as well? Also, I bought a rare set of stock plugs for our cars from Wuffer, is there any benefit to using platnums now that I'll have MDS coils?

[Fatandre]

I have the MSD laying on the shelf.
DOnt you need new cables for the MSD coils so they fit properly?

[adwebinc]

I have the MSD laying on the shelf.
DOnt you need new cables for the MSD coils so they fit properly?

You can do a conversion on the current wire (replacing the coil end boot). Max Lumens (Bill) sells a new king wire that I believe would be compatible with the MSD coils (someone correct me if I'm wrong).

[Fatandre]

5What if you have magnecore cables?

[8forever]

All -BMW Ignition coils are approx. 10,000volts. Better Alternative is the upgrade from Phoenix MotorSport speak withGerry Speechley. they Provide two MSD 8207 coils 40,000 volts and thetriangle brackets nuts and bolts for total installation. Its cheaper to buy the coils and then make thebracket, however the price to make the unit in time and material possibly worthbuying from Gerry. He also supplies aspecific coil wire for this upgrade.
http:// www. phoenixmotorsport.co.uk

Performance is excellent. Instant starting, no long cranking. Nomissing at idle, runs much smoother. My understanding is the originalsparkplugs are 0 resistance and the wires provided from BMW are solidwire. This works well with the original coils however 0-Resistance plugsare not available only resistance types yielding missing, etc. At25 years plus the coils are worn. therefore I installed, two years ago andam completely impressed enough to write this review. I did speakwith MSD as I sandblasted and painted the Red coils Black, technical supportwas agreeable and saw no problems with concept. In practice works greatwith no issues. The only thing I miss is the long great startinggear drive motor cranking, was like starting up a P-51. Ah, now itstouch the key and it goes. -8forever
coil photo-2.pdf
coil -photo-1.pdf

[shogun]

Originally Posted by whiteghost1
On a stock m70, I doubt there is any benefit to upgrading plugs other than an increased service interval. These older motors seem to respond best to the simple cheap copper plugs, even if you've upgraded the coils. I personally would stick with the stock "higher resistance" factory replacements, and replace as specified.
With the Blaster SS Coils I feel that this is like an engine oil thread, and it becomes personal preference at this point.

Originally Posted by Wokke
+1.
I changed to the MSD coils out of curiosity. No change whatsoever. An engine with 8.8:1 compression doesn't need any high performance ignition system.
All those "upgrades" on the M70 ignition side are a waste of money IMO. If it would make a difference I'd have it in my portfolio.
Shogun's recommendation is also mine

http://www.bimmerforums.com/forum/sh...=racing+engine

[m6bigdog]

+1 to both OP's
An OE ignition system either works correctly or the engine will display misfires or pings due to failed ignitions system components.
A correctly functioning ignition OE system will perform as well as any possible effort to upgrade the ignition system with aftermarket parts.
The down side of a high current un-suppressed spark ignition is it generates loads of RF interference that can get into the audio system. The RF interference suppression is a major feature of the OE M70 & M73 ignition system, hence the resistor plugs, resistor plug socket and distributor connector.

As for the Coil and DME Failure issue:
IMHO, this isn't even close to being a chicken or egg analysis, i.e., did the coil or DME fail first?
I contend if the coil and DME are destroyed then the DME is what failed first; analysis from individual that has worked in the component level electronics world for over 50 yrs.

Reasoning: the coil is "pulse transformer" designed to be pulsed by the DME on the .5 ohm primary winding to generate the desired spark on the secondary side. A correctly functioning modern DME coil drive circuit is both pulse width and current limiting to protect the coil through the full range of operation. The coil design cannot tolerate a constant current and therefore will fail in short order if it is subjected to such a direct current condition. Back in the days of the distributor with points the coil had a ballast resistor to prevent coil damage due to an extended ignition on DC condition with the points-closed situation.

Therefore, should the DME output darlington transistor fail (short is the normal semiconductor failure) that would applying a DC voltage across the .5 ohm primary winding without current limiting which will just bake the coil until the dielectric expands and ruptures the case. I anticipate if you have the meter you can verify the primary winding is still .5 ohms and the coil will still generate a spark when pulsed despite the obvious case failure.

IMHO, you can replace the coils as a PM, however should the darlington fail in your aging DME the shorted darlington will still destroy the new coil just like it does the old ones.
I'm not saying not to replace the old coils, as I believe ignition system PM is necessary and should also include other components such as the complete ignition wire set, distributor cap
& rotor, etc, as needed (you make the call on mileage vs years) to have a more reliable ignition system.
FWIW, the E31 is maturing and replacing everything is not feasible and failures are inevitable despite the most aggressive PM schedule.
The best any of us can do is make the repairs cost effective (DIY) and perform enough PM to prevent the most common failures for the years vs mileage on your E31.

Old car are never cheap but they can be cool if they are well maintained.
Otherwise they will just be unreliable and an infinite source of aggravation.

[Timm]

The OEM HT voltages are actually 30,000 Volts as designed!

[adwebinc]

I have a set of the blasters with properly soldered coil wires. Put them on, no difference. Replaced all other ignition components, miss gone and idle smooth.

PS. I have a pair of VERY lightly used blaster coils with wires for sale if anyone wants to give them a shot. LOL.


Sent from my iPad using Tapatalk

[m6bigdog]

Are the coils in the later M73 cars more reliable???

The M73 uses the same coil as the M60 & M62, V8's and I anticipate all the OE coils are very reliable given the relatively low failure rate for the actual miles driven.
On my E38 with a M62, I had a plug socket that failed @ 170k miles and the coil remained functional. On the M62 the coils are embedded in the valve cover trim so they are constantly running at a very hot engine temperature.
I would not include a ruptured coil case as a coil reliability failure unless the DME remains operational because as I posted, I anticipate it is the DME output device failure that destroys the coil and not the coil that destroys the DME output device.

[shogun]

Hella general info: The amount of high voltage induced depends on the speed of change in the magnetic field, the number of windings on the secondary coil, and the strength of the magnetic field. The opening induction voltage of the primary winding is between 300 and 400 V. The high voltage on the secondary coil can be up to 40 kV, depending on the ignition coil. Car-electronics-and-electrics/Check-Ignition-coil https://www.hella.com/techworld/uk/T...ion-coil-2886/

Bosch website info: The air-fuel mixture in the combustion chamber is ignited by a spark. For the spark plug to generate the spark, it needs an ignition voltage of around 30,000 volts. The ignition coil generates this voltage from the 12-volt voltage of the vehicle electrical system and delivers it to the spark plug at the ignition point. The ignition coil functions like a transformer. It uses two coils, one inside the other, to transform the electrical energy from the vehicle battery into high voltage, stores it briefly and then delivers it to the spark plug as a high-voltage surge. Ignition energy 50-90 mJ , Secondary voltage > 30 kV


The Bentley manual mentions for testing the ignition coils on page 120-7 for the E32 M30 and M70 engine:

ignition system resistance specifications
components..............................terminals. .................................resistance
coil primary
coil code 2051118335..........1 (-) and 15 (+)................................0.50 ohm
coil code 20510171101........1 (-) and 15 (+)................................0.37 ohm

coil secondary
coil code 2051118335..........15 (+) and 4 (ctr)................................6.0 k ohm
coil code 20510171101........15 (+) and 4 (ctr)................................9.0 k ohm

spark plug ends 5.0 +/- 10% kohm
shielded plugs 1.0 +/- 20% kohm
spark plug wires 0 ohm approx.
rotor 1.1 +/- 1-% k ohm

The E32 BMW workshop manual shows for checking M30/M70 ignition coil this info on page 12-13/1. measure resistance of primary coil with multimeter term 1/15 = 0.5 ohm +/- 10% and of secondary coil term. 15/4 = 6 kohm +/- 10%
connect BMW service tester to diagnostic plug, perform test step 09 of engine test. observe the oscilograph, - ignition voltage of 6 to 14 kV. Check ignition voltage deviation .....<3 kV.

Just out of curiosity, how do you test your ignition coils besides ohm check and visual check? I have a inline spark tester, that shows me some results, at least visual.

[msoft]

Yesterday as I was analysing the Lambda regulation via INPA, I decided to to remove the cover on the RH side compartment E-box to check if the Lambda sensor heating relay was working. Suddenly during engine idle, I saw smoke from one of the DMEs. I was chocked! When I opened the DME, a transistor was seriously burned.

dme_burned_component.jpg

I assume this is due to a bad coil and I picked this up in another thread:

From Hella Techworld:
INTERNAL SHORT CIRCUITS : Overheating of the coil caused by the aging process, a faulty ignition module, or a faulty output stage in the electronic control unit.
FAULT IN THE VOLTAGE SUPPLY: The coil charging time increases on account of the voltage supply being too low, this can lead to premature wear or overload on the ignition control unit or the output stages in the electronic control unit. This can be caused by faulty wiring or a weak battery.
MECHANICAL DAMAGE: Damage to the ignition cables caused by marten bites. A faulty valve cover gasket and resulting engine oil leaks can damage the insulation of plug slot coils. Both of these causes lead to sparkover, and thus premature wear.
CONTACT FAULT :Contact resistance in the wiring due to humidity penetrating in the primary and secondary area, also frequently caused by engine washing or the use of grit in winter.

Possibly, battery voltage had dropped some due to the INPA tests and in combination with an aged coil, I guess it close to just short-circuited. The funny thing is that the engine kept running without any signs of this failure.

I read somewhere that the transistor is a "TIP162 TO-3P NPN darlington 380V 10A" and I plan to replace it together with two new ignition coils. I really hope I won't see any more smoke after that :-)

[shogun]

@ msoft: could you repair the DME, if so, which transistor did you use?
BTW, the original BMW ignition coils have flwg data:
The BMW workshop manual shows for checking M30/M70 ignition coil this info on page 12-13/1. measure resistance of primary coil with multimeter term 1/15 = 0.5 ohm +/- 10% and of secondary coil term. 15/4 = 6 kohm +/- 10%
connect BMW service tester to diagnostic plug, perform test step 09 of engine test. observe the oscilograph, - ignition voltage of 6 to 14 kV. Check ignition voltage deviation .....<3 kV.

Here is the original fault finding file from BMW in German language for DME 1.1, same applies for 1.3 = all M30 engines and M20 https://web.archive.org/web/20141031...DME11-735i.pdf
The M30 has the same ignition coil as the M70 for cylinder 1-6.
page 1210-OB-06: Zuendspule = ignition coil:
primary: 0.5 +/- 0.1 ohm respect. 0.4 +/- 0.1 ohm (B35)
secondary: 6.0 +/- 1.0 kohm respect. 9.0 +/- 1.5 kohm (B35)

page 1210-OB-05 Zuendspule = ignition coil testing
bei betriebswarmen Motor betraegt die Zuendspannung 10 +/- 2 kV. = at operating temp engine 10 +/- 2 kV. Die maximale Differenz der einzelnen Zylinder soll 3 kV nicht ueberschreiten = the max. difference between the cylinders should not exceed 3 kV

[shogun]

On the E32 forum a member changed >25 years olf ignition coils on his M70 and he explained what improved, quote: @Shogun, I just guessed. I unplugged one side, and the engine ran even worse. When I unplugged the defective side, the engine ran much smoother, albeit on 6 cylinders. So the ignition coil wasn't completely dead, but most likely providing weak spark or sporadic spark, thus making the engine run poorly. unquote