Good morning to all,
This past weekend while traveling, I had an ignition coil fail while simultaneously encountering an ECU fire on dme #1. Upon closer inspection it appears as though it started at one of the pins on the dme as the connector is melted at one point. The attached pictures tell the story. The coil only had about 3000 miles on it.
Perhaps someone here can chime in on what would cause this to happen on an otherwise perfectly running vehicle?
Attachment 644198Attachment 644199Attachment 644200Attachment 644201Attachment 644202
Wow only 3k miles, That's scary! Sorry to see this, The coils are a very important maintenance item, Should be replaced every 40 to 75K in my opinion, They are the culprit of your DME damage usually, That yellow snot looking crap usually poors out of them. FWIW i would try MSD coils next round, I haven't seen them fail yet, I'm going on 4 years with them now.
Just be sure not to test another DME with that bad coil, It will take out as many as you put over there.
It is difficult to say what happened first - either the coil failed and caused the FET output stage of the DME to self-destruct; or, the FET failed short-circuit (they do that) and burned the coil out.
Whatever it was, both the coil and the DME needs to be replaced. When this happened on my 740i (which has 8 x output FET's and 8 x coils) I replaced the FET and the coil and all was good again - but your FET failure does seem to have caused quite a lot of damage to the DME:
https://www.meeknet.co.uk/E32/ECU/Index.htm
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I installed the MSD Blaster coils 8207 a couple of months ago along with NGK platinum plugs and car is running fine. The coil wire on the car will need a 'clamp' style connector to fit the MSD primary terminal. You will need to make some adapter plates to mount the coils to OEM mounts. I owe credit to someone on here because I used his design for the adapter plates but I dont remember who it was that came up with the design.
Attachment 644225
Attachment 644226
Attachment 644227
Can you make more for $$
If I had some sophisticated equipment I would but I just used a scroll saw, files, and sander so it takes too much time making them by hand. If anyone uses the drawings in photo be sure to measure the mounting holes so that you can enlarge the drawings to the correct size.
I did pretty much the same but yours look a tad better, Good job!
Thanks! I printed up the drawings and then used some spray adhesive on paper to stick drawings to 3/16" alum plate. That was the easiest way for me to transfer the pattern to material without going to extra work. Just wish I could remember who came up with the original design on here.
copied from the E31 forum, this is not the first case I have read about, just a reminder that the ignition coils do not last forever. However, in my opinion the original Bosch ignition coils for the M70 are fine, no need to replace them with MSD Blaster coils
https://www.bimmerforums.com/forum/s...&highlight=MSD
Last edited by shogun; 01-22-2019 at 03:09 AM.
Shogun tricks and tips for the E32 series are HERE!
Here is a billet MSD coil mount but I called them when I needed mounts and the spacing on theirs was not close enough to fit the OEM bracket. And, there's not enough material to slot the holes to make them work.
https://shop.speedunlimited.com/p-10...8207-coil.aspx
^^^After reading through that thread and conducting a bit of extra research, it seems reasonable to conclude that the dme transistor is what actually killed my 3K mile coil. Is there any preventative maintenance that can be performed to mitigate the potential for this happen again in the future, i.e. DME rebuild service with newer components?
In the world of cheaper engineering vehicles, the common issue for failing ignition or ignition related parts is a poor ground, or poor conductivity resulting in fluctuating currents.
On the jeep I have added extra ground loops because of the electrical design dating from the 60's. The 740 design is a lot better, as the battery cables are less likely to corrode internally which is very common for vehicle with the battery inside the engine bay, even the honda battery wires need to be freshen up.
I would suspect water infiltration
good info from Hella with pics in the link below
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.
3 SYMPTOMS OF A FAULTY IGNITION COIL: SYMPTOMS
•Engine does not start
•Vehicle misfires
•Poor acceleration or loss of power
•Engine control unit switches to limp-home mode
•Engine warning lamp lights up
•Fault code is stored
4 MEASURING THE IGNITION COIL: BASIC PRINCIPLES
Dismantled state
There are different ways of checking the ignition coil:
Testing the resistance values of the coils using the ohmmeter.
Depending on the ignition system and ignition coil design, the following reference values apply: (observe the manufacturer's specifications)
Cylinder ignition coil (transistor ignition system)
Primary: 0.5 Ω–2.0 Ω/Secondary: 8.0 kΩ–19.0 kΩ
Cylinder ignition coil (electronic ignition system with map-controlled ignition)
Primary: 0.5 Ω–2.0 Ω/Secondary: 8.0 kΩ–19.0 kΩ
Single-spark or dual-spark ignition coil (fully electronic ignition system)
Primary: 0.3 Ω–1.0 Ω/Secondary: 8.0 kΩ–15.0 kΩ
PRACTICAL TIP
Note:
If a high-voltage diode is built into an ignition coil to suppress sparks, it is not possible to measure the resistance of the secondary coil.
In this case, the following method is helpful:
Connect a voltmeter in series between the secondary winding of the ignition coil and a battery. If the battery is connected in the diode's conducting direction, the voltmeter must display a voltage. After reversing the polarity of the connections in the blocking direction of the diode, no voltage must be displayed. If no voltage is indicated in either direction, it can be assumed that there is an interruption in the secondary circuit. If a voltage is indicated in both directions, the high-voltage diode is faulty
Installed state
The following checks can be used:
Visual inspection
•Check the ignition coil for mechanical damage
•Check the housing for hairline cracks and sealant leaks.
•Check the electrical wiring and plug connections for damage and oxidation.
Check the electrics using a multimeter or oscilloscope
•Check the voltage supply to the ignition coil
•Check the triggering signal from the ignition distributor, ignition control unit, or engine control unit
•Illustration of the high-voltage curve using an oscilloscope or ignition oscilloscope
Testing with the diagnostic unit
•Read out the fault memory of the ignition system or engine control
•Read out parameters
During all testing work on the ignition system, please note that faults established during tests with the oscilloscope are not necessarily faults caused by the electronic system; they can also be caused by a mechanical problem in the engine. This may be the case, for example, if compression is too low in one cylinder, which means the oscilloscope shows the ignition voltage for this cylinder to be lower than that of the other cylinders.
NOTE
Although "diagnosable engine management systems" are installed in today's vehicles, a multimeter or oscilloscope must be used when checking ignition systems. In order to interpret the displayed measuring results and figures correctly, additional employee training is usually required. One important pre-requisite for successful diagnostics is a careful visual inspection at the beginning of the troubleshooting process.
https://www.hella.com/techworld/us/T...ion-coil-2886/
Shogun tricks and tips for the E32 series are HERE!
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.
Attachment 672050
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 :-)
Yikes, that's scary. I just ordered a new Bosch ignition coil today, the one in my car is 28 years old.
90,700 miles 1992 BMW 735iL Azure Blue Metallic with Silver Grey leather interior ‣My car ‣My YouTube channel
For preventative maintenance, in addition to replacing coils, should we be replacing transistors or any other components on the DME PCBs?
probably to difficult for the average and/or even more experienced DIYer, but there are companies which repair ECUs, as I have plenty of stock of DMEs + EML controls for 750, I will not try to repair.
Shogun tricks and tips for the E32 series are HERE!
Hm, ok. Still would be a really big headache if the DME connector gets melted. Wouldn't be fun splicing in a new one. What if this happened if you were somewhere remote? And concerning that original poster had only a few k miles on a new Bosch coil....
So after reading the info from Hella above, just to be clear -- steps for prevention:
1. Ensure battery isn't weak, proper alternator charging. Grease battery terminals with electrically conductive grease.
2. Inspect spark plug boots, ensure cleanliness. Prevent oil/water contamination by greasing with dielectric grease. Check for any physical damage
3. Don't pressure wash engine -- we should all know this -- protect connectors from humidity by greasing with dielectric grease
Last edited by paulmer; 05-27-2020 at 10:58 PM.
Fires under rear seat happen more often, there you have to take care, the rear window heater fuse melts/get's fire https://www.bimmerforums.com/forum/s...fire+rear+seat
Johan did a fuse box rebuild http://bmwe32.masscom.net/johan/fuse...ox_restore.htm
I use on a regular basis contact cleaner and enhancer, BMW even has a TI for that
Stabilant 22A Electrical Contact Enhancer Model: All BMW
Complaint: Connectors which carry low current are more likely to form deposits which affect the resistance of the circuit through the plug connector. Depending upon the particular circuit these deposits can cause malfunctions and consequently activate warning lamps and check control indicators.
Remedy: Part replacement can temporarily stop the problem.
If the connector is the problem then without disconnecting the connector measure the resistance of the circuit running through the connector to make sure the connector has a high resistance. A good resistor will have close to 0 ohms resistance.
Visually examine the male and female terminals in the connector housing by removing them. Look at the integrity of the wire crimps, and in some male terminals the integrity of the weld of the male pin to the terminal. Then reinstall.
With a zero residue electrical contact cleaner liberally spray the male and female connectors, and allow the air to dry. Apply Stabilant 22A to both male and female terminals so they are saturated, and reconnect the connectors while they are still wet. When the Stabilant 22A dries it will leave a thin coating of polymer film which is conductive between mating surfaces, and is non-conductive between adjacent pins. It can also prevent the formation of more harmful deposits.
Last edited by shogun; 05-28-2020 at 12:45 AM.
Shogun tricks and tips for the E32 series are HERE!
I've been too lazy in my new 750 ownership so far to remove the rear seat, but after reading all of that -- well, I guess I have to now lol
When i burned my DME the other day (post above) I used INPA to look at the analog values from exhaust system as I sometimes get the INPA code 201 "Lambda integrator Regulator stop". In INPA you can also activate things like the fuel valves, lambda heater relay and purge valves and I played with this prior to starting the car. I wonder if any of this can be related to the transistor meltdown? Shouldn't be possible but a strange coincidence indeed. I could hear the purge valves clicking but could not hear that the lambda heater relay got activated.
Very important to check fuse under rear seat. I caught mine just in time, the fuse was starting to burn/melt. PO never bothered with it. I disconnected the battery, pulled all fuses and relays and sprayed the fuse box thoroughly with QD electronic contact cleaner then replaced all fuses with new. This applies to all E32s! I'm appalled by how many fire hazards exist on the E32 platform. Shocking that BMW never issued a recall, its a very dangerous car to drive apparently. I lost one to electrical fire already, every day I fear losing my current one to electrical fire as well.
Last edited by youngbimmer; 05-28-2020 at 10:28 AM.
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