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Ignitions burning


Ronny

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Hi

Recently got a wierd missfire that got progresivly worse until finally 2 coils caught on fire filling the garage with smoke. The ignitor used was a fueltech sparkpro-6 and that also gave up the ghost, so I decided to use bmw z4/ toyota supra coils instead of standard M50 coils and I used 2x Bosch 0227100203 ignitors. Car started up and ran fine for about 30 min then missfires came back and the ignitors are real toasty maybe even destroyed. This makes me wonder if maybe my old trusty g4 extreme is the culprit... Anyone else had this problem?

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The dwell times used was the ones suggested for the fueltech unit, after the switch to the b58 (supra/z4) coils i set the whole dwell table to a conservative 2.3ms just to make sure the coils wouldnt fry. coils didnt get very hot and I have tried to start it later now in the afternoon and its now a 3 cylinder bmw m50... one of the ignitors are fried. That and the fueltech unit getting toasted after running good for almost a year then suddenly not, makes me wonder if the ecu is on its way out. Does anyone know of a way to test it?

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It matches according to the last log file I had with the FT ignitor still in the car. when the missfires started I decided that it was time to replace the crank sensor and cam sensor while I also installed pressure/temp sensors for oil, water and fuel. And now also new coils and ignitors. All cables for the ignition is twisted motorsport wire kept well away from any other wires to prevent interference. Grounds are checked and good. I just dont know what else to do. The car ran fine and then all of a sudden it decided to start frying ignition componenets.

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So... the doomsday scenario of it running on 3 seems to be exaggerated, it thinks its an audi so it runs on 5... ign out 2 is the problem tested all out puts and 2 was dead, flipped the ignitor contacts and 2 was sparking fine and 5 was dead. same thing that happened to the FT ignition. measured ign2 and compared it to ign1 and 3 saw no difference between them. I don´t have access to an osciloscope and even if I did I wouldnt know how to use it... Any suggestion is welcome.

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A cheap LED test light is a good tool to verify Ign output.  It does sound like you may have a fried one. 

With the ignitor disconnected connect the testlight to ground at one end and the ign output at the other.  Put ign in test most and you should see a small flash on the testlight - quite a short flash so best to see in a darker area - or at least not in direct sunlight.  

You want something really basic like this example, not one of the ones with LCD screen etc:  https://www.amazon.com/WINAMOO-Premium-Automotive-Extended-Circuits/dp/B08D9RY532  Most autoparts stores will have something similar.  

If the ign output has failed it can likely be repaired. 

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  • 1 month later...

put in a g4x extreme and another igniter got fried instantly so I'm thinking my old g4 ecu is not the problem. Replaced the ignitors and all the coils got upgraded to bosch motorsport p65 coils and also rewired all of the ignition. It started instantly and idles ok, but me being a little concerned with all things ignition at the moment decided to check the temps on the igniters and the were real hot. Even with the bosch recomended dwell times so I checked the dwell table and it seems my ecu is only seeing around 8 volts from time to time and extends the dwelltime.

Could it be a bad ecu ground making it think system voltage is only 8 volts and bumping up the dwell even though the coils and ignitors are seeing 12-14 volts? I imagine that would cause the components to overheat.

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log the system voltage and the dwell time , should become obvious very fast if it does.

practically i would assume there's a bad ground on the engine causing the ecu voltage to read lower

do some basic voltage drops test on powers and ground while the engine is running (and even out the dwell table temporarely to stop your coils from melting)

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Checked the battery voltage and its a healthy 12.9 volts according to my DVM, the E46 cluster test menu says the same. Pierced the supply wires for the ecu and that gives the same reading. Also  hooked up a 90mm² ground for the engine so that shouldnt be an issue. Still my ecu says battery voltage is around 8.5 - 10 volts and the igniters are getting hotter then Megan fox in transformers, dwell is set to 2 ms across the board so that shouldnt be a problem. I did measure the ecu ground cables and they had around 20 and 30 ohms of resistance between ecu connector and engine. Could this be the reason its showing low voltage? Watched a HP Academy youtube episode about star grounding and there was a mention of random triggering of outputs when ecu ground was bad, could that be the case? The Fueltech ignition got fried when the car was sitting with key on but engine off. This is getting realy annoying since the electronics worked great and then I pulled the motor and rebuilt it and after that all sorts of electronic gremlins are showing up.

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19 hours ago, Ronny Lidman said:

I did measure the ecu ground cables and they had around 20 and 30 ohms of resistance between ecu connector and engine.

An acceptable connection would be less than 1ohm.  You have a very poor connection somewhere.  

This large resistance will likely cause enough ground offset that your ignitors will see a high signal and start charging the coils randomly as electric loads change.   

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Tried replacing the grounds today and now after half an hour on idle while tinkering with random stuff the igniters are still cold. So the ignition frying seems to be resolved but the ecu still only see around 10 - 11 volts even if the battery is att 13.3, voltage drops down to 8 - 9 volts in pclink when i give it some revs... The wiring harness is the same old harness i bought when i first got my g4 red extreme, so maybe its time to retire it and get a new one. 12 volt feeds have been replaced recently though so its wierd it shows low voltage with new feeds and grounds. and what could be the reason for the voltage drop when giving it some revs?

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The ecu measures voltage between pin A5 and A34.  I would start by backprobing these pins and measure the voltage here with a voltmeter while running to confirm if there is a voltage issue there.  To backprobe, push a pin or needle or similar in through the connector seal along side the wire until it makes contact with the terminal inside, example using a sewing pin below.

4FVQCMZ.jpeg

  

 

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backprobing showed 14.05 volts, so the new grounds only solved part off my problem, but since i can have the car running for awhile without destroying ignition components I logged it. seems like voltage drops when TPS move just a tiny bit.

PC Datalog - 2022-12-14 7;59;11 pm.llgx bmw 320.pclx

*edit*

Took the ecu out of the car and bench tested it and my old g4 red, using a stable power supply. When no sensors or auxilary stuff is connected they both track the voltage perfectly in their respective pclink. This leads me to think something is wrong with the harness or a sensor. Would that make any sense? 

Edited by Ronny Lidman
Further investigation
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7 hours ago, Ronny Lidman said:

Took the ecu out of the car and bench tested it and my old g4 red, using a stable power supply. When no sensors or auxilary stuff is connected they both track the voltage perfectly in their respective pclink. This leads me to think something is wrong with the harness or a sensor. Would that make any sense?

Still sounds like a ground issue to me.  I cant see how an aux or sensor would effect the battery voltage or ecu power supply.  Aux load goes through ground though so if there was a weak ground connection any aux load could offset the ground in the higher direction.  

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  • 1 month later...

Made a new wiring harness and replaced any and all things related to the electrical system for the engine. Turns out the m6 bolt for the grounds to the cylinder head was loose... I now have a good reading of the voltage that tracks the cluster and my dvm perfectly.

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