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Go Back   Bimmerfest - BMW Forums > BMW Model Discussions > 5 Series > E39 (1997 - 2003)

E39 (1997 - 2003)
The BMW 5-Series (E39 chassis) was introduced in the United States as a 1997 model year car and lasted until the 2004 when the E60 chassis was released. The United States saw several variations including the 525i, 528i, 530i and 540i. -- View the E39 Wiki

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  #1  
Old 04-16-2014, 09:26 PM
francisngara francisngara is offline
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Location: seattle, washington
 
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Mein Auto: 2002 530i
Melting ignition coil

Hi to you all,
I need your help,I'm working on my 2002, 530i and I kept melting my coils on cyl 5 ( 3 coil melted so far on that same spot) after a valve gasket job done on the engine; I checked all the ground wires of coils seem fine and did not have any melting coils prior to the job,but suspecting new spark plug (Bosch platinum+2) from my sold 96 328i which fitted fine on 530i might have caused the problem; worst case scenario, I might have blown the dme which controls coils. I looked the fuse behind the dme which i noticed got burned along with the first coil, I replaced my fuse and coil but I am on my third coil melting on the same 5th cylinder.however the car start even tough rattles with other 5 coils. any idea on the issue how to approach it? Thanks!
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  #2  
Old 04-16-2014, 11:29 PM
edjack edjack is offline
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Did you have the Bosch plugs in place before the valve gasket job without coil problems?

Put in a set of NGK BKR6EQUP.
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  #3  
Old 04-17-2014, 03:36 AM
francisngara francisngara is offline
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Thanks for your reply, I had the ngk plug before the job. I had a missfire on cylindre 3&5 which prompt me to replace the plug in the first place and i did replace all the 6 but using bosch plugs instead of ngk.
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  #4  
Old 04-17-2014, 06:14 AM
CitizenOfDreams CitizenOfDreams is offline
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Measure the voltage across the primary winding of coil with the key on. If you have permanent 12V across the winding, you have a bad DME output or a short in the wiring. Or both.

Since the problem started after the valve cover job, the wiring on top of the engine would be my first suspect.
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  #5  
Old 04-17-2014, 06:43 AM
Flightmedic Flightmedic is offline
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Look closely for a pinched wire serving the coils. If You were just there working and now have an electrical issue, I would look in the areas where you were just working. Often that is catching a harness under a cover edge and tightening down. Be sure to check the underside of harnesses, because it is the hidden parts that cause issues. Follow every inch from the coils back.


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  #6  
Old 04-17-2014, 09:14 AM
francisngara francisngara is offline
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Thanks for your advices, I'm going to check both the wiring and voltage going to the coil; however, right after theVCG job, I was able to drive 10 miles without issue, the melting start a day after the VCG job. So meaning that the wiring was put back as they should. I'm little convince on the idea of bad DME sending high courant to the coil but need to check the voltage prior to do anything else on the dme; wondering whether or not a DME can be repaired since other coils get appropriate voltage and I can actually start the car. Thanks you all
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  #7  
Old 04-17-2014, 04:00 PM
Flightmedic Flightmedic is offline
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Conventional wiring of engine control circuits place supply Power to the coil which is activated via grounding of the circuit. Otherwise the Supply side being thru the computer would result in failure of an entire set of coils, rather than just one.
So you should realize running voltage to the coils always with key in run position. A failure of one transistor would result in a misfire because a coil only works with current changes; thus a short causing continuous current flow will create no spark.
Which means I must admit that a pinched wire would have the same result.....
What part of the coil is melting? Could it be from a leak, as in loose spark plug? Or a cracked insulator on the plug discharging thru the boot?


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  #8  
Old 04-18-2014, 04:48 PM
francisngara francisngara is offline
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thanks y'all for your help, I'd like to let you know that I found what was the problem. the wiring harness going to coils was rubbing the exhaust manifold and one of the 6 coils wire was burned exposing the wire which was constantly touching the manifold. as result, I had ground from manifold being in contact with positif going to coils #5 melting it each time. so problem solved without any specialist looking into this and i couldn't have done it without you. so thank you from the bottom of my heart you saved me thousands.
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  #9  
Old 04-18-2014, 05:10 PM
bobdmac bobdmac is offline
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Nice to hear a good wrap-up of your problem.
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  #10  
Old 04-18-2014, 06:46 PM
CitizenOfDreams CitizenOfDreams is offline
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I'm glad your DME survived the short circuit. It's amazing what amount of abuse modern car electronics can withstand.
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  #11  
Old 04-18-2014, 06:49 PM
Flightmedic Flightmedic is offline
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It survived because the DME provides ground for circuits. The power supply is provided to the coils and triggered to ground thru the DME.


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  #12  
Old 04-18-2014, 06:57 PM
CitizenOfDreams CitizenOfDreams is offline
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nevermind, was too tired to think.

Yes, you are right, a short to ground will not put any strain on the DME outputs.

Last edited by CitizenOfDreams; 04-18-2014 at 07:01 PM.
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  #13  
Old 04-18-2014, 07:15 PM
Flightmedic Flightmedic is offline
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Genious the way those are connected in a way to save the computer, and also a failure of one coil won't take out the fuse to the whole system thus leaving us parked in the roadside.


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