*SOLVED* Bad ECU? No spark, fuel, ICV

Specific conversations and info for the BMW E28 M5 and M535i.
gcracker
Posts: 147
Joined: Jun 05, 2009 6:00 AM

Re: Bad ECU? No spark, fuel, ICV - all seem related to Motro

Post by gcracker »

tschultz wrote: ...Are you sure your coil is good? Should be easy to swap in from a different BMW of the era to test it...
Concentrate on verifying you have spark.

Then if it is still not working, verify that you have fuel...
I have two spare working coils, and also can trigger the coil at the ECU and get a strong spark. ECU will not supply spark in my car.

Fuel is being supplied on start, and if I jumper Pins 30&87 at FP relay. Injectors are not firing, but here is where it gets interesting:

When jumpering pin 30 to both pins 87 at the main relay, one of my jumpers slipped, and I heard a buzz/hum from the engine. Turns out that supplying power to both 87 pins, then removing power from the pin that supplies power to the ECU results in my evap purge valve and the injectors (perhaps not all of them?) buzzing.

Video of buzzing: https://www.youtube.com/watch?v=GBrWnXKW3cs

So confusing...
gcracker
Posts: 147
Joined: Jun 05, 2009 6:00 AM

Re: Bad ECU? No spark, fuel, ICV - all seem related to Motro

Post by gcracker »

SOLVED:
After just over 3 years of fiddling and shotgun diagnosis, the ///M5 is finally providing timing control and injector pulses!

SOLUTION:I removed and cleaned every ground related to injection/ignition/DME.

MORAL: Basics, basics, basics. When things aren't working correctly, and even when you test some things and think you confirm them, just do the work of repairing them anyway.

When I removed the G103 grounds (which, BTW, the ETM for the S38 is absolutely incorrect when claiming ECU grounds - Pins 10,16,17,19 - go to G102 on the fender), and ran a discreet ground circuit from there back to battery, I had timing control and injector pulses for the first time in three years (14 if you count disassembly for rebuild). I suspected grounds when the symptoms from my last post in this thread were occuring. that seemed like a circuit finding ground through other circuits. As it turns out, that still happens, but I am not concerned now that I have spark/fuel!!!!

I still have a problem with poor mixture and perhaps incorrect ignition timing caused by the Dinan ECU chip(?). I'll consider replacing it with the stock chip for break-in. Don't have a fuel pressure testing kit right now, so could be a poorly-operating high-pressure pump. When it's cranking, right now you can tell there is some pre-ignition that almost spins the motor backwards. Could even be two year old fuel preigniting from compression.

Anyway, it LIVES!!!! Off to register it as an antique exempt from state inspection now.

Thank you to all who helped me get to this point, especially @Ahab, for taking the risk of installing my ECU in his beloved ///M5 to test that mine was still working.
ahab
Posts: 6174
Joined: Jun 11, 2006 9:12 AM
Location: Chalfont, PA

Re: *SOLVED* Bad ECU? No spark, fuel, ICV

Post by ahab »

Holy shit. I had forgotten about this thread. Glad to hear you got it (mostly) sorted out. Regarding the poor running, I think you are on the right track with the fuel. I doubt it's the Dinan chip specifically causing the problem. I have been down this road with an engine that sat for long periods of time and the Dinan chip was never my issue. Old fuel and/or gummed fuel delivery components from the old fuel have been a problem. Vacuum leaks as well.

Good luck!
gcracker
Posts: 147
Joined: Jun 05, 2009 6:00 AM

Re: *SOLVED* Bad ECU? No spark, fuel, ICV

Post by gcracker »

ahab wrote:Holy shit. I had forgotten about this thread. Glad to hear you got it (mostly) sorted out. Regarding the poor running, I think you are on the right track with the fuel. I doubt it's the Dinan chip specifically causing the problem. I have been down this road with an engine that sat for long periods of time and the Dinan chip was never my issue. Old fuel and/or gummed fuel delivery components from the old fuel have been a problem. Vacuum leaks as well.

Good luck!
Yep. It was the fuel. The injectors got all messed up from the old fuel, so I sent them to Cruzin for a refresh. I am using this mistake as a driver to drop the tank and do the POR-15 fuel tank repair on it, since it has some weeping at them seams. I'll also either replace the fuel lines or clean them up with solvent prior to activating the pumps again. Hopefully, my cat is okay. It got red hot with the fuel issues...

Thanks for your help!
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