Seeking experts. No spark / no start S38 M5

[airkhin]

resolution was ecu. fired right up with a test unit.

Any one have an b36 unit around or recommend repair service? Thanks!

[Jackson42]

Chances are it can be repaired. Over the course of many heating/cooling cycles, the solder joints form almost microscopic cracks around the leads of the driver transistors on the printed wiring board assembly. I've fixed more than one of them by simply reflowing the solder on the power semiconductors. Easy to do if you're handy with a soldering iron and if it doesn't fix the problem, you're not out anything but a little time.

[demetk]

I've done the same on many of them over the years. Get yourself an electron microscope and the cracks will be clearly visible.

[Jackson42]

Check Dovebid for the electron microscope - it's been a long time since I've seen a good one for sale on eBay.

[myeshia91]

Could it be a failed coolant temp sensor (blue sensor) causing the engine to flood? The sensor is relatively inexpensive, easily accessible on the s38 and may be worth a try.

Also, when I had no-start/flooding issue on my e34 touring, it turned out to be a combo of a bad fuel pressure regulator and leaking fuel injectors. When the engine flooded, I had to clear the excess fuel by pulling the fuel pump fuse and starting the car a couple of times. I would then replace the fuel pump fuse and the car would start as normal. A new FPR and new injectors solved the problem completely.

I think I'm having this issue with my 94 525i. No-start. Spark plugs were black, oil dipstick smells of gas. I will replace the regulator and see if any injectors are leaking.

[SpecRaceM5]

I wish I had a spare ECU I could provide but unfortunately that's one of the few spares that I do not have. Since yo are somewhat local to the Bay Area, you might try reaching out to motatti if you happen to know him. If not, I can ask for you. He may have a spare or a place to refurbish yours.

For future reference, since you had fuel and no spark, it shouldn't have anything to do with alarms, imobilizers or OBC codes. That would be poor design as it's just going to flood your engine if they allowed fuel but no spark. Once you verified no spark, the next steps would be to check that the coil has good power, signal and ground. I don't know exactly how the ECU controls it off the top of my head but I imagine you would have good power and ground but your signal is likely shot. From there you can check the signal coming out of the DME to eliminate the wiring and condemn the ECU.

Shoot me a PM if you would like help looking for an ECU/refurbisher.

Brian

[mottati]

I wish I had a spare ECU I could provide but unfortunately that's one of the few spares that I do not have. Since yo are somewhat local to the Bay Area, you might try reaching out to motatti if you happen to know him. If not, I can ask for you. He may have a spare or a place to refurbish yours.
Brian

We used the dme out of my 3.6 to test his, and the car fired right up. I unfortunately cleared out a bunch of spares when i sold my first 3.6 a few years ago, so no extra parts on hand.

I recommended Greg at Bavarian restoration to go over his DME. Do you have any other sources?

[airkhin]

We used the dme out of my 3.6 to test his, and the car fired right up. I unfortunately cleared out a bunch of spares when i sold my first 3.6 a few years ago, so no extra parts on hand.

I recommended Greg at Bavarian restoration to go over his DME. Do you have any other sources?

Yep, greatly appreciate the responses, (and help from mottati), sent my dme to Greg a few days ago, will keep posted with results. in the down time maintenance work continues...

[SpecRaceM5]

We used the dme out of my 3.6 to test his, and the car fired right up. I unfortunately cleared out a bunch of spares when i sold my first 3.6 a few years ago, so no extra parts on hand.

I recommended Greg at Bavarian restoration to go over his DME. Do you have any other sources?

I haven't gone through this yet so no one to my knowledge. I used Module Masters, which is somewhere in the mid west or back east I think, for my moms ABS control module in her old E39. Don't know that they would be able to touch this though.