m50 no spark--no start

[mtech325]

Hey everyone,

So the m50 swap I'm working on won't start. Car is a 93 e30 325i Convertible if that makes a difference. The the starter won't turn over from the key/ignition, but the starter works because I've jumped pins 11 & 14 from the diagnostic port (windows/heater both work so it's wired up correctly?). The fuel pump is working as I undid one of the lines and fuel spewed out.

The big problem I'm encountering is no spark. I've tried swapping red label 413 ECU's, crank position sensor, cam position sensor, but still no luck. I feel the ECU is not getting power (but I've checked all the power/ground connections), and I've swapped the relays with other ones to check that those are in good shape as well.

The car has a Clifford G4 alarm that I wonder if it has some sort of ignition immobilizer from when it was installed by the previous owner on the m20 (hence why the starter won't turn from the key and only when jumped). Otherwise I may suspect a difference in the wiring between the e34 and e36 wiring harnesses. I had a harness adapter made for the e34 harness originally, but put in an e36 harness for fitment purposes. My research says the 1994 m50 e34 harness and the 1994 m50 e36 harness have the same pinouts, but I could be wrong. My last bet is to try swapping in the e34 harness to see if it fires. This has really got me stumped!

CLIFF NOTES: 1993 e30 325i Convertible M50 no spark/start because of difference between e34 and e36 harnesses for 24v adapter?, or old Clifford Alarm Immobilizer in ignition?

Thanks for taking the time to read this and any help is appreciated,

Joey

[e30austin]

All your grounds and power leads hooked up properly? Post some pics of your battery junction box.

[mtech325]

Here's the pictures like you asked for. There's no power distribution block since this is a convertible, so all the power wires go to the positive side of the battery (that's how it was on the m20). The two smaller wires are from the fusebox.

For the ground side, there's the battery ground itself, as well as the ground from the harness itself. I know this doesn't look too pretty, but this is what I have to work with. Perhaps I wired this up wrong. I checked the frame rail ground and it's good, as well as the ground going to the front engine hook.

Sorry for the bad cell phone pics!

[mtech325]

Bumping this from the dead. After a few months of on-and-off work, the ignition works with the key( car will crank and pump fuel), but the car still won't spark and fire up (but the car is getting fuel). My friend and I have tried 5 different 413 red label DMEs and still no luck. We have been working with an Indy BMW mechanic to troubleshoot some of the issues.

Using one of those fancy touch screen diagnostic tools, there are no faults in the DME, and all the injectors have been tested to fire. A new crank sensor was installed to rule that variable out. The main relay has been tested to work properly, and power is present going to the DME and coil pack connectors. The engine block to frame rail ground, battery ground, and harness ground near the front hook have been checked. (Maybe I'm missing an obvious ground). New battery has been put in place to ensure a good charge.

I've read about the OBC causing a no start (car has 13 button sport computer), so I've tried unplugging that, but no still no spark. Is it possible that the harness is a dud? Or is this an EWS issue (even though I've always thought red label DMEs were devoid of EWS, Turner's site says cars before 1995 have some form of it)?

This swap genuinely has me stumped. From my understanding, the DME is what tells the coil packs to fire once it gets a signal from the crank position sensor. If it makes any difference, the diagnostic tool would not get a reading of RPM with the motor cranking (supposedly it should be 300 rpm) Anyone have pointers or suggestions?

Thanks,

Joey

[e30austin]

Ever figure this out?

[SmokeE30]

We had an unloader relay fail on a m52 swap recently causing a no spark condition like that, may be worth a shot

[mtech325]

Ever figure this out?

Ok, the car does run........finally! After bringing it to a mechanic friend who is a genuine BMW whiz, he said there was an issue with the ignition feed wire. Supposedly the coils weren't being supplied enough voltage, so that's why they didn't fire. His other comment was that the wiring harness adapter was pinned wrong. According to him, the 93 vert we're working with had an early car style pinout. This confused me a bit as I thought most of the airbag cars all had similar pinouts for their respective motors (m20 and m42). Maybe the factory got lazy and started using leftover parts as this car has an 11/92 build date.

Lesson learned for me: become better at reading and identifying wiring diagrams (of course it doesn't help that I'm color blind.....)

If I had to do this again, I would probably send the harness out to Markert and have it all squared away the first time around.

Hopefully this helps someone else down the line should they run into a similar issue.

[36brua]

Yes reading the wiring diagrams is important. That is why Markert, and probably others, have you supply a pin out of the chassis side C101 --before they start the harness work.
Weophones is a great place to start for schematics.

http://wedophones.com/BMWManualsLead.htm